Et(gautam)
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ET - 2nd MID -
-
JNTU ONLINE EXAMINATIONS [Mid 2 - ET]
1.
Which of the following determines the direction of the induced emf in the stator just before it begins rotate? a. Fleming's right hand rule b. Kirchoff's law c. Lenz's law d. Ohm's law
2.
The rotating field caused by the stator current induces EMF in the rotor by a. Transformer action b. DC machine action c. Synchronous machine action d. AC machine action
3.
Induction motor works on the principle of a. Mutual induction b. Ampere's law c. Lenz's law d. Ohm's law
4.
The magnitude of rotating magnetic field is equals to a. 1.5 X maximum flux density b. 3X maximum flux density c. 2 X maximum flux density d. Maximum flux density
5.
The rotor speed of induction motor is always slightly a. Less than synchronous speed b. More than synchronous speed c. Less than slip speed d. More than slip speed
6.
The operating speed of induction motor never be equal to a. Synchronous speed b. Slip speed c. Stator speed d. Speed of magnetic field
7.
The induction motor draws balanced three phase current, when it is connected across a a. Balanced three phase ac supply b. Balanced single phase ac supply c. Balanced three phase dc supply d. Balanced dc supply
8.
The direction of rotation of rotating magnetic field gets reversed, when a. Interchanging any two terminals of stator windings b. Interchanging any three terminals of stator windings c. Interchanging any two terminals of rotor windings d. Applying supply voltage to rotor windings
9.
The magnitude of rotating magnetic field is a. Constant b. Not constant c. Varying d. Rotating
10.
An a. b. c. d.
Induction motor is Self-starting with low torque Self-starting with zero torque Self-starting with high torque Non- Self starting
11.
The skewed at a desired angle of the rotor slots in squirrel cage induction motor results a. uniform torque and avoid magnetic locking b. non uniform torque and avoid magnetic locking c. uniform torque and magnetic locking
ET - 2nd MID -
d.
-
non uniform torque and magnetic locking
12.
The skewed at a desired angle of the rotor slots in squirrel cage induction motor results a. Reduce humming noise b. increase humming noise c. Non uniform torque d. un avoid magnetic locking
13.
The coil wound rotor must be wound for the same number of poles as that of a. stator b. rotor c. armature d. field
14.
The rotor winding of a squirrel cage induction motor is a. solid un insulated conductors b. similar to the stator winding c. solid insulated conductors d. laminated base conductors
15.
The starting torque of three-phase slip ring induction motor is high because a. Rotor is phase wound b. Rotor resistance is low c. Rotor resistance is zero d. Rotor has short - circuited
16.
The number of slip rings on a squirrel cage induction motor is usually a. Zero b. Two c. Three d. Four
17.
The windings of wound rotors are similar to a. stator windings b. rotor windings c. armature winding d. field winding
18.
The rotor of the squirrel cage induction motor is also called a. Short circuited rotor b. Open circuited rotor c. Open ended rotor d. Stationary rotor
19.
In a. b. c. d.
20.
The three phase winding on the rotor of slip ring induction motor is connected in a. Star b. Delta c. Series d. Parallel
21.
The speed near to the synchronous speed the torque-speed and torque-slip curves are approximately a. Straight line b. Parabola c. Hyperbola d. A curve
22.
The maximum torque in an induction motor depends on a. Square of the supply voltage, frequency, rotor reactance b. Square of the supply current, frequency, rotor reactance c. Square of the supply voltage, frequency, rotor resistance d. Square of the supply current, rotor reactance
a squirrel cage induction motor, the stationary current is 5 to 7 times the rated current Equal to the rated current Double the rated current Half the rated current
ET - 2nd MID -
-
23.
For a slip greater than 0.1 Pu, torque T varies inversely as a. slip b. rotor resistance c. stator resistance d. rotor reactance
24.
The maximum running torque is a. Independent of rotor resistance b. Dependent of rotor resistance c. Dependent on slip d. Independent of rotor frequency
25.
The maximum torque is also called a. Pull-out torque b. Starting torque c. Running torque d. Stator torque
26.
In a. b. c. d.
27.
The torque T developed by induction motor is directly proportional to a. slip, for lower values of S b. slip for higher values of S c. rotor resistance d. stator resistance
28.
The condition for the maximum torque occurs when the slip is equal to a. ratio of rotor resistance and leakage reactance b. ratio of leakage reactance to rotor reactance c. rotor resistance d. leakage reactance
29.
The torque is zero, when a. Slip is zero b. Slip is unity c. Slip is infinity d. Slip is 0.5
30.
The value of the maximum torque is independent of a. rotor resistance b. stator resistance c. rotor reactance d. leakage reactance
31.
The power developed at the shaft is equal to a. Difference of gross mechanical power and mechanical losses b. Difference of input power and output power c. Difference of input power and mechanical power d. Difference of input power and mechanical losses
32.
A 420v, 50Hz, 6-pole, 3- phase induction motor has rotor power input of 80kw. The slip is 3.3 %, then the mechanical power developed is a. 77.33kw b. 154.66kw c. 2.64kw d. 26.4kw
33.
The power input to a 6-pole, 3-Ø, 50Hz induction motor is 40kw. Stator loss is 11kw, and the slip is 45. Then the rotor copper losses are a. 1.56kw b. 1.6kw c. 15.6kw d. 16kw
34.
The rotor core loss is negligible, because
case of induction motor the torque is Directly proportional to slip Inversely proportional to slip Directly proportional to square of the slip Inversely proportional to square of the slip
ET - 2nd MID -
a. b. c. d.
-
The frequency of rotor current is small under running conditions The frequency of rotor current is high under running conditions The frequency of stator current is small under running conditions The frequency of stator current is high under running conditions
35.
The power factor of three - phase induction motor at no - load is a. 0.1 b. 0.5 c. 0.6 d. Unity
36.
In a. b. c. d.
37.
The slip of the induction motor is also defined as the ratio of a. Rotor copper loss to rotor input b. Rotor input to rotor copper loss c. Air gap power to rotor input d. Stator copper loss to rotor input
38.
The fractional slip of an induction motor is the ratio of a. Rotor copper loss to rotor input b. Stator copper loss to stator input c. Rotor copper loss to rotor output d. Rotor copper loss to stator copper loss
39.
The input power to the rotor is usually called a. Air gap power b. input power c. out put power d. mechanical power
40.
In a. b. c. d.
41.
In case of star- delta starter, the voltage applied across the winding is a. 1/ times the line voltage
an induction motor the core losses occur mainly in Stator core Armature core Slip rings Brushes
induction motor, the maximum efficiency occurs, when Variable losses equal to constant losses Variable losses are equal to zero Constant losses are equal to zero The total losses equal to zero
b. c. d. 42.
times the line voltage 3 times the line voltage 1/3 times the line voltage
In case of star- delta starter, the starting torque is a. 1/3 times the full-load torque b. 1/ times the full-load torque c. d.
3 times the full-load torque
43.
In a. b. c. d.
case of induction motor, the starting current drawn from the supply is about Four to seven times the full-load current Ten to twelve times the full load current Four to seven times the no load current Ten to twelve times the no load current
44.
In case of auto transformer starting transformation ratio K=1/
times the full-load torque
starting method corresponds to a. Star-delta starting b. DOL starting c. Resistance starter d. Rotor resistance starter 45.
The rotor resistance starter reduces
, this
ET - 2nd MID -
a. b. c. d.
-
The magnitude of starting current The magnitude of applied voltage The magnitude of starting speed The magnitude of starting torque
46.
The induction motor is a a. Self starting motor b. Not self starting motor c. Coupled to other drive d. Coupled to other drive
47.
The Rotor resistance starter improves the a. Starting power factor b. Starting current c. Starting voltage d. Starting resistance
48.
The three-phase induction motors up to 5hp can be started by a. Direct on line starter b. Star-delta starter c. Auto transformer starter d. Resistance starter
49.
