FiltersDone

Question type

Essay

Multiple Choice

Short Answer

True False

Matching

Exam 19: Motor Maintenance and Troubleshooting

Show Answer

Share

---

All types

Filters

Study FlashcardsPractice ExamLearn

Question 1

Multiple Choice

Review LaterAdd Note

Review Later

To test a squirrel-cage rotor, it is necessary to access the ____ concealed inside the rotor laminations.

A) copper coils
B) rotor bars
C) slip rings
D) fuses

E) B) and C)
F) A) and B)

Correct Answer

verified

Show Answer

Question 2

Multiple Choice

Review LaterAdd Note

Review Later

In direct current machines, the segments between commutator bars can become shorted due to a buildup of ____ caused by the wearing of the brushes.

A) copper
B) carbon
C) iron
D) steel

E) A) and C)
F) A) and B)

Correct Answer

verified

Show Answer

Question 3

Multiple Choice

Review LaterAdd Note

It is possible to determine if the motor is connected wye or delta by checking the ____.

Rotating a rotor ____ by hand will generally reveal a bad bearing.

Brushless synchronous motors contain a separate two-phase winding mounted on the rotor shaft-this winding is used to supply direct current to the main rotor winding-as well as rectifiers and fuses.

If a three-phase, wye-connected, dual-voltage motor is connected to a 240-V line, the motor windings are connected in series.

Dual-voltage motors are generally characterized as having more than two T leads. Seven-lead motors are the most common, but some motors have nine leads.

To test an armature for an open winding, connect the leads of an ohmmeter to two adjacent commutator bars.

A lubrication schedule is the best method of ensuring that motors are not overlubricated in some cases and never lubricated in other cases.

If one stator winding in an AC motor is shorted, testing the resistance between all the ____ generally shows one reading to have a higher resistance than the other two.

A device that is often used to test an armature is called a ____, which is a device constructed by wrapping a coil of wire around a set of V-shaped laminated cores.

Slip ring rotors contain ____ slip ring(s) , which is(are) used to connect direct current to the rotor winding while the motor is in operation.

Slip ring rotors contain two slip rings, which are used to connect direct current to the rotor winding while the motor is in operation.

The rotor of a squirrel-cage motor is easy to test in the field.

Most of the AC motors in industry are ____-phase.

Testing the field windings of an AC motor is very similar to testing the stator windings in a direct current machine.

If periodic preventive maintenance on electric motors is not desired or feasible, vibration sensors on the motor shaft can warn of impending bearing failure before it occurs.

There is no set standard for determining if a motor winding is good or bad. Some industries use a standard of 1 megohm per 100 volts. Others use 2 megohms per 100 volts. Other industries use a flat standard such as 1.5 to 15 megohms = Poor, 15 to 50 megohms = Fair, and 50 to ____ megohms = Good.

When identifying the proper relationship of motor windings, remember that the circuits that exhibit continuity between two leads must be identified as pairs, but do not let the ends of the leads touch anything.

Periodic maintenance of direct current machines includes testing the insulation on the ____ and the armature with a megohmmeter.