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Chapter 8

Chapter 8 Motor Failure Trade Test

QuestionAnswer
More motors fail due to ____ than any other reason. Overloading
_____ unbalance is the unbalance that occurs when lines are out-of-phase. Phase
Single phasing is the maximum condition of ____. Voltage Unbalance
All motors produce ____ as they convert electrical energy to mechanical energy. Heat
A ____ is the application of too much load to a motor. Overload
______ causes metal parts to rust and motor coil insulation to lose some of its insulating driven pulley. Moisture
The ____ of a belt is measured from the center of the drive pulley Span
____ is usually corrected by placing shims under the feet of the motor or driven equipment. Misalignment
A motor ______ is an imperfection created during the manufactured motor. Defect
Motor _____ is any damage that occurs to a properly manufactured motor. Damage
Water used to clean a motor should no exceed _____ degrees F. 200
For normal operation, electric motor oil should be added to sleeve bearings of motors after ____ years. 3
For normal operation, motor ball bearings should be lubricated after _____ years. 1-10
Motors other than ____ types can usually be mounted in any position. Drip Proof
True/False: Excessive heat is a major cause of motor failure. True
True/False: The insulation class of motors is given in C and/or F. True
True/False : As phase unbalance increases, motor temperature decreases. False
True/False: Motors with a voltage unbalance require derating. True
True/False: Voltage unbalance causes blackening of all stator windings. False
True/False: Single phasing of a delta-connected motor causes severe burning and distortion to two or more phase coils. False
True/False: Over cycling occurs when a motor is repeatedly turned ON or OFF. True
True/False: Couplers compensate for misalignment of the motor and driven load. True
True/False: To force dry a motor, heat is applied for approximately 18-30 hours. True
Whenever more then ____% voltage unbalance is measured, the power company should be notified. A. 2 B. 4 C. 6 D. 8 A 2
When one of the 3-Phase lines of a motor no longer delivers voltage to the motor, the motor will ____. A. not operate B. operate on one phase C. operate on two phases D. not be affected C operate on two phases
Surge voltage is ____ voltage. A. higher than normal, temporary B. higher than normal, permanent C. lower than normal, temporary D. lower than normal, permanent A higher than normal, temporary
If a motor is drawing rated current, it is ____. A. barely working B. working in its lower mid-range C. working in its upper mid-range D.working to its maximum D working to its maximum
Motor starting current is usually ____ times the full-load running current of the motor. A. 2 to 3 B. 3 to 4 C. 4 to 5 D. 5 to 6 D 5 to 6
When a motor application requires that the motor be cycled often, ____. A. use a 50 degree C motor B. use a 1.25 or 1.35 service factor motor C. provide additional cooling D. A, B, and C D A, B, and C
When cleaning a motor with water, the water pressure should not exceed ____ psi. A. 10 B. 15 C. 20 D. 25 D 25
Single phasing can be reduced by using the ____. A. proper size dual-element fuse B. correct heater sizes C. both A and B D. neither A nor B C Both A and B
When a motor has failed due to overloading, ____. A. all motor windings will be blackened evenly B. there will be obvious damage to the insulation C. there will be isolated areas of damage D. A, B, and C A. all motor windings will be blackened evenly
Belt deflection should equal ____" per inch of span. A. 1/64 B. 1/16 C. 1/4 D. neither A, B, nor C A 1/64
Type of problem: The first few turns of the windings are burnt and opened. Voltage Surge
Type of problem: All windings are burnt. Overload
Type of problem: One-third of the windings are burnt. (delta connection) Single Phasing
Type of problem: Two-thirds of the windings are burnt. (wye connection) Single Phasing
Created by: aganotisi
 

 



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