The star- delta starter is used for a. Squirrel-case Induction motor b. Slip-ring Induction motor c. Phase-wound Induction motor d. Double cage Induction motor
50.
n an squirrel cage induction motor, the starting torque is very low because a. The rotor resistance is small b. The rotor reactance is small c. The rotor resistance is high d. The rotor reactance is high
51.
The salient pole construction is employed for synchronous machines having a comparatively a. Low output and slow speeds b. Large output and slow speeds c. Low output and high speeds d. Large output and high speeds
52.
Three-phase alternators are usually star connected a. To save on copper b. To reduce windage losses c. To reduce conductor size d. To obtain higher terminal voltage
53.
The stator of alternator is made of high permeability laminated steel stampings in order to reduce a. Hysterisis and eddy current losses b. Copper losses c. Mechanical losses d. Friction and wind age losses
54.
The salient type rotor is also called a. Projected type b. Cylindrical type c. Conical type d. Spherical
55.
The function of the winding on the rotor of an alternator is a. To produce flux in the air gap b. To produce torque in the air gap c. To produce induced EMF in the air gap d. To produce current in the air gap
56.
The non-salient type rotor is also called a. Cylindrical type b. Projected type c. Conical type
ET - 2nd MID -
d.
-
Spherical type
57.
The rotor of alternator is constructed from laminated high permeability steel in order to reduce a. Eddy-current losses b. Hysterisis losses c. Copper losses d. Friction and wind age losses
58.
The coupling between the electric and mechanical systems is through the medium of a. Electromagnetic field b. Electric field c. Mechanical field d. Electrostatic field
59.
In a. b. c. d.
60.
The speed of a 4-pole 60Hz synchronous machine will be a. 1800rpm b. 1500rpm c. 3000rpm d. 3600rpm
61.
The number of cycles of the induced EMF depends on a. The number of poles b. Number of conductors c. Number of slots d. Number of rotations
62.
The integral number of slots per pole is often used in order to eliminate a. Harmonics in the wave form b. Copper loss c. Core loss d. Friction and wind age loss
63.
An a. b. c. d.
64.
Synchronous generators are used to generate a. Only alternating current b. Only direct current c. Both alternating and direct current d. Either alternating and direct current
65.
The EMF generated in an alternator is a. Average value b. Maximum value c. RMS value d. Virtual value
66.
In a. b. c. d.
67.
EMF generated in an alternator depends upon a. Flux per pole, no. of conductors b. Slip and no. of conductors c. Slip and rated speed d. Flux per mole and rated speed
68.
a rotary machine the purpose of an air gap is to Reduce the mmf required Provide a path for the flux Allow for rotation of the rotor Improve the reluctance
exciter is nothing but a DC shunt generator DC series motor DC shunt motor DC series generator
a Non-salient pole machine The rotor is cylindrical and air gap is uniform The rotor is cylindrical and air gap is non-uniform The rotor is Non-cylindrical and air gap is uniform The rotor is Non-cylindrical and air gap is non-uniform
In an alternator
ET - 2nd MID -
a. b. c. d.
-
The conductors are stationary and field is rotating The conductors are rotating and field is also rotating The conductors are stationary and field is also stationary The conductors are rotating and field is stationary
69.
The alternators work on the principle of a. Electromagnetic induction b. Electrostatic induction c. Lenz's law d. Ampere's law
70.
Alternator will convert a. Mechanical energy into electrical energy b. Electrical energy into Mechanical energy c. Mechanical energy into rotating energy d. Mechanical energy into heat energy
71.
Turbo-alternators are generally used to turn at a. 3000rpm b. 1500rpm c. 5000rpm d. 15000rpm
72.
The open type of slots are preferable for use in alternators because a. They easily accommodate the winding b. Their use is less costlier c. They provide wave form d. Their use gives uniform flux distribution
73.
The salient pole type of alternator is also called a. Projected pole type b. Non-salient type c. Cylindrical type d. Un projected type
74.
Salient pole alternators are generally used on a. Low and medium speed prime movers b. Low voltage alternators c. Hydrogen cooled prime movers d. High speed prime movers
75.
In a. b. c. d.
76.
The cylindrical type of alternator is also called a. Non-salient type b. Salient type c. Projected pole type d. Un projected type
77.
Salient pole alternations are used, when a. The speed of the alternator is low b. The power required is large c. The speed of the alternator is high d. The voltage to be generated is high
78.
The advantage of cylindrical type rotor of an alternator is a. Low wind age losses and better balance b. Low copper losses and better balance c. Smooth operation and low core losses d. Less air friction and low variable losses
79.
The rotor preferred for alternators applied to hydraulic turbines are a. Salient pole type b. Cylindrical pole type c. Solid rotor type
a Non-Salient pole machine, the rotor is Cylindrical and air gap is uniform Cylindrical and air gap is non-uniform Non-Cylindrical and air gap is uniform Non-Cylindrical and air gap is non-uniform
ET - 2nd MID -
d.
-
Non-salient type
80.
The cylindrical rotor machines have always a. Horizontal configuration b. Vertical configuration c. Both Horizontal and Vertical configurations d. Either Horizontal or Vertical configurations
81.
In a. b. c. d.
which coil the harmonic component of the generated EMF will be more? Full pitch coil Short pitch coil Long pitch coil Same in all coil
82.
In a. b. c. d.
an alternator, if the air gap flux density is non-sinusoidal, then the EMF generated contains Harmonics Composite wave form of voltage and current Only current wave form Only voltage wave form
83.
By to a. b. c. d.
distributing the winding of an alternator into number of slots, the generated EMF can be made
84.
In a. b. c. d.
an alternator the resultant EMF per turn will be Twice the EMF induced in a conductor Equals the EMF induced in a conductor Half the EMF induced in a conductor Thrice the EMF induced in a conductor
85.
To a. b. c. d.
generate sinusoidal EMF's, the special flux distribution in the air gap must be sinusoidal Rectangular Triangular Elliptical
86.
In a. b. c. d.
an alternator the average EMF per phase is equal to 4.44 f Ø T volts 4.44 B T volts 4.44 f B volts 4.44 f T
87.
The EMF equation of an alternator( if the winding for each phase under each pole is distributed) is a. 4.44 f Ø T kc k d volts b. c. d.
Reduce Increase No change Reduce or increase
4.44 f Ø T volts 4.44 f Ø T k c volts 4.44 f Ø T kd volts
88.
A 4 pole, 1500rpm alternator will generate EMF at the frequency of a. 50 Hz b. 60 Hz c. 40 Hz d. 25 Hz
89.
If a. b. c. d.
the speed of alternator is increased the EMF generated will Increase Decrease Remains same No change
90.
In a. b. c.
an alternator, the EMF generated is due to Rate of change flux linkages Transformer action Relative motion between conductors and the field
ET - 2nd MID -
d.
-
Electro static induction
91.
The pitch factor is defined as the ratio of the voltage generated in a a. Short pitch coil to the voltage generated in a full pitch coil b. Long pitch coil to the voltage generated in a full pitch coil c. Short pitch coil to the voltage generated half pitch coil d. Long pitch coil to the voltage generated half pitch coil
92.
The advantage of a full-pitched coil span is that it provides a. Higher generated EMF b. Lower armature current c. Lower terminal current d. Higher full-load current
93.
The winding factor is equal to a. Product of distribution and power factors b. Ratio of distribution and power factors c. Ratio of power and distribution factors d. Sum of distribution and power factors
94.
The coil span is defined as a. The separation between coil sides of the same coil b. Separation between two consecutive coils c. Separation between coil ends of the same coil d. Separation between coil ends of different coils
95.
For short pitch and distributed winding, coil span factor and distribution factor are always a. Less than unity b. Greater than unity c. Equals to unity d. Equals to zero
96.
The short-pitched coil means a. The coil span is less than full pitch b. The coil span is less than half pitch c. The coil span is less than quarter pitch d. The coil span is equal to full pitch
97.
