ETO ETO Exam papers 📅 Nov 2022

Exam Question

(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 0.2 Ω. The machine has six poles and the armature is lap-connected with 864 conductors. The flux per pole is 0.05 Wb. Calculate (10)

(a) The speed;

(b) The gross torque developed by the armature.

Reference Answer

A SCR is a 4-layered PNPN switching solid-state current controlling device. These are unidirectional devices. SCR is triggered by a current going into the gate.
It has three modes of operation:
Forward blocking mode (OFF state)
Forward conducting mode (ON state)

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