Unit 20 Troubleshooting Electric Motors

Question 1

If a sleeve bearing fails in a small, fractional horsepower motor, the motor is generally replaced. True or false

Answer 1

True

Question 2

An open winding in an electric motor means that

Answer 2

A wire in one winding is broken.

Question 3

There is a short circuit in an electric motor winding when

Answer 3

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

Question 4

An open winding or a shorted winding can be determined with which instrument?

Answer 4

An ohmmeter.

Question 5

A decrease in resistance will cause the amperage to

Answer 5

Increase

Question 6

A ______ may be used to detect resistances in the millions of ohms.

Answer 6

Megohmmeter

Question 7

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

Answer 7

A 20,000 ohm, 5 Watt resistor is recommended.

Question 8

. To determine the capacitance of a capacitor, a _____ should be used.

Answer 8

Capacitor tester

Question 9

State the physical differences between a run and a start capacitor.

Answer 9

A run capacitor is a metal, oil filled can, whereas a start capacitor is dry and the shell is paper or plastic.

Question 10

In a three-phase motor in good operating condition, the resistance

Answer 10

Should be the same across all three windings.

Question 11

Describe what may happen to an electric motor if the drive belt is too tight.

Answer 11

A drive belt that is too tight will strain the bearings so that they wear out prematurely.

Question 12

A loose connection may result in _____ voltage and _____ current at the motor.

Answer 12

Low,high

Question 13

. The amperage can be checked with a _____ ammeter.

Answer 13

Clamp-on.

Question 14

Electric motor roller and ball bearing failure often can be determined by the

Answer 14

Bearing noise.

Question 15

Motor bearings ______ by the air-conditioning and refrigeration technician.

Answer 15

Are occasionally replaced.

Question 16

An open winding in an electric motor means that

Answer 16

A wire in one winding is broken.

Question 17

If there is a decrease in resistance in the run winding,

Answer 17

The motor may draw too much current while it is running.

Question 18

PSC means

Answer 18

Permanent split-capacitor

Question 19

Motor bearing failure with roller and ball bearings can often be identified by the

Answer 19

Bearing noise

Question 20

Mini motors fail because of over tighten belts and incorrect alignment true or false

Answer 20

True

Question 21

The belt tension gauge uses two

Answer 21

O-rings.

Question 22

when using the gauge the center to Center measurements must be taken between the

Answer 22

Two shafts

Question 23

If the drive pulley and driven pulley are not aligned, a strain is imposed on a ____________ of the shaft

Answer 23

Drive mechanism

Question 24

the pulley maybe aligned with the help of a

Answer 24

straightedge

Question 25

when the problem is the pulley or drive mechanism, the air conditioning, heating, and Refrigeration technician or motor expert may be responsible for repair

Answer 25

Technician

Question 26

there are three common electrical motor problems

Answer 26

an open winding
A short circuit from Winding to winding
a short circuit from the winding to ground

Question 27

open windings in a motor can be found with an

Answer 27

Ohmmeter

Question 28

Most electrical problems with an electrical motor are _____, _____, and _____.

Answer 28

shorted windings; open windings or grounded windings

Question 29

If the resistance of the run winding decreases, the ____

Answer 29

Motor will draw too much parent while it’s running

Question 30

If I condenser fan motor grounds out, it will usually ___

Answer 30

Keep running as the current is only going to ground