Short-pitched coils are employed to a. Save conductor material and reduce high frequency harmonic content b. Save conductor material and increase high frequency harmonic content c. Increase overhang d. Improve the wave form of the generated phase voltage
98.
The voltage generated in a full pitch coil is equal to a. Twice the coil side voltage b. Thrice the coil side voltage c. Coil side voltage d. Half the coil side voltage
99.
The breadth factor is also named as a. Distribution factor b. Pitch factor c. Power factor d. Loss factor
100.
The distribution factor is always a. Less than unity b. Greater than unity c. Equals to unity d. Equals to zero
101.
In a. b. c. d.
102.
In case of synchronous impedance method the synchronous impedance determined at short
synchronous impedance method, the armature reaction effect is replaced by Equivalent voltage drop Equivalent mmf Equivalent reactance drop Equivalent resistance drop
ET - 2nd MID -
-
circuit condition is too large due to a. Low degree of saturation b. High degree of saturation c. Medium degree of saturation d. No saturation 103.
The synchronous impedance method can be used for a. Very high capacity alternators b. High capacity alternators c. Low capacity alternators d. Medium capacity alternators
104.
The synchronous reactance of an alternator a. Equivalent reactance representing the armature reaction and leakage reactance b. A false reactance c. A reactance which is fictitious d. Equivalent leakage reactance
105.
The regulation obtained by synchronous impedance method is generally a. Higher than the actual value b. Lower than the actual value c. Equal to actual value d. equal to zero
106.
The synchronous impedance method is used to determine a. Regulation of cylindrical rotor synchronous machine b. Regulation of salient pole synchronous machine c. Regulation of projected type synchronous machine d. Regulation of DC machine
107.
The synchronous impedance method is a. Pessimistic method b. Optimistic method c. Equality method d. Used for salient pole machines
108.
The synchronous impedance method is also called a. EMF method b. Ampere method c. MMF method d. Zero power factor method
109.
When there is no saturation, the synchronous impedance is a. Constant b. Reduces c. Increases d. Varies
110.
The synchronous impedance varies with a. Load and power factor conditions b. Only load conditions c. Only power factor conditions d. Terminal voltage conditions
111.
The open circuit characteristics of an alternator resembles a. B-H curve of magnetic material b. B-H curve of insulating material c. Speed torque characteristics of DC motor d. Load characteristics of DC generator
112.
The following test results are not affected by the variation in the speed of an alternator a. Short circuit test b. Open circuit test c. Short circuit and Open circuit tests d. Synchronous impedance method
113.
The synchronous impedance of an alternator is high at a. Lower excitations b. Higher excitations
ET - 2nd MID -
c. d.
-
Zero excitation Very high excitations
114.
The synchronous impedance of an alternator is low at a. Higher excitations b. Lower excitations c. Zero excitation d. Very low excitations
115.
The regulation of an alternator can be predetermined by conducting a. Open circuit and short circuit tests b. Open circuit test only c. Short circuit test only d. Load test
116.
The open circuit and short circuit tests are performed on a three-phase generator to determine a. Synchronous reactance b. Synchronous resistance c. Field resistance d. Field reactance
117.
The open circuit characteristic is plotted with a. Field current Vs phase voltage b. Field current Vs Line voltage c. Field current Vs phase current d. Field current Vs line current
118.
The short circuit characteristics of an alternator is a a. Straight line b. Parabola c. Hyperbola d. Semi-circle
119.
The magnetization characteristic of the generator is also called as a. Open circuit characteristics b. Short circuit characteristics c. Load characteristics d. Starting characteristics
120.
The short circuit ratio is a. Inversely proportional to the synchronous reactance b. Directly proportional to the synchronous reactance c. Inversely proportional to the synchronous resistance d. Directly proportional to the synchronous resistance
121.
The single-phase induction motors are not self-starting, because a. There is no relative motion between the stator and motor magnetic fields b. The magnitude of the flux produced in stator is low c. No voltage is induced in the rotor circuit d. Zero magnetic flux in rotor
122.
In a. b. c. d.
123.
The backward rotor slip in an induction motor is equal to a. (2-S) b. (1-S) c. S d. (S-1)
124.
In a. b. c. d.
case of double revolving field theory, a field can be resolved into two equal fields Rotating in opposite directions with equal angular velocities Rotating in same directions with equal angular velocities Rotating in opposite directions with unequal angular velocities Rotating in same directions with unequal angular velocities
case of single coil carrying an alternating current, the flux in air gap is Pulsating Rotating Constant Revolving
ET - 2nd MID -
-
125.
Single phase induction motor has no self- starting because a. The transformer EMF is induced in the rotor at stand still producing zero net torque b. Stator flux is pulsating c. No revolving field in the rotor d. No EMF induced in the motor
126.
The starting characteristics of single phase induction motors are described qualitatively by a. Double revolving field theory b. Rotating field theory c. Static field theory d. Magnetic field theory
127.
In case of single phase induction motor the torque produced by the forward and backward fields are a. Equal and opposite b. Equal c. Unequal and opposite d. Unequal
128.
The speed of rotation of the two magnetic fields is a. 120 f/p b. 240f/p c. 120p/f d. 240 p/f
129.
The torque developed by a single phase motor at starting is a. Zero b. More than the rated torque c. Less than the rated torque d. Rated torque
130.
The single-phase induction motor operate at a. Low power factor b. High power factor c. Unity power factor d. Medium power factor
131.
The single phase induction motor used in ceiling fan and table fan is a. Capacitor start and run motor b. Capacitor start motor c. Capacitor run motor d. Split phase motor
132.
If a. b. c. d.
133.
The capacitor start motors produce a. Very high starting torque b. Low starting torque c. Minimum starting torque d. Starting torque is zero
134.
In a. b. c. d.
135.
The capacitor in the starting winding of the single phase induction motor improves a. The power factor b. The starting current c. The starting voltage d. The starting reactance
136.
The main advantages of a capacitor run motor is a. It not only provides starting torque and also improves the power factor
the capacitor of a single phase motor is short circuited The motor will not start The motor will burn The motor will run in reverse direction The motor will run in the same direction at reduced rpm
case of capacitor start and capacitor run motors Capacitor remains in the circuit permanently Capacitor remains in the circuit temporarily Inductor remains in the auxiliary winding Resistor remains in the auxiliary winding
ET - 2nd MID -
-
b. c. d.
It is cheap It provides the starting torque It is easy to manufacture
137.
In a. b. c. d.
case of capacitor start single phase induction motor A capacitor of high value is only used for starting A capacitor of low value is only used for starting A capacitor of high value is only used for improving power factor A capacitor of low value is only used for improving power factor
138.
The stator winding of single phase induction motor is also called a. Main winding b. Auxiliary winding c. Starting winding d. Rotor winding
139.
The auxiliary winding of single phase induction motor is also called a. Starting winding b. Main winding c. Rotor winding d. Stator winding
140.
In case of capacitor start induction motors the phase difference between main current and starting current a. Almost 900 b. Less than 600 c. Equal to zero d. Between 200 to 40 0
141.
The A.C. servo motor is basically a. Two-phase induction motor b. Single phase induction motor c. Three phase induction motor d. DC motor
142.
In a. b. c. d.
143.
The main difference between a control transmitter (CX) and a control transformer (CT) is a. Electrical angle is different in addition to the air gap being uniform b. Air gap is less in the case of CT c. Air gap is more or less uniform in the case of a CT d. Electrical angle is different
144.
Permanent magnet tachometers are a. Compact, efficient and reliable b. Bulky, efficient and reliable c. Compact, low efficient and reliable d. Compact, efficient and non-reliable
145.
In a. b. c. d.
DC Tachometer, the high inertia of the rotor can be reduced by Iron less rotor Iron rotors Iron less stator Iron stator
146.
AC a. b. c. d.
serve motors are best suited for Low power applications High power applications Medium power applications Very high power applications
147.
