A 150 V, dc. separately excited motor is used to lift material. The motor has an armature resistance of 1 ?, and K? = 3 Vs. The load torque is 9 Nm. The armature voltage of the motor is controlled by a single-phase, full-wave, ac/dc solid-state converter employing SCRs. The voltage on the ac side of the converter is 120 V (rms). The triggering angle of the SCRs is 30o when the motor is lifting up the load. Calculate the motor speed. Also calculate the triggering angle required to lower the same load at the same speed.

Question

What will be an ideal response?

Answer 1

The load is a hoist, hence constant load torque.

Now, assuming constant field, the armature current will be constant.



Assuming continuous current, we have,