Unit 20 Troubleshooting Electrical Motors

What do you do if sleeve bearing fails in a small fractional HP motor?

motor is generally replaced

An open winding in an electrical motor means .....

a wire in one winding is broken

There is a short circuit in an electrical motor when ....

winding conductor is worn bare and touches another part of the conductor that is also bare.

With which instrument can an open or shorted winding be detected?


A decrease in resistance will cause the amperage to .....


What can detect resistance into the millions of ohms?


What size resistor is recommended for shorting a wire across an electrical motor capacitor before checking with an ohmmeter?

20,000 ohm 5W resistor

What can be used to determine the capacitance of a capacitor

Capacitor tester. Many digital multimeters also have the ability to check actual capacitance

What is the physical difference between a start and a run capacitor?

Run - metal can that is oil filled.
Start - dry type and contained in a paper or plastic shell.

A three phase motor, in good operating condition, the resistance across all three windings should be ....


What will happen to an electric motor if a drive belt is too tight?

The bearings will wear out prematurely

How are electrical components checked on a hermetic compressor?

From the outside = open circuit, grounded circuit, short circuit.

What happens if there is a loose electrical conection?

Loose connections = oxidation of copper wire.
Oxidation = electrical resistance that causes more heat. Loose connections result in low voltage and overcurrent conditions.

How can amperage be checked?

clamp on ammeter

How can Electrical motor roller and ball bearing failure often can be determined by ......

the noise

Bearing problems are often caused by .....

belt tension

Shaft problems may be caused by the technician while they remove ........ or ...........


motor balancing problems are usually ..... handled by the heating, air conditioning and refrigeration tech


make sure that the system is not causing any ..... while running


most electrical problems are caused by ........ , ........ or ......... windings

short circuited

Laws of electrical current flow must be used when ............ motors


If the motor is receiving the correct voltage and is electrically sound, check the motor .........


trouble shooting hermetic compressors are different from open motors because hermetic compressors are ..........