Servo motors work on the principle of a. Transformer b. An induction motor
case of photo electric tachometer the number of pulses generated depends up on The number of holes in the disc and speed The speed only The applied voltage The input power
ET - 2nd MID -
-
c. d.
Lenz's law Ampere's circuit law
148.
In a. b. c. d.
servo system the output is A mechanical variable, like position, velocity or acceleration An electrical variable, like voltage, current or power An electrical variable, like, charge, flux or resistance A mechanical variable, like length, time or precision
149.
Ac a. b. c. d.
servo motors are not suited for High power applications Low power applications Very low power applications Medium low power applications
150.
An electro mechanical unit which generates an electrical output proportional to the speed of the shaft is called a. Tachometer b. Servo motor c. Synchro d. Single phase commutator motor
151.
A machine has a distributed 3-phase winding on stator and a Two-pole single phase winding on rotor is called a. Synchro b. Ac servo motor c. Dc motor d. Induction motor
152.
The holding torque of the stepper motor a. Increases with the exciting current b. Decreases with the exciting current c. Increases with the speed d. Decreases with the voltage
153.
The synchros are a. Self - Synchronizing machines b. Dc machines c. Induction machines d. Static machines
154.
The motor used in computer printers is a. Stepper motor b. Dc shunt motor c. Dc series motor d. Induction motor
155.
The motors used for adding and subtracting rotary speeds are a. Synchros b. Tacho generators c. Dc motors d. Ac motors
156.
A stepper motor a. Does not rotate continuously b. Does rotate continuously c. Runs at very high speeds d. Runs at very low speeds
157.
The following motor is an incremental motion motor a. Stepper motor b. Induction motor c. Dc motor d. Ac motor
158.
The stepper motor is a special type of a. Synchronous motor b. Dc motor c. Hysterisis motor
ET - 2nd MID -
d.
-
Repulsion motor
159.
A synchro is a. Miniature Dc machine b. Miniature Ac static machine c. Miniature Ac induction machine d. Miniature Ac Dynamic
160.
The synchros are used for a. Error detection b. servo mechanism for voltage Transmission c. Rotating speeds d. current detection
161.
The frequency of two phase AC servo motors varies from a. 50 Hz to 400 Hz b. 1 Hz to 50 Hz c. 400 Hz to 700 Hz d. 700 Hz to 1000 Hz
162.
The following motor have the slope of Torque- Speed characteristic is negative a. Ac servo motor b. Dc motor c. Induction motor d. Synchronous motor
163.
The servo motor has characteristic of a. High torque at all speeds including zero speed b. low torque at all speeds including zero speed c. Medium torque at all speeds including zero speed d. No torque at all speeds including zero speed
164.
The torque- speed characteristic of Ac servo motor is a. Linear b. Non- Linear c. Parabolic d. Hyperbola
165.
The servo motors consume power from a. A fraction of watt up to a few 100watts b. A fraction of watt up to a 1 watt c. 1000 watts to 1 mega watt d. 100 watts to 1000walts
166.
The Ac servo motors are working on the principle of a. Induction motor b. Synchronous motor c. Dc motor d. Transformer
167.
The servo motors are a. Able to reverse directions quickly b. Not able to accelerate quickly c. Not able to decelerate quickly d. Over heat at stand still
168.
The control winding in case of AC servo motor is excited by a. Variable voltage b. Fixed voltage c. High voltage d. Low voltage
169.
In case of AC servo motor the phase angle between the voltage applied to control winding and voltage applied to the reference winding is a. 900 b. 180 0 c. 270 0 d. 360 0
ET - 2nd MID -
-
170.
The Ac servo motor does a. Not require brushes and slip rings b. Require brushes and slip rings c. Not require main winding d. Require control winding only
171.
The main function of damping torque in an indicating measuring instrument is a. To bring the pointer to rest quickly b. To make pointer move quickly c. To slow down the movement of pointer d. To keeps on moving the pointer
172.
In a. b. c. d.
case of recording instruments the drum rotates Very slowly perpendicular to the direction of pointer Very fastly perpendicular to the direction of pointer Very slowly along the direction of pointer Very fastly along the direction of pointer
173.
If a. b. c. d.
there is no controlling torque the pointer Deflects continuously with out stoppage deflects continuously with stoppage Does not deflect Deflects in stepped manner
174.
The integrating instruments consists of a. Registering mechanism b. Pointer c. Inked pointer d. Graph sheet
175.
The essential requirements of measuring instruments are a. Controlling, deflecting and damping torques b. Controlling and deflecting torques c. Deflecting and damping torques d. Breaking torque
176.
The absolute instruments are also called as a. Standard instruments b. Substandard instruments c. Commercial instruments d. Secondary instruments
177.
Tangent galvanometer is a a. Absolute instrument b. Secondary instrument c. Substandard instrument d. Commercial instrument
178.
The standard instruments are used to a. Calibrate secondary instruments b. Calibrate absolute instruments c. Calibrate angle of deflection d. Calibrate number of turns
179.
The secondary instruments are also called as a. Substandard instruments b. Standard instruments c. Absolute instruments d. Tangent galvano meter
180.
The instruments which indicate the values at that instant are called a. Indicating instruments b. Integrating instruments c. Recording instruments d. Absolute instruments
181.
In moving coil type an iron core is placed in the air gap of the coil to a. Increase flux density b. Decrease flux density
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c. d.
-
Increase current density Decrease current density
182.
The moving coil instruments possess a. High torque and weight ratio b. Low torque and weight ratio c. High weight and torque ratio d. Low weight and torque ratio
183.
In a. b. c. d.
184.
The dynamometer type of moving coil instruments are used for a. Both Ac and Dc measurements b. Ac measurements c. Dc measurements d. Steady state measurements
185.
The moving coil instruments have a. No hysterisis loss b. No eddy current loss c. No mechanical loss d. No copper loss
186.
In a. b. c. d.
moving coil instruments the control torque in produced by Hair springs Eddy currents Iron core magnets Air gap
187.
In a. b. c. d.
moving coil instruments the damping torque is produced by Eddy currents Hair springs Iron core Air gap
188.
In a. b. c. d.
moving coil instruments the deflecting torque is proportional to current proportional to voltage proportional to energy proportional to flux density
189.
The moving coil instruments can not be used for a. Ac measurements b. Dc measurements c. Both Ac and Dc measurements d. steady state measurements
190.
The following instruments have uniform scale a. Moving coil b. Moving iron c. Attraction type moving iron d. Repulsion type moving iron
191.
In a. b. c. d.
moving iron instruments the readings are higher for descending values is mainly due to Hysterisis loss Stray fields Copper loss Eddy current loss
192.
In a. b. c. d.
moving iron instruments the readings are lower for ascending values is mainly due to Hysterisis loss Stray fields Copper loss Eddy current loss
moving coil instruments the deflecting torque is Hair springs Eddy currents Iron core air gap
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-
193.
In a. b. c. d.
case of moving iron instruments the defecting torque is Proportional to square of the current Proportional to the current Inversely to the square of the current Inversely to the current
194.
In a. b. c. d.
case of moving iron instruments the controlling torque is Proportional to Sinθ Proportional to Cosθ Inversely to Sinθ Inversely to Cosθ
195.
In a. b. c. d.
moving iron instruments changes of frequency produce Change in eddy currents Change in hysterisis currents Change in load currents Change in magnetic currents
196.
In a. b. c. d.
case of moving iron instruments scale is not uniform Scale is uniform Scale is zig - zag Scale is circular
197.
In a. b. c. d.
case of moving iron instruments Soft iron moves in the magnetic field Coil moves in the magnetic field Soft iron moves in the electric field Coil moves in the electric field
198.
The power consumption is higher in a. Moving iron instruments b. Moving coil instruments c. Electro - magnetic instruments d. Dynamometer instruments
199.
The moving iron instruments can be used to a. Both DC and AC measurements b. AC measurements only c. DC measurements d. Flow measurements only.
