chapter 15

Squirrel cage rotors are made of metal bars mounted on an iron core.

true

____ motors have stator windings arranged in pairs so that they can be used with two different voltages.

Dual-voltage

Which of the following statements is not true of ECMs?

ECMs have rotors made of coils of wire.

A(n) ____ compressor has a motor that drives its crankshaft by using a belt that connects the motor to the compressor.

open-drive

Field poles are electromagnets whose ____ change as the flow of current alternates in the field windings.

polarities

____ motors are low-torque, single-phase motors that do not use a start winding to produce starting torque

Shaded-pole

____ motors are induction motors used in applications that operate in the fractional horsepower range, such as fans and compressors in capillary tube systems.

Split-phase

A ____ motor is a single-phase induction motor that has a start capacitor wired in series with the start winding.

capacitor-start, induction-run

The ____ close the openings at either end of the motor frame and hold the bearings.

end bells

The two main parts of a motor are the ____.

rotor and stator

Field poles and field windings are often referred to as ____ windings.

stator

Field windings are the wires wrapped around the field poles of the ____.

stator

The ____ is the stationary part of a motor.

stator

The connection between the motor shaft and crankshaft on an open-drive compressor can be made directly by using a coupling.

true

The relationship among applied voltage, counter emf, and current maintains the rotor at a constant speed.

true

A hydraulic unloader can reduce a compressor's load on start-up.

true

A run capacitor provides a signal that is out of phase for added torque during a motor's entire operation.

true

A shaded-pole motor is a type of single-phase motor.

true

An induction motor's frequency must match the frequency of the supplied power.

true

Hermetic compressors require leak-proof electrical connections.

true

A run capacitor remains in the start winding circuit only during start-up.

false

Electric motors are rated at synchronous speed.

false

Generally, single-phase motors are more efficient than three-phase motors.

false

Run capacitors are usually dry electrolytic types of capacitors.

false

Start capacitors are used to assist run capacitors during normal, full-speed motor operation when needed.

false

Motors are not 100% efficient because of ____.

imperfect windings clearances bearing friction Correct! All of the above.

The ____ is the axle-mounted unit that rotates in a motor.

rotor

The ____ is where electrical connections are made to control and power the motor.

motor terminal box

The difference between a motor's synchronous speed and rated full-load speed is called ____.

slip

A ____ capacitor is used only during motor start-up to provide initial starting torque.

start

Motors differ from each other by the amount of starting torque and running torque that they generate.

true

Using measured resistance values and the process of elimination, a technician can identify unmarked hermetic compressor terminals if the motor inside is single-phase.

true

When a motor is slowed considerably by a heavy load, then the current induced in the rotor increases greatly.

true