Chapter 8 Motor Failure Trade Test
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
Help!
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| More motors fail due to ____ than any other reason. | Overloading
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| _____ unbalance is the unbalance that occurs when lines are out-of-phase. | Phase
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| Single phasing is the maximum condition of ____. | Voltage Unbalance
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| All motors produce ____ as they convert electrical energy to mechanical energy. | Heat
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| A ____ is the application of too much load to a motor. | Overload
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| ______ causes metal parts to rust and motor coil insulation to lose some of its insulating driven pulley. | Moisture
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| The ____ of a belt is measured from the center of the drive pulley | Span
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| ____ is usually corrected by placing shims under the feet of the motor or driven equipment. | Misalignment
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| A motor ______ is an imperfection created during the manufactured motor. | Defect
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| Motor _____ is any damage that occurs to a properly manufactured motor. | Damage
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| Water used to clean a motor should no exceed _____ degrees F. | 200
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| For normal operation, electric motor oil should be added to sleeve bearings of motors after ____ years. | 3
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| For normal operation, motor ball bearings should be lubricated after _____ years. | 1-10
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| Motors other than ____ types can usually be mounted in any position. | Drip Proof
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| True/False: Excessive heat is a major cause of motor failure. | True
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| True/False: The insulation class of motors is given in C and/or F. | True
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| True/False : As phase unbalance increases, motor temperature decreases. | False
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| True/False: Motors with a voltage unbalance require derating. | True
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| True/False: Voltage unbalance causes blackening of all stator windings. | False
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| True/False: Single phasing of a delta-connected motor causes severe burning and distortion to two or more phase coils. | False
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| True/False: Over cycling occurs when a motor is repeatedly turned ON or OFF. | True
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| True/False: Couplers compensate for misalignment of the motor and driven load. | True
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| True/False: To force dry a motor, heat is applied for approximately 18-30 hours. | True
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| Whenever more then ____% voltage unbalance is measured, the power company should be notified. A. 2 B. 4 C. 6 D. 8 | A 2
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| 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
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| 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
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| 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
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| 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
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| 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
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| When cleaning a motor with water, the water pressure should not exceed ____ psi. A. 10 B. 15 C. 20 D. 25 | D 25
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| 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
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| 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
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| 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
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| Type of problem: The first few turns of the windings are burnt and opened. | Voltage Surge
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| Type of problem: All windings are burnt. | Overload
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| Type of problem: One-third of the windings are burnt. (delta connection) | Single Phasing
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| Type of problem: Two-thirds of the windings are burnt. (wye connection) | Single Phasing
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Or sort by any of the columns using the down arrow next to any column heading.
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