200.
In a. b. c. d.
moving iron instruments the changes of frequency produce Change in impedance of the coil Change in resistance of the coil Change in conductance of the coil Change in resonance frequency of the coil
-
JNTU ONLINE EXAMINATIONS [Mid 2 - ET]
1.
Which of the following determines the direction of the induced emf in the stator just before it begins rotate? a. Fleming's right hand rule b. Kirchoff's law c. Lenz's law d. Ohm's law
2.
The rotating field caused by the stator current induces EMF in the rotor by a. Transformer action b. DC machine action c. Synchronous machine action d. AC machine action
3.
Induction motor works on the principle of a. Mutual induction b. Ampere's law c. Lenz's law d. Ohm's law
4.
The magnitude of rotating magnetic field is equals to a. 1.5 X maximum flux density b. 3X maximum flux density c. 2 X maximum flux density d. Maximum flux density
5.
The rotor speed of induction motor is always slightly a. Less than synchronous speed b. More than synchronous speed c. Less than slip speed d. More than slip speed
6.
The operating speed of induction motor never be equal to a. Synchronous speed b. Slip speed c. Stator speed d. Speed of magnetic field
7.
The induction motor draws balanced three phase current, when it is connected across a a. Balanced three phase ac supply b. Balanced single phase ac supply c. Balanced three phase dc supply d. Balanced dc supply
8.
The direction of rotation of rotating magnetic field gets reversed, when a. Interchanging any two terminals of stator windings b. Interchanging any three terminals of stator windings c. Interchanging any two terminals of rotor windings d. Applying supply voltage to rotor windings
9.
The magnitude of rotating magnetic field is a. Constant b. Not constant c. Varying d. Rotating
10.
An a. b. c. d.
Induction motor is Self-starting with low torque Self-starting with zero torque Self-starting with high torque Non- Self starting
11.
The skewed at a desired angle of the rotor slots in squirrel cage induction motor results a. uniform torque and avoid magnetic locking b. non uniform torque and avoid magnetic locking c. uniform torque and magnetic locking
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d.
-
non uniform torque and magnetic locking
12.
The skewed at a desired angle of the rotor slots in squirrel cage induction motor results a. Reduce humming noise b. increase humming noise c. Non uniform torque d. un avoid magnetic locking
13.
The coil wound rotor must be wound for the same number of poles as that of a. stator b. rotor c. armature d. field
14.
The rotor winding of a squirrel cage induction motor is a. solid un insulated conductors b. similar to the stator winding c. solid insulated conductors d. laminated base conductors
15.
The starting torque of three-phase slip ring induction motor is high because a. Rotor is phase wound b. Rotor resistance is low c. Rotor resistance is zero d. Rotor has short - circuited
16.
The number of slip rings on a squirrel cage induction motor is usually a. Zero b. Two c. Three d. Four
17.
The windings of wound rotors are similar to a. stator windings b. rotor windings c. armature winding d. field winding
18.
The rotor of the squirrel cage induction motor is also called a. Short circuited rotor b. Open circuited rotor c. Open ended rotor d. Stationary rotor
19.
In a. b. c. d.
20.
The three phase winding on the rotor of slip ring induction motor is connected in a. Star b. Delta c. Series d. Parallel
21.
The speed near to the synchronous speed the torque-speed and torque-slip curves are approximately a. Straight line b. Parabola c. Hyperbola d. A curve
22.
The maximum torque in an induction motor depends on a. Square of the supply voltage, frequency, rotor reactance b. Square of the supply current, frequency, rotor reactance c. Square of the supply voltage, frequency, rotor resistance d. Square of the supply current, rotor reactance
a squirrel cage induction motor, the stationary current is 5 to 7 times the rated current Equal to the rated current Double the rated current Half the rated current
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23.
For a slip greater than 0.1 Pu, torque T varies inversely as a. slip b. rotor resistance c. stator resistance d. rotor reactance
24.
The maximum running torque is a. Independent of rotor resistance b. Dependent of rotor resistance c. Dependent on slip d. Independent of rotor frequency
25.
The maximum torque is also called a. Pull-out torque b. Starting torque c. Running torque d. Stator torque
26.
In a. b. c. d.
27.
The torque T developed by induction motor is directly proportional to a. slip, for lower values of S b. slip for higher values of S c. rotor resistance d. stator resistance
28.
The condition for the maximum torque occurs when the slip is equal to a. ratio of rotor resistance and leakage reactance b. ratio of leakage reactance to rotor reactance c. rotor resistance d. leakage reactance
29.
The torque is zero, when a. Slip is zero b. Slip is unity c. Slip is infinity d. Slip is 0.5
30.
The value of the maximum torque is independent of a. rotor resistance b. stator resistance c. rotor reactance d. leakage reactance
31.
The power developed at the shaft is equal to a. Difference of gross mechanical power and mechanical losses b. Difference of input power and output power c. Difference of input power and mechanical power d. Difference of input power and mechanical losses
32.
A 420v, 50Hz, 6-pole, 3- phase induction motor has rotor power input of 80kw. The slip is 3.3 %, then the mechanical power developed is a. 77.33kw b. 154.66kw c. 2.64kw d. 26.4kw
33.
The power input to a 6-pole, 3-Ø, 50Hz induction motor is 40kw. Stator loss is 11kw, and the slip is 45. Then the rotor copper losses are a. 1.56kw b. 1.6kw c. 15.6kw d. 16kw
34.
The rotor core loss is negligible, because
case of induction motor the torque is Directly proportional to slip Inversely proportional to slip Directly proportional to square of the slip Inversely proportional to square of the slip
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a. b. c. d.
-
The frequency of rotor current is small under running conditions The frequency of rotor current is high under running conditions The frequency of stator current is small under running conditions The frequency of stator current is high under running conditions
35.
The power factor of three - phase induction motor at no - load is a. 0.1 b. 0.5 c. 0.6 d. Unity
36.
In a. b. c. d.
37.
The slip of the induction motor is also defined as the ratio of a. Rotor copper loss to rotor input b. Rotor input to rotor copper loss c. Air gap power to rotor input d. Stator copper loss to rotor input
38.
The fractional slip of an induction motor is the ratio of a. Rotor copper loss to rotor input b. Stator copper loss to stator input c. Rotor copper loss to rotor output d. Rotor copper loss to stator copper loss
39.
The input power to the rotor is usually called a. Air gap power b. input power c. out put power d. mechanical power
40.
In a. b. c. d.
41.
In case of star- delta starter, the voltage applied across the winding is a. 1/ times the line voltage
an induction motor the core losses occur mainly in Stator core Armature core Slip rings Brushes
induction motor, the maximum efficiency occurs, when Variable losses equal to constant losses Variable losses are equal to zero Constant losses are equal to zero The total losses equal to zero
b. c. d. 42.
times the line voltage 3 times the line voltage 1/3 times the line voltage
In case of star- delta starter, the starting torque is a. 1/3 times the full-load torque b. 1/ times the full-load torque c. d.
3 times the full-load torque
43.
In a. b. c. d.
case of induction motor, the starting current drawn from the supply is about Four to seven times the full-load current Ten to twelve times the full load current Four to seven times the no load current Ten to twelve times the no load current
44.
In case of auto transformer starting transformation ratio K=1/
times the full-load torque
starting method corresponds to a. Star-delta starting b. DOL starting c. Resistance starter d. Rotor resistance starter 45.
The rotor resistance starter reduces
, this
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a. b. c. d.
-
The magnitude of starting current The magnitude of applied voltage The magnitude of starting speed The magnitude of starting torque
46.
The induction motor is a a. Self starting motor b. Not self starting motor c. Coupled to other drive d. Coupled to other drive
47.
The Rotor resistance starter improves the a. Starting power factor b. Starting current c. Starting voltage d. Starting resistance
48.
The three-phase induction motors up to 5hp can be started by a. Direct on line starter b. Star-delta starter c. Auto transformer starter d. Resistance starter
49.
