Question 1

The rotor is excited by a source of direct current so that it produces simultaneous north and south poles.

Accepted Answer

The statement describes a characteristic of the stator, not the rotor, in the context of synchronous machines. The rotor is typically excited to produce a magnetic field, but the simultaneous north and south poles are a feature of the stator's magnetic field interaction with the rotor in an electric motor or generator.

Question 2

A method for applying excitation current to the rotor is with a exciter.&#10;A)rectifier&#10;B)brushless&#10;C)complementary&#10;D)supplementary

Accepted Answer

A brushless exciter is the best choice as it eliminates the need for brushes and slip rings, increasing reliability and reducing maintenance. A rectifier exciter is a common alternative, but it requires brushes and slip rings to transfer the excitation current to the rotor. Complementary and supplementary exciters are not commonly used for this application. A brushless exciter is a low-maintenance and efficient method for providing excitation current to the rotor. It uses a small amount of the generator's output voltage to generate the necessary DC voltage, eliminating the need for brushes and slip rings. Rectifiers, complementary, and supplementary exciters all require additional components and maintenance compared to a brushless exciter.

Question 3

A synchronous motor converts AC electrical energy into power.&#10;A)thermal&#10;B)hydraulic&#10;C)pneumatic&#10;D)mechanical

Accepted Answer

A synchronous motor converts AC electrical energy into mechanical power, which is used to turn a shaft or rotor. There is no conversion into thermal, hydraulic, or pneumatic power. A synchronous motor converts the AC electrical energy into mechanical power. This mechanical power is used to drive loads such as pumps, fans, compressors, and other mechanical systems.

Question 4

An advantage of the synchronous motor equipped with a brushless exciter is that .&#10;A)field control and excitation are provided by a static system&#10;B)brush sparking is produced&#10;C)field excitation is manually removed whenever the motor is out of step&#10;D)manual resynchronization can be achieved whenever it is practical

Accepted Answer

The synchronous motor equipped with a brushless exciter provides field control and excitation through a static system, which eliminates the need for brushes and reduces maintenance requirements. It also allows for automatic synchronization, as the excitation can be adjusted in real-time to maintain the proper speed and power factor. Options B, C, and D are incorrect as they describe disadvantages or limitations of the synchronous motor system. The synchronous motor equipped with a brushless exciter has the advantage of providing field control and excitation through a static system, eliminating the need for brushes that can produce sparking. Additionally, the field excitation is automatically controlled and there is no need for manual removal or resynchronization.

Question 5

The rotor must have the same number of poles as the .&#10;A)cage&#10;B)main&#10;C)stator&#10;D)auxiliary

Accepted Answer

The stator is the stationary part of the motor that surrounds the rotor. The number of poles in the stator's magnetic field determines the speed and torque of the motor. Therefore, the rotor must have the same number of poles as the stator in order to interact properly and produce the desired performance. The stator is the stationary part of the motor and contains the magnetic field, so the rotor must have the same number of poles as the stator in order to synchronize with the magnetic field and operate efficiently.

Question 6

Synchronous motors are constructed almost exactly like alternators.

Accepted Answer

Synchronous motors are very similar in construction to synchronous generators (alternators), with some minor differences in the stator and rotor designs. Synchronous motors have a rotor and a stator like alternators, with the difference being that the rotor of a synchronous motor rotates at the same speed as the stator's magnetic field, while in an alternator the rotor spins faster than the stator's magnetic field.

Question 7

AC loads generally have a lagging power factor.

Accepted Answer

AC loads such as motors and transformers often have inductive components that cause the current to lag behind the voltage, resulting in a lagging power factor. AC loads, such as motors and transformers, typically have inductive components that cause the voltage and current waveforms to be out of phase, resulting in a lagging power factor.

Question 8

A disadvantage of the synchronous motor equipped with a brushless exciter is that brush sparking is eliminated.

Accepted Answer

The statement is incorrect because the elimination of brush sparking is actually an advantage of using a brushless exciter in a synchronous motor. The statement is incorrect. The elimination of brush sparking is actually an advantage of the synchronous motor equipped with a brushless exciter.

Question 9

A distinguishing feature of the synchronous motor is that it runs without slip at a speed determined by the frequency of the connected power source and the number of poles it contains.

Accepted Answer

A synchronous motor runs without slip and its speed is determined by the frequency of the power source and the number of poles it contains. This statement is true. The synchronous motor is designed to run at a speed that corresponds to the frequency of the power source and the number of poles in the stator. Unlike induction motors that have slip and rotate slightly slower than the synchronous speed, synchronous motors operate at synchronous speed without slip.

Question 10

The synchronous motor sets up a rotating field through coils energized by alternating current.&#10;A)DC&#10;B)stator&#10;C)available&#10;D)contactor

Accepted Answer

The stator coils of a synchronous motor are energized by alternating current to set up a rotating magnetic field. This field interacts with the magnetic field of the rotor to produce rotation. Choice A is incorrect because DC cannot produce a rotating magnetic field. Choice C is too vague and does not provide any coherent explanation. Choice D is also incorrect because a contactor is a type of electrical switch and does not relate to the operation of a synchronous motor. The stator of a synchronous motor is the stationary part that contains coils that are energized by alternating current to set up a rotating magnetic field. Therefore, the correct choice is B) stator. The other choices are not relevant to the operation of a synchronous motor.

Deck 39: Synchronous Motor Operation