Disparo Scr 106.docx

LABORATORY N.2 CONTROL ANGLE OF SHOOTING WITH SCR Agustin castro lopez [email protected] Gabriel Gonzalez [email protected]

For SCRs the device consists of an anode and a cathode, where the joints are of type P-N-P-N between them. Therefore it can be modeled as 2 typical transistors P-N-P and N-P-N, so it is also said that the thyristor works with voltage feedback. 3 joints are thus created (called J1, J2, J3 respectively), the door terminal is

1. OBJECTIVES • Overall objective -

Design and implement a circuit that allows controlling the angle of conduction or firing in a load.

• Specific objectives -

Carry out measurements of and make theoretical comparisons with the practices o Observe and analyze the behavior of said assembly make changes based on the measurements to achieve the objective proposed in class.

connected to junction J2 (NP junction).

Figura 1. Esquema tiristor

1.1 Shooting methods 1. THEORETICAL FRAMEWORK 1.1 Definition The thyristor corresponds to a family of electronic components consisting of semiconductor elements that use internal feedback to produce a switching. The materials of which it is composed are of the semiconductor type, that is to say, depending on the temperature at which they are located they can function as insulators or as conductors. They are unidirectional (SCR) or bidirectional (TRIAC) or (DIAC) devices. It is generally used for the control of electrical power.

For the triggering of a thyristor, the anode - cathode junction must be live polarized and the control signal must remain long enough to allow the thyristor to reach an anode current value greater than IL, the necessary current to allow the SCR to start driving. So that, once fired, it remains in the driving zone, a minimum current of IH value must circulate, marking the passage from the driving state to the direct blocking state. 1.1.1 Shot per door When the anode voltage becomes positive with respect to the cathode,

junctions J1 and J3 have direct or positive polarization. Junction J2 has reverse polarization, and only a small leakage current called idle state current ID will flow. It is then said that the Thyristor is in a direct blocking condition in the deactivated state. If the anode to cathode voltage VAK increases to a sufficiently large value, the reverse polarized J2 junction will break. This is known as avalanche rupture and the corresponding voltage is called the direct breaking voltage VB0. Since the junctions J1 and J3 already have direct polarization, there will be a free movement of carriers through the three junctions, which will cause a large direct current from the anode. It is then said that the device is in a driving or activated state. The above can be better understood when observing the graph of the characteristic curve of the Thyristor, which is shown in the following figure.

2.2.3 Triggering by voltage gradient A sharp rise in the anode potential in the direct direction of conduction causes the trip. This case, rather than a method, is considered an inconvenience.

2.2.4 Radiation firing It is associated with the creation of electron-hole pairs by the absorption of light from the semiconductor element. The light-activated SCR is called LASCR. 2.2.5 Shooting by temperature The temperature trigger is associated with the increase of electron-hole pairs generated in the semiconductor junctions. Thus, the sum of the currents tends rapidly as the temperature increases. The breaking voltage remains constant up to a certain value of the temperature and decreases with increasing temperature.

Figura 2. Curva característica del tiristor Figura 3. Disparos de SCR Effects with inductive loads 2.2.2 Triggering by voltage module It is due to the avalanche multiplication mechanism. This form of trip is not used to intentionally trip the thyristor; however, it happens in a fortuitous way caused by abnormal voltage in the electronic equipment.

When the load of the SCR is an inductive load, (it behaves like an inductor), it is important to take into account the time it takes the current to increase in a coil. The pulse applied to the gate must be durable enough so that the current of the load equals the coupling current and thus the thyristor remains in conduction. In this

type of charge, the current can, in principle, change as suddenly as the voltage does. But if the circuit is inductive, as it is the case of electric motors, then the current can not undergo sudden changes, being able to arrive to have a considerable delay with respect to the tension. If the inductance is high, two problems can appear: It can happen that the thyristor does not even turn on, if it turns out that when the current is very slowly growing at the moment of activation of the gate, when the activation pulse stops, the current has not even reached the minimum IH necessary to keep the thyristor on. The solution to this problem is to make the ignition pulses longer. If the current delay is very large, it may be that when it becomes less than the holding current I_H, the voltage is already so great that the thyristor remains on, so that it never shuts off. To avoid this problem, a diode is mounted in parallel with the load to derive the excess current that causes the thyristor to not clos

Figura 4. Corriente y voltaje con carga inductiva

1. MATHEMATICAL DESIGN AND DEVELOPMENT

In the laboratory there are four assemblies with different types of power and tripping in addition to the variation of the loads between resistive and inductive, that is, there will be eight assemblies based on the four basic ones. Materials used in practice • Tiristor BT151-500R-only for simulation • Thyristor C106D • Capacitors • Reducer Motor • AC motor • DC Bulb • AC bulbs 3.1 Circuit. In order to achieve AC tripping, it must be clear what type of thyristor is to be used since, depending on the model, the values provided in the datasheet by the manufacturer will allow the mathematical development of the components of the tripping circuit, the proposed assembly is the next:

Figura 5. Disparo con fuente AC

For this case the C106D will be used and to corroborate the mathematical development data at the end of this report will be attached its corresponding datasheet. The data are:

𝑉𝑆 = 200𝑉 ; 𝑉𝐺𝑇𝑚𝑖𝑛 = 0.8𝑉 ; 𝐼𝐺𝑇𝑚𝑖𝑛 = 200𝑚𝐴 ; 𝐼𝐺𝑇𝑚𝑎𝑥 = 500𝑚𝐴 ;

1. PHOTOGRAPHIC RECORDS

We assume the value of the capacitor for this ceramic case of C = 100nF code 104. The time constant (R1 + R2) C, must be in the range of 2x 〖10〗 ^ 3 and 30x 〖10 〗 ^ 3 in order to obtain a wide adjustment range, the time constant must be able to be adjusted with a large part of This range, we assimilate the ranges in 2x 〖10〗 ^ 3 and 25x 〖10〗 ^ 3. The minimum constant of tempo occurs when R2 is completely 0, in such a way: (R1+0)(100𝑋10−9)=2𝑋103

We clear and get R1. R1=20k The maximum time constant (maximum firing angle) occurs when R2 is at its maximum value, so we decide that: (R2+20)(100𝑋10−9)=25𝑋103 We clear and obtain the value of the potentiometer for R2. R2=230k

To analyze the assembly of the circuits and their correct operation the teacher in charge requests to take measurements of the currents of enchanche and maintenance of the circuit with its resistive and inductive loads. 2. CONCLUSIONS. - After turning on the scr, it is not necessary that the gate continue receiving power because it will continue to drive until the voltage decreases to such an extent that it is deactivated . - The scr allow us to control the passage of current to certain branches of a circuit preventing damage and extending the life of these. - According to the reference of the scr they can control different types of returns. - As long as no voltage is applied to the GATE of the scr, the conduction does not start, since this is the key for the thyristor to remain active.

1. BIBLIOGRAPHY. https://sensoricx.com/electroni ca-de-potencia/la-guia-maximascr/ http://www.itcelaya.edu.mx/ojs/i ndex.php/pistas/article/downloa d/410/397 https://elsiecasttro.wordpress.c om/2014/11/03/practica-4implementacion-de-metodosde-disparo-de-triacs/