8.a) What is a silicon controlled rectifier (SCR) ? How is the breakover voltage of the SCR defined?
(6)
b) A d.c. motor takes an armature current of 110 A at 480 V. The resistance of the armature circuit is 0.22. The machine has six poles and the armature is lap-connected with 864 conductors. The flux per pole is 0.05 Wb. Calculate
(a) The speed;
(b) The gross torque developed by the armature.(10)
Reference Answer
### Part (a): Silicon Controlled Rectifier (SCR) #### 1. Definition of an SCR A Silicon Controlled Rectifier (SCR) is a three-terminal, four-layer (P-N-P-N) unidirectional semiconductor switching device. It is a type of thyristor, primarily used for controlling high-power AC or DC circuits. * **Terminals**: It has three terminals:
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