Question 1

What may result if severe bearing wear occurs in either large or small motors?

Accepted Answer

Severe bearing wear on either large or small motors may result in actual contact between the rotor and the stator.

Question 2

Briefly describe two methods that are used in lubricating motors.

Accepted Answer

Methods of lubricating motors include the following:
• Small motors with sleeve bearings have oil holes with spring covers.
• The bearings of larger motors are often provided with an oil ring that fits loosely in a slot in the bearing. The oil ring picks up oil from a reservoir located directly under the ring.
• Many motors are lubricated with grease.

Question 3

The formula Rm = KV + 1 is used as part of a balance test measuring the phase currents under load.

Accepted Answer

The formula Rm = KV + 1 is actually used to calculate the rotor resistance in a squirrel cage induction motor. It is not used as part of a balance test measuring the phase currents under load.

Question 4

A(n) ____________________ is used to measure insulation resistance.

Accepted Answer

The answer of A(n) ____________________ is used to measure insulation...

Question 5

A(n) ____________________ motor is a self-contained drive made up of a ball-bearing motor and a speed-reducing gear box.

Accepted Answer

The answer of A(n) ____________________ motor is a self-contained drive...

Question 6

A(n) ____________________ is an instrument consisting of an electromagnetic yoke and winding excited from an AC source that can be used to locate short-circuited coils.

Accepted Answer

The answer of A(n) ____________________ is an instrument consisting of...

Question 7

The bars of a squirrel-cage ____________________ can be broken if the motor is subjected to severe jarring, vibration, or overheating.

Accepted Answer

The answer of The bars of a squirrel-cage ____________________ can...

Question 8

List two factors that would influence a plant maintenance engineer's decisions for frequency and thoroughness in systematic inspection and servicing of motors.

Accepted Answer

The answer of List two factors that would influence a...

Question 9

The field coils of alternators can be checked for impedance by applying a low-frequency high voltage to each coil and measuring the current.

Accepted Answer

The field coils of alternators are typically checked for insulation resistance and continuity, not impedance, using a megohmmeter or similar device to apply a DC voltage. Impedance testing with a low-frequency high voltage is not a standard procedure for field coils.

Question 10

Briefly describe the repercussions of insufficient oil and excessive oil in a motor.

Accepted Answer

The answer of Briefly describe the repercussions of insufficient oil...

Question 11

A tachometer is an instrument used to check the speed of a motor.

Accepted Answer

A tachometer is used to measure the rotating speed of a shaft or disk in a motor.

Question 12

A value of insulation resistance slightly below the recommended approximate value does not necessarily indicate that immediate repair is required. What course of action should be taken by an electrician in this situation?

Accepted Answer

The answer of A value of insulation resistance slightly below...

Question 13

The value of insulation resistance in megohms (1,000,000 ohms) is used as an indication of insulation efficiency.

Accepted Answer

This statement is true. Insulation resistance is used as an indication of the efficiency of electrical insulation. Higher insulation resistance indicates better insulation efficiency.

Question 14

In a good preventive maintenance program with detailed checks, the person in charge should have a history on file for every motor in the plant; entries should include inspection dates, descriptions of repairs, and the costs involved.

Accepted Answer

This is correct. A good preventive maintenance program should keep a detailed history on file for every motor in the plant, including inspection dates, descriptions of repairs, and the costs involved. This information can help inform future maintenance decisions and identify any recurring issues.

Question 15

In a(n) ____________________ test, high but equal current readings in all three phases indicate an overloaded motor.

Accepted Answer

The answer of In a(n) ____________________ test, high but equal...

Quiz 25: Summary Review of Units18-24