Quiz

Q1. A 220-V d.c. machine has an armature resistance of 1.0 \(\Omega\). If the full-load armature current is 10 A, find the induced e.m.f. when the machine acts as (a) generator (b) motor. (Assume d.c. machine to be shunt connected and in each case it is considered negligible)

Q2. A 4 pole generator with 16 coils has a two layer lap winding. The pole pitch is

Q3. Identify the equation of synchronous motor when operating in leading power factor.

Q4. An alternator is supplying load of 300 kW at a power factor of 0.5 lagging. If the power factor is raised to unity, how many more kilowatts can alternator supply for the same kVA loading?

Q5. If the transformer is applied rated supply voltage with double frequency, then it's Eddy current losses will be

Q6. A synchronous motor, fed from infinite bus , is working at half load, if increased in it's field current causes a reduction in the armature current, then the motor is

Q7. For a single phase transformer, the maximum efficiency occurs at 75% of the load, then \(\frac{iron\:loss\:at\:full\:load}{copper\:loss\:at\:full\:load}=?\)

Q8. A trasformer at full load has a copper loss of 400 W and an iron loss of 200 W. The copper loss and iron loss at half full load will respectively be

Q9. A 50 kVA, 4400/220 V transformer has primary winding and secondary winding resistance are R1 = 3.45 \(\Omega\) and R2 = 0.009 \(\Omega\) respectively. Calculate the equivalent resistance of the transformer as referred to primary side.

Q10. If the full-load copper loss of a transformer is 800 W, then the copper loss at half-load is__________.