DC & AC additional

Objective type:

1. If the exciter switch in the prime mover is in the "ON" position during starting, it will provide power to the exciter, which, in turn, supplies the initial field current to the generator or motor. This is essential for generating the initial magnetic field needed for the generation of electricity or motor operation.

2. When the exciter control knob is varied in a Synchronous Motor, the excitation current to the motor's field winding is adjusted, which can change the motor's speed or power factor, depending on the direction and magnitude of the adjustment.

3. A factor that does not decrease the terminal voltage of a Separately Excited DC Shunt Generator is "Armature resistance." This factor usually has a negligible effect on the terminal voltage.

4. True for a DC Shunt Generator: (i) When the load increases, terminal voltage increases. (ii) When the load increases, armature current increases. (iii) When the load increases, power generated increases.

5. The degree of compounding of a DC Compound Generator is said to be "flat compounded" when the series and shunt field fluxes produce a constant terminal voltage regardless of the load variations.

6. Long-distance transmission of power via cables or bus bars is ideally suited for "over-compounding" of a generator.

7. When the flux created by the series field opposes that of the shunt field, it is called "differential compounding."

True or False:
False. DC motors can have an odd number of poles.

True. DC motors can have an odd number of parallel paths in their armature windings.

False. DC motors can have an odd number of conductors in their armature windings.

False. DC motors are classified as self-excited or separately excited.

True. To change the rotation of a DC motor, you can change the connection of the field or the armature, but not both.

True. The smaller the load of a motor, the smaller its counter EMF (back EMF).

True. In a shunt motor, if the field circuit resistance is not changed, the flux of the motor remains relatively constant.

True In a motor, as the flux increases, the torque typically increases.

False. In a motor, as the flux increases, the speed typically increases.

True. In a DC motor, the speed at full-load is generally less than the speed at no-load.

True. In a DC generator, the counter EMF at standstill is equal to the terminal voltage. If a DC motor has no load, its armature current is zero.

False. For constant speed applications, a lower speed regulation is better.

False. DC motors can be self-excited or separately excited, just like DC generators.

True. If a DC motor has no load, its armature current is very close to zero.

True. For constant speed applications, a lower speed regulation is better.

True. The smaller the armature current in a motor, the smaller the torque produced.

True. The starting current of a motor is typically higher than its running current.

False. In a motor, the starting torque is usually higher than the running torque.

True As the flux increases in a motor, the speed typically decreases.

True. In a motor, the counter EMF may be greater than the terminal voltage.

False. In a motor, the counter EMF is not always less than the terminal voltage.

True. In a motor, the higher the starter resistance, the higher the starting current.

True. As the load of a motor increases, its speed typically decreases.

True. 1 N-m of torque is greater than 1 ft-lb of torque.

True. 1 rps (revolution per second) is the same as 60 rpm (revolutions per minute) of speed.