Question 1

Variable pitch pulleys is a mechanical method of obtaining continuously adjustable speed from .&#10;A)the direct motor drive&#10;B)motor input&#10;C)constant speed shaft&#10;D)the output to the alternator

Accepted Answer

Variable pitch pulleys allow for continuously adjustable speed from a constant speed shaft.

Question 2

The speed of an AC squirrel cage induction motor depends on the frequency of the supply current and .&#10;A)power-factor correction&#10;B)the motor unit size&#10;C)the response accuracy&#10;D)the number of poles of the motor

Accepted Answer

The speed of an AC squirrel cage induction motor is determined by the frequency of the supply current and the number of poles of the motor. The higher the frequency, the faster the motor will run. The number of poles determines the speed at which the motor runs at a given frequency. The speed of an AC squirrel cage induction motor is directly proportional to the frequency of the supply current and inversely proportional to the number of poles of the motor. Therefore, the correct answer is the number of poles of the motor (option D). Power-factor correction, motor unit size, and response accuracy do not directly affect the speed of the motor.

Question 3

Variable-frequency power drives are used on many different types of conveyor systems.

Accepted Answer

Variable-frequency power drives can be used to control the speed of conveyor systems, making them useful in a variety of industries and applications. Variable-frequency power drives can help to control the speed and movement of conveyor systems, making them a valuable addition to many different types of industries and applications.

Question 4

There is only one method used for one or more motors to obtain variable frequency from a fixed-frequency power source.

Accepted Answer

There are actually several methods to obtain variable frequency from a fixed-frequency power source, such as variable speed drives, cycloconverters, and pulse width modulation. There are multiple methods to obtain variable frequency from a fixed-frequency power source, such as pulse-width modulation, variable frequency drives, and cycloconverters.

Question 5

Variable pitch systems are among the lowest-cost methods of achieving variable speed.

Accepted Answer

Variable pitch systems are generally a cost-effective solution for achieving variable speed compared to other methods such as frequency converters or hydraulic transmissions. Variable pitch systems require less complex systems than other variable speed methods such as variable frequency drives, making them a lower-cost option.

Question 6

A variable power unit may be used to control one or more motors at speeds.&#10;A)homogeneous&#10;B)incremental&#10;C)coordinated&#10;D)high

Accepted Answer

The answer of A variable power unit may be used...

Question 7

In cases where more than one motor is involved, all of the motors are connected electrically to the power system of the ____.&#10;A)input source&#10;B)alternator&#10;C)pulleys&#10;D)output source

Accepted Answer

The answer of In cases where more than one motor...

Question 8

A frequency changer may be used to vary the speed of AC squirrel cage induction motors.

Accepted Answer

A frequency changer (also known as a variable frequency drive or VFD) can be used to manipulate the frequency (and therefore the speed) of AC induction motors, including squirrel cage induction motors. A frequency changer, also called a variable frequency drive or VFD, can be used to vary the frequency of the AC power supplied to a motor, which in turn changes the motor's speed. This is commonly used with squirrel cage induction motors to allow for variable speed control.

Question 9

Screw conveyors may be controlled individually by variable drive motors.&#10;A)slave&#10;B)coupled&#10;C)remote&#10;D)series

Accepted Answer

Variable drive slave motors are the best choice for controlling screw conveyors individually as they allow for precise speed control and can be controlled from a centralized location. Coupled motors would require all screw conveyors to operate at the same speed, remote motors would not allow for immediate adjustments, and series motors are not typically used for variable speed control. Variable drive slave motors are the best choice for controlling screw conveyors individually as they can be operated at different speeds and synchronized with other motors to ensure optimal performance of the conveyor system. Coupled motors are connected together and operate at the same speed, thus limiting flexibility in controlling individual screw conveyors. Remote motors may require additional control systems and may not be as efficient. Series motors are not suitable for screw conveyors as they have limited torque control and cannot be operated at variable speeds.

Question 10

Assembly lines make use of variable-frequency power drives.

Accepted Answer

Assembly lines require precision control of motor speed to optimize production efficiency, which is provided by variable-frequency power drives. Variable-frequency power drives are used in assembly lines to control the speed of motors and optimize the production process.

Deck 54: Variable-Frequency Mechanical Drives