The star- delta starter is used for a. Squirrel-case Induction motor b. Slip-ring Induction motor c. Phase-wound Induction motor d. Double cage Induction motor
50.
n an squirrel cage induction motor, the starting torque is very low because a. The rotor resistance is small b. The rotor reactance is small c. The rotor resistance is high d. The rotor reactance is high
51.
The salient pole construction is employed for synchronous machines having a comparatively a. Low output and slow speeds b. Large output and slow speeds c. Low output and high speeds d. Large output and high speeds
52.
Three-phase alternators are usually star connected a. To save on copper b. To reduce windage losses c. To reduce conductor size d. To obtain higher terminal voltage
53.
The stator of alternator is made of high permeability laminated steel stampings in order to reduce a. Hysterisis and eddy current losses b. Copper losses c. Mechanical losses d. Friction and wind age losses
54.
The salient type rotor is also called a. Projected type b. Cylindrical type c. Conical type d. Spherical
55.
The function of the winding on the rotor of an alternator is a. To produce flux in the air gap b. To produce torque in the air gap c. To produce induced EMF in the air gap d. To produce current in the air gap
56.
The non-salient type rotor is also called a. Cylindrical type b. Projected type c. Conical type
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d.
-
Spherical type
57.
The rotor of alternator is constructed from laminated high permeability steel in order to reduce a. Eddy-current losses b. Hysterisis losses c. Copper losses d. Friction and wind age losses
58.
The coupling between the electric and mechanical systems is through the medium of a. Electromagnetic field b. Electric field c. Mechanical field d. Electrostatic field
59.
In a. b. c. d.
60.
The speed of a 4-pole 60Hz synchronous machine will be a. 1800rpm b. 1500rpm c. 3000rpm d. 3600rpm
61.
The number of cycles of the induced EMF depends on a. The number of poles b. Number of conductors c. Number of slots d. Number of rotations
62.
The integral number of slots per pole is often used in order to eliminate a. Harmonics in the wave form b. Copper loss c. Core loss d. Friction and wind age loss
63.
An a. b. c. d.
64.
Synchronous generators are used to generate a. Only alternating current b. Only direct current c. Both alternating and direct current d. Either alternating and direct current
65.
The EMF generated in an alternator is a. Average value b. Maximum value c. RMS value d. Virtual value
66.
In a. b. c. d.
67.
EMF generated in an alternator depends upon a. Flux per pole, no. of conductors b. Slip and no. of conductors c. Slip and rated speed d. Flux per mole and rated speed
68.
a rotary machine the purpose of an air gap is to Reduce the mmf required Provide a path for the flux Allow for rotation of the rotor Improve the reluctance
exciter is nothing but a DC shunt generator DC series motor DC shunt motor DC series generator
a Non-salient pole machine The rotor is cylindrical and air gap is uniform The rotor is cylindrical and air gap is non-uniform The rotor is Non-cylindrical and air gap is uniform The rotor is Non-cylindrical and air gap is non-uniform
In an alternator
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a. b. c. d.
-
The conductors are stationary and field is rotating The conductors are rotating and field is also rotating The conductors are stationary and field is also stationary The conductors are rotating and field is stationary
69.
The alternators work on the principle of a. Electromagnetic induction b. Electrostatic induction c. Lenz's law d. Ampere's law
70.
Alternator will convert a. Mechanical energy into electrical energy b. Electrical energy into Mechanical energy c. Mechanical energy into rotating energy d. Mechanical energy into heat energy
71.
Turbo-alternators are generally used to turn at a. 3000rpm b. 1500rpm c. 5000rpm d. 15000rpm
72.
The open type of slots are preferable for use in alternators because a. They easily accommodate the winding b. Their use is less costlier c. They provide wave form d. Their use gives uniform flux distribution
73.
The salient pole type of alternator is also called a. Projected pole type b. Non-salient type c. Cylindrical type d. Un projected type
74.
Salient pole alternators are generally used on a. Low and medium speed prime movers b. Low voltage alternators c. Hydrogen cooled prime movers d. High speed prime movers
75.
In a. b. c. d.
76.
The cylindrical type of alternator is also called a. Non-salient type b. Salient type c. Projected pole type d. Un projected type
77.
Salient pole alternations are used, when a. The speed of the alternator is low b. The power required is large c. The speed of the alternator is high d. The voltage to be generated is high
78.
The advantage of cylindrical type rotor of an alternator is a. Low wind age losses and better balance b. Low copper losses and better balance c. Smooth operation and low core losses d. Less air friction and low variable losses
79.
The rotor preferred for alternators applied to hydraulic turbines are a. Salient pole type b. Cylindrical pole type c. Solid rotor type
a Non-Salient pole machine, the rotor is Cylindrical and air gap is uniform Cylindrical and air gap is non-uniform Non-Cylindrical and air gap is uniform Non-Cylindrical and air gap is non-uniform
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d.
-
Non-salient type
80.
The cylindrical rotor machines have always a. Horizontal configuration b. Vertical configuration c. Both Horizontal and Vertical configurations d. Either Horizontal or Vertical configurations
81.
In a. b. c. d.
which coil the harmonic component of the generated EMF will be more? Full pitch coil Short pitch coil Long pitch coil Same in all coil
82.
In a. b. c. d.
an alternator, if the air gap flux density is non-sinusoidal, then the EMF generated contains Harmonics Composite wave form of voltage and current Only current wave form Only voltage wave form
83.
By to a. b. c. d.
distributing the winding of an alternator into number of slots, the generated EMF can be made
84.
In a. b. c. d.
an alternator the resultant EMF per turn will be Twice the EMF induced in a conductor Equals the EMF induced in a conductor Half the EMF induced in a conductor Thrice the EMF induced in a conductor
85.
To a. b. c. d.
generate sinusoidal EMF's, the special flux distribution in the air gap must be sinusoidal Rectangular Triangular Elliptical
86.
In a. b. c. d.
an alternator the average EMF per phase is equal to 4.44 f Ø T volts 4.44 B T volts 4.44 f B volts 4.44 f T
87.
The EMF equation of an alternator( if the winding for each phase under each pole is distributed) is a. 4.44 f Ø T kc k d volts b. c. d.
Reduce Increase No change Reduce or increase
4.44 f Ø T volts 4.44 f Ø T k c volts 4.44 f Ø T kd volts
88.
A 4 pole, 1500rpm alternator will generate EMF at the frequency of a. 50 Hz b. 60 Hz c. 40 Hz d. 25 Hz
89.
If a. b. c. d.
the speed of alternator is increased the EMF generated will Increase Decrease Remains same No change
90.
In a. b. c.
an alternator, the EMF generated is due to Rate of change flux linkages Transformer action Relative motion between conductors and the field
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d.
-
Electro static induction
91.
The pitch factor is defined as the ratio of the voltage generated in a a. Short pitch coil to the voltage generated in a full pitch coil b. Long pitch coil to the voltage generated in a full pitch coil c. Short pitch coil to the voltage generated half pitch coil d. Long pitch coil to the voltage generated half pitch coil
92.
The advantage of a full-pitched coil span is that it provides a. Higher generated EMF b. Lower armature current c. Lower terminal current d. Higher full-load current
93.
The winding factor is equal to a. Product of distribution and power factors b. Ratio of distribution and power factors c. Ratio of power and distribution factors d. Sum of distribution and power factors
94.
The coil span is defined as a. The separation between coil sides of the same coil b. Separation between two consecutive coils c. Separation between coil ends of the same coil d. Separation between coil ends of different coils
95.
For short pitch and distributed winding, coil span factor and distribution factor are always a. Less than unity b. Greater than unity c. Equals to unity d. Equals to zero
96.
The short-pitched coil means a. The coil span is less than full pitch b. The coil span is less than half pitch c. The coil span is less than quarter pitch d. The coil span is equal to full pitch
97.
