1) What Are The Classifications Of Hazardous Area? Hazardous Area

1) What are the classifications of hazardous area? Hazardous area is one where explosive gas-air mixture is present. Area classification: ZONE 0, ZONE 1, ZONE 2. 2) Where lead covered cables are used? Why PVC cables are not used? Lead covered cables are used the environment will affect the PVC insulation. 3) What is fire alarm? What is smoke detector? Smoke detector detects smoke due to fire. When detector detects smoke fire alarm will come. 4) On what principle does the induction motor work? It works on Faradys laws of electro magnetic induction. 5) What are the protections included to a motor starter? Over load relay and Fuse for backup protection 6) Will a transformer work on D.C supply? No, It will not work on DC. It’s working based on statically induced emf. 7) What are the difference between A.C three phase and single phase motor? Three phase motors are of huge capacity. Single phase motors are smaller capacity 8) What is earthing? what are the different types of earthing? Earthing means connecting equipment to earth potential. a) Solid earthing, b) Resistance earthing, c) Reactence earthing. 9) How to measure the current in a running motor? By clip-on meter, tong tester. 10) Explain the maintenance of a battery cell. Check specific gravity of the cell, electrolyte level, voltage and terminal connection cleanliness. 11) Write the standard lengths of fluorescent tubes. Two feet, four feet, five feet 12) What is ELCB? How is it working? ELCB means earth leakage circuit breaker. It senses the leakage current to earth and trip the circuit. 13) What is the purpose of cable glanding? Earthing and sealing cable ends. 14) Write the standard range of cross section of conductors in the power cable. 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 185, 240, 300, 350, 400, 450, 500, 600. 15) A room circuit breaker trips, wiring found O.K. what will you do to rectify? Check weather the circuit is over loaded. 16) Draw DOL starter diagram and explain? 17)

Draw double tube in parallel connection.

18) What is a timer? Connect a 110V A.C timer across 230V A.C supply. Timer is a device, which delays operation. 19) What is overloading of a motor? Overloading of a motor means loading beyond its full capacity

20) What is transformer oil test? It is a breakdown die electric test. It should withstand 30 KV for 1 minute at gab between two electrode is 2.4 mm 21) Name the parts of motor. Stator, Rotor, windings, frame, bearings and fan. 22) Can we take a power connection from lighting circuit? It depends on capacity available. If the capacity is available, we can take power connection from lighting circuit. 23) How many types of starters are there? Name them. Direct on line starter, auto transformer starter, star delta starter and rotor resistance starter 24) What are the types of lamps available? Pin type and screw type filament lamp (low pressure), metal halide lamp (high pressure) sodium vapor lamp and mercury vapor lamp 25) Draw the diagram of fluorescent tube fitting and explain?

26) What are the types of transformer? Shell type, core type 27) What are the types of relays? Thermal over load relay, electromagnetic relay, gas operated relay and static relay. 28) What are the types of battery? Dry type, lead acid and nickel cadmium. 29) What is UPS? Draw the block diagram and explain? UPS means uninterrupted power supply. It is a combine unit consists of rectifiers, battery, inverter and static bypass switch. When normal power is available, AC is rectified to DC and power is given to inverter as well as will charge the battery. When Ac main fails, battery will supply power to inverter and power will be maintained to the load. 30) Why batteries are connected in series and parallel? When there is need of high DC current, batteries are connected in parallel. When DC voltage is important they will be connected in series. 31) What are the types of motors? AC motor and DC motor. DC motor classified as a) Series motor, b) Shunt motor, c) cumulative compound motor and d) differential compound motor. AC motor classified as single-phase motor and three phase motor. Single-phase motor classified as a) universal motor, b) capacitor start motor. Three phase motor classified as a) asynchronous motor or induction and b) synchronous motor. Induction motor classified as a) squirrel cage motor and b) slip ring motor. 32) What are the common types of cables? a) PVC cable, b) PILC cable and c) XLPE cable.

33) What is specific gravity? How much is the specific gravity of a lead acid cell? What is the instrument used for measuring? Specific gravity is the compound present in a liter of liquid and it is measured in gm/liter. Specific gravity of lead acid cell is 1200 gm/liter. When a cell is fully charged its specific gravity is 1260. and 1160 when the cell is discharged. To measure specific gravity hydrometer is used. 34) How to change the rotation of a motor? To change rotation of motor, interchange any two phase of motor 35) What will be winding resistance of a motor? It will be in ohm. 36) What will you do if a motor is found smoking? First switch off it’s power supply. 37) How to check a capacitor? Using multimeter. First measure resistance of capacitor, then change any one lead and again measure the resistance, the deflection of the pointer should be in two opposite directions. 38) If a motor trips frequently, what can be the reason? a) motor may be over loaded, b) motor connection may be loose and c) over load relay may be faulty. 39) What is I.R value? Explain. I.R value is the insulating resistance of an equipment to electric circuit. It will be measured by megger and it’s valuewill be in M Ohm. 40) Draw the common symbols in a power distribution. 41) What is the procedure for electrical isolation? ℜ•Get the duly signed isolation slip from the concerned production plant and check Tag No. on panel/module and confirm the correctness of isolation. ℜ• Incase of HT equipment, switch off/remove closing supply fuse and rack out the breaker in test position and if necessary apply circuit earth. ℜ• Incase of MCB switch off MCB ℜ• Incase of switch fuse unit switch off supply and remove fuses. ℜ• Lock circuit breaker door, MCB handle, switch handle in out position by padlock ℜ• Sign the isolation slip and put original on the panel and hand over the duplicate slip to the concerned production plant 42) Why do you test the transformer oil? Transformer oil is mineral oil and hygroscopic. If oil absorbs moisture it will lose it’s insulation property. So we should have to ensure that oil does not contain moisture. Oil sample is collected the transformer and tested in oil test kit. It should withstand 30 KV for 1 minute. 43) What is cathodic protection? Corrosion is electrolytic process, where pipe material acts as positively charged electrode and current flows to earth eroding material on the pipe. In cathodic protection system pipe is negatively charged with reference to earth by this we can avoid erosion on the pipe line.

44) What is HI-POT test? This test is carried out on cables, transformers and high-tension motors to confirm its insulation strength. 45) What is work permit? Permits are standardized forms, which need to be filled in and signed by authrirized personnel, before work can commence for the purpose of achieving the following objectives. ℜ• Limit hazards associated with work by planning the activites, providing a reminder of hazards involved and special precautions required to ensure safety. ℜ•Keep records of on going work activities and their work location in case of emergencies. ℜ• Provide a formal agreement between all personnel involved in performing work in the plant. ℜ• To ensure that the job is executed in a safe manner and housekeeping is maintained. ℜ• Type of permits: a) Cold work permit, b) Hot work permit, c) Entry permit, d) Radiography work permit