Short-pitched coils are employed to a. Save conductor material and reduce high frequency harmonic content b. Save conductor material and increase high frequency harmonic content c. Increase overhang d. Improve the wave form of the generated phase voltage
98.
The voltage generated in a full pitch coil is equal to a. Twice the coil side voltage b. Thrice the coil side voltage c. Coil side voltage d. Half the coil side voltage
99.
The breadth factor is also named as a. Distribution factor b. Pitch factor c. Power factor d. Loss factor
100.
The distribution factor is always a. Less than unity b. Greater than unity c. Equals to unity d. Equals to zero
101.
In a. b. c. d.
102.
In case of synchronous impedance method the synchronous impedance determined at short
synchronous impedance method, the armature reaction effect is replaced by Equivalent voltage drop Equivalent mmf Equivalent reactance drop Equivalent resistance drop
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-
circuit condition is too large due to a. Low degree of saturation b. High degree of saturation c. Medium degree of saturation d. No saturation 103.
The synchronous impedance method can be used for a. Very high capacity alternators b. High capacity alternators c. Low capacity alternators d. Medium capacity alternators
104.
The synchronous reactance of an alternator a. Equivalent reactance representing the armature reaction and leakage reactance b. A false reactance c. A reactance which is fictitious d. Equivalent leakage reactance
105.
The regulation obtained by synchronous impedance method is generally a. Higher than the actual value b. Lower than the actual value c. Equal to actual value d. equal to zero
106.
The synchronous impedance method is used to determine a. Regulation of cylindrical rotor synchronous machine b. Regulation of salient pole synchronous machine c. Regulation of projected type synchronous machine d. Regulation of DC machine
107.
The synchronous impedance method is a. Pessimistic method b. Optimistic method c. Equality method d. Used for salient pole machines
108.
The synchronous impedance method is also called a. EMF method b. Ampere method c. MMF method d. Zero power factor method
109.
When there is no saturation, the synchronous impedance is a. Constant b. Reduces c. Increases d. Varies
110.
The synchronous impedance varies with a. Load and power factor conditions b. Only load conditions c. Only power factor conditions d. Terminal voltage conditions
111.
The open circuit characteristics of an alternator resembles a. B-H curve of magnetic material b. B-H curve of insulating material c. Speed torque characteristics of DC motor d. Load characteristics of DC generator
112.
The following test results are not affected by the variation in the speed of an alternator a. Short circuit test b. Open circuit test c. Short circuit and Open circuit tests d. Synchronous impedance method
113.
The synchronous impedance of an alternator is high at a. Lower excitations b. Higher excitations
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c. d.
-
Zero excitation Very high excitations
114.
The synchronous impedance of an alternator is low at a. Higher excitations b. Lower excitations c. Zero excitation d. Very low excitations
115.
The regulation of an alternator can be predetermined by conducting a. Open circuit and short circuit tests b. Open circuit test only c. Short circuit test only d. Load test
116.
The open circuit and short circuit tests are performed on a three-phase generator to determine a. Synchronous reactance b. Synchronous resistance c. Field resistance d. Field reactance
117.
The open circuit characteristic is plotted with a. Field current Vs phase voltage b. Field current Vs Line voltage c. Field current Vs phase current d. Field current Vs line current
118.
The short circuit characteristics of an alternator is a a. Straight line b. Parabola c. Hyperbola d. Semi-circle
119.
The magnetization characteristic of the generator is also called as a. Open circuit characteristics b. Short circuit characteristics c. Load characteristics d. Starting characteristics
120.
The short circuit ratio is a. Inversely proportional to the synchronous reactance b. Directly proportional to the synchronous reactance c. Inversely proportional to the synchronous resistance d. Directly proportional to the synchronous resistance
121.
The single-phase induction motors are not self-starting, because a. There is no relative motion between the stator and motor magnetic fields b. The magnitude of the flux produced in stator is low c. No voltage is induced in the rotor circuit d. Zero magnetic flux in rotor
122.
In a. b. c. d.
123.
The backward rotor slip in an induction motor is equal to a. (2-S) b. (1-S) c. S d. (S-1)
124.
In a. b. c. d.
case of double revolving field theory, a field can be resolved into two equal fields Rotating in opposite directions with equal angular velocities Rotating in same directions with equal angular velocities Rotating in opposite directions with unequal angular velocities Rotating in same directions with unequal angular velocities
case of single coil carrying an alternating current, the flux in air gap is Pulsating Rotating Constant Revolving
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-
125.
Single phase induction motor has no self- starting because a. The transformer EMF is induced in the rotor at stand still producing zero net torque b. Stator flux is pulsating c. No revolving field in the rotor d. No EMF induced in the motor
126.
The starting characteristics of single phase induction motors are described qualitatively by a. Double revolving field theory b. Rotating field theory c. Static field theory d. Magnetic field theory
127.
In case of single phase induction motor the torque produced by the forward and backward fields are a. Equal and opposite b. Equal c. Unequal and opposite d. Unequal
128.
The speed of rotation of the two magnetic fields is a. 120 f/p b. 240f/p c. 120p/f d. 240 p/f
129.
The torque developed by a single phase motor at starting is a. Zero b. More than the rated torque c. Less than the rated torque d. Rated torque
130.
The single-phase induction motor operate at a. Low power factor b. High power factor c. Unity power factor d. Medium power factor
131.
The single phase induction motor used in ceiling fan and table fan is a. Capacitor start and run motor b. Capacitor start motor c. Capacitor run motor d. Split phase motor
132.
If a. b. c. d.
133.
The capacitor start motors produce a. Very high starting torque b. Low starting torque c. Minimum starting torque d. Starting torque is zero
134.
In a. b. c. d.
135.
The capacitor in the starting winding of the single phase induction motor improves a. The power factor b. The starting current c. The starting voltage d. The starting reactance
136.
The main advantages of a capacitor run motor is a. It not only provides starting torque and also improves the power factor
the capacitor of a single phase motor is short circuited The motor will not start The motor will burn The motor will run in reverse direction The motor will run in the same direction at reduced rpm
case of capacitor start and capacitor run motors Capacitor remains in the circuit permanently Capacitor remains in the circuit temporarily Inductor remains in the auxiliary winding Resistor remains in the auxiliary winding
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-
b. c. d.
It is cheap It provides the starting torque It is easy to manufacture
137.
In a. b. c. d.
case of capacitor start single phase induction motor A capacitor of high value is only used for starting A capacitor of low value is only used for starting A capacitor of high value is only used for improving power factor A capacitor of low value is only used for improving power factor
138.
The stator winding of single phase induction motor is also called a. Main winding b. Auxiliary winding c. Starting winding d. Rotor winding
139.
The auxiliary winding of single phase induction motor is also called a. Starting winding b. Main winding c. Rotor winding d. Stator winding
140.
In case of capacitor start induction motors the phase difference between main current and starting current a. Almost 900 b. Less than 600 c. Equal to zero d. Between 200 to 40 0
141.
The A.C. servo motor is basically a. Two-phase induction motor b. Single phase induction motor c. Three phase induction motor d. DC motor
142.
In a. b. c. d.
143.
The main difference between a control transmitter (CX) and a control transformer (CT) is a. Electrical angle is different in addition to the air gap being uniform b. Air gap is less in the case of CT c. Air gap is more or less uniform in the case of a CT d. Electrical angle is different
144.
Permanent magnet tachometers are a. Compact, efficient and reliable b. Bulky, efficient and reliable c. Compact, low efficient and reliable d. Compact, efficient and non-reliable
145.
In a. b. c. d.
DC Tachometer, the high inertia of the rotor can be reduced by Iron less rotor Iron rotors Iron less stator Iron stator
146.
AC a. b. c. d.
serve motors are best suited for Low power applications High power applications Medium power applications Very high power applications
147.
Servo motors work on the principle of a. Transformer b. An induction motor
case of photo electric tachometer the number of pulses generated depends up on The number of holes in the disc and speed The speed only The applied voltage The input power
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-
c. d.
Lenz's law Ampere's circuit law
148.
In a. b. c. d.
servo system the output is A mechanical variable, like position, velocity or acceleration An electrical variable, like voltage, current or power An electrical variable, like, charge, flux or resistance A mechanical variable, like length, time or precision
149.
Ac a. b. c. d.
servo motors are not suited for High power applications Low power applications Very low power applications Medium low power applications
150.
An electro mechanical unit which generates an electrical output proportional to the speed of the shaft is called a. Tachometer b. Servo motor c. Synchro d. Single phase commutator motor
151.
A machine has a distributed 3-phase winding on stator and a Two-pole single phase winding on rotor is called a. Synchro b. Ac servo motor c. Dc motor d. Induction motor
152.
The holding torque of the stepper motor a. Increases with the exciting current b. Decreases with the exciting current c. Increases with the speed d. Decreases with the voltage
153.
The synchros are a. Self - Synchronizing machines b. Dc machines c. Induction machines d. Static machines
154.
The motor used in computer printers is a. Stepper motor b. Dc shunt motor c. Dc series motor d. Induction motor
155.
The motors used for adding and subtracting rotary speeds are a. Synchros b. Tacho generators c. Dc motors d. Ac motors
156.
A stepper motor a. Does not rotate continuously b. Does rotate continuously c. Runs at very high speeds d. Runs at very low speeds
157.
The following motor is an incremental motion motor a. Stepper motor b. Induction motor c. Dc motor d. Ac motor
158.
The stepper motor is a special type of a. Synchronous motor b. Dc motor c. Hysterisis motor
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d.
-
Repulsion motor
159.
A synchro is a. Miniature Dc machine b. Miniature Ac static machine c. Miniature Ac induction machine d. Miniature Ac Dynamic
160.
The synchros are used for a. Error detection b. servo mechanism for voltage Transmission c. Rotating speeds d. current detection
161.
The frequency of two phase AC servo motors varies from a. 50 Hz to 400 Hz b. 1 Hz to 50 Hz c. 400 Hz to 700 Hz d. 700 Hz to 1000 Hz
162.
The following motor have the slope of Torque- Speed characteristic is negative a. Ac servo motor b. Dc motor c. Induction motor d. Synchronous motor
163.
The servo motor has characteristic of a. High torque at all speeds including zero speed b. low torque at all speeds including zero speed c. Medium torque at all speeds including zero speed d. No torque at all speeds including zero speed
164.
The torque- speed characteristic of Ac servo motor is a. Linear b. Non- Linear c. Parabolic d. Hyperbola
165.
The servo motors consume power from a. A fraction of watt up to a few 100watts b. A fraction of watt up to a 1 watt c. 1000 watts to 1 mega watt d. 100 watts to 1000walts
166.
The Ac servo motors are working on the principle of a. Induction motor b. Synchronous motor c. Dc motor d. Transformer
167.
The servo motors are a. Able to reverse directions quickly b. Not able to accelerate quickly c. Not able to decelerate quickly d. Over heat at stand still
168.
The control winding in case of AC servo motor is excited by a. Variable voltage b. Fixed voltage c. High voltage d. Low voltage
169.
In case of AC servo motor the phase angle between the voltage applied to control winding and voltage applied to the reference winding is a. 900 b. 180 0 c. 270 0 d. 360 0
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-
170.
The Ac servo motor does a. Not require brushes and slip rings b. Require brushes and slip rings c. Not require main winding d. Require control winding only
171.
The main function of damping torque in an indicating measuring instrument is a. To bring the pointer to rest quickly b. To make pointer move quickly c. To slow down the movement of pointer d. To keeps on moving the pointer
172.
In a. b. c. d.
case of recording instruments the drum rotates Very slowly perpendicular to the direction of pointer Very fastly perpendicular to the direction of pointer Very slowly along the direction of pointer Very fastly along the direction of pointer
173.
If a. b. c. d.
there is no controlling torque the pointer Deflects continuously with out stoppage deflects continuously with stoppage Does not deflect Deflects in stepped manner
174.
The integrating instruments consists of a. Registering mechanism b. Pointer c. Inked pointer d. Graph sheet
175.
The essential requirements of measuring instruments are a. Controlling, deflecting and damping torques b. Controlling and deflecting torques c. Deflecting and damping torques d. Breaking torque
176.
The absolute instruments are also called as a. Standard instruments b. Substandard instruments c. Commercial instruments d. Secondary instruments
177.
Tangent galvanometer is a a. Absolute instrument b. Secondary instrument c. Substandard instrument d. Commercial instrument
178.
The standard instruments are used to a. Calibrate secondary instruments b. Calibrate absolute instruments c. Calibrate angle of deflection d. Calibrate number of turns
179.
The secondary instruments are also called as a. Substandard instruments b. Standard instruments c. Absolute instruments d. Tangent galvano meter
180.
The instruments which indicate the values at that instant are called a. Indicating instruments b. Integrating instruments c. Recording instruments d. Absolute instruments
181.
In moving coil type an iron core is placed in the air gap of the coil to a. Increase flux density b. Decrease flux density
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c. d.
-
Increase current density Decrease current density
182.
The moving coil instruments possess a. High torque and weight ratio b. Low torque and weight ratio c. High weight and torque ratio d. Low weight and torque ratio
183.
In a. b. c. d.
184.
The dynamometer type of moving coil instruments are used for a. Both Ac and Dc measurements b. Ac measurements c. Dc measurements d. Steady state measurements
185.
The moving coil instruments have a. No hysterisis loss b. No eddy current loss c. No mechanical loss d. No copper loss
186.
In a. b. c. d.
moving coil instruments the control torque in produced by Hair springs Eddy currents Iron core magnets Air gap
187.
In a. b. c. d.
moving coil instruments the damping torque is produced by Eddy currents Hair springs Iron core Air gap
188.
In a. b. c. d.
moving coil instruments the deflecting torque is proportional to current proportional to voltage proportional to energy proportional to flux density
189.
The moving coil instruments can not be used for a. Ac measurements b. Dc measurements c. Both Ac and Dc measurements d. steady state measurements
190.
The following instruments have uniform scale a. Moving coil b. Moving iron c. Attraction type moving iron d. Repulsion type moving iron
191.
In a. b. c. d.
moving iron instruments the readings are higher for descending values is mainly due to Hysterisis loss Stray fields Copper loss Eddy current loss
192.
In a. b. c. d.
moving iron instruments the readings are lower for ascending values is mainly due to Hysterisis loss Stray fields Copper loss Eddy current loss
moving coil instruments the deflecting torque is Hair springs Eddy currents Iron core air gap
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-
193.
In a. b. c. d.
case of moving iron instruments the defecting torque is Proportional to square of the current Proportional to the current Inversely to the square of the current Inversely to the current
194.
In a. b. c. d.
case of moving iron instruments the controlling torque is Proportional to Sinθ Proportional to Cosθ Inversely to Sinθ Inversely to Cosθ
195.
In a. b. c. d.
moving iron instruments changes of frequency produce Change in eddy currents Change in hysterisis currents Change in load currents Change in magnetic currents
196.
In a. b. c. d.
case of moving iron instruments scale is not uniform Scale is uniform Scale is zig - zag Scale is circular
197.
In a. b. c. d.
case of moving iron instruments Soft iron moves in the magnetic field Coil moves in the magnetic field Soft iron moves in the electric field Coil moves in the electric field
198.
The power consumption is higher in a. Moving iron instruments b. Moving coil instruments c. Electro - magnetic instruments d. Dynamometer instruments
199.
The moving iron instruments can be used to a. Both DC and AC measurements b. AC measurements only c. DC measurements d. Flow measurements only.
200.
In a. b. c. d.
moving iron instruments the changes of frequency produce Change in impedance of the coil Change in resistance of the coil Change in conductance of the coil Change in resonance frequency of the coil
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