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A ____ occurs when the load connected to the motor exceeds the full-load torque rating of the motor.
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The motor _____ is a safety margin for the motor overloads.
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Chapter 7
Chapter 7 Motor Protection
| Question | Answer |
|---|---|
| A ____ occurs when the load connected to the motor exceeds the full-load torque rating of the motor. | Overload |
| The motor _____ is a safety margin for the motor overloads. | Service Factor |
| ______ temperature is the temperature of the air around a piece of equipment. | Ambient |
| Motor starters are manually or _____ controlled. | Magnetically |
| The Square Root of 3 = _____ | 1.732 |
| _____ LRC is the locked rotor current with power factor and efficiency considered. | True |
| A ____ with appropriate scales is used to test fuses. | Multimeter |
| A _____ circuit occurs when current does not follow its designed path. | Short |
| Overloads are usually between one and ____ times the normal current level of the circuit. | 6 |
| The LRC is usually from four to _____ times the motor's FLC. | 8 |
| The common ambient temperature limit for motors is _____ degree C. | 40 |
| The most commonly used ___ are fuses and circuit breakers. | Starting Protection |
| A typical combination starter combines the parts of a ____ with the motor starter. | Safety Switch |
| _____ panels house the fuses or CB's that protect general lighting and appliance circuits. | Power |
| The three positions of a CB are ON, _______, or Off. | Trip |
| True/False: An over current may be an overload current or a short-circuit current. | True |
| True/False: Fault current may return to ground or the power source. | true |
| True/False: A combination starter with CB's is less expensive than a combination starter with fuses. | False |
| True/False: A hot power line is any power line that is not grounded. | True |
| True/False: Overloads occur in most circuits at modest levels. | True |
| True/False: High inrush current increases as the motor accelerates. | False |
| True/False: The motor starter also protects a motor while it is running. | True |
| True/False: One heater is required to protect 3-Phase motors. | False |
| True/False: An overload in a motor decreases the temperature of the windings. | False |
| Current Equals ____. A. voltage times resistance. B. voltage divided by resistance. C. resistance divided by voltage. D. resistance plus voltage. | B. voltage divided by resistance |
| A 10 HP motor with a service factor of 1.25 can safely develop _____ HP. A. 8.75 B. 10 C. 11.25 D. 12.5 | D. 12.5 |
| NEC Table 420.250 deals with ____ motors. A. DC, 1/4-200 HP B. 1-Phase, AC, 1/6-10 HP C. 2-Phase, 1/2-200 HP D. 3-Phase, AC, 1/2-200 HP | D. 3-Phase, AC, 1/2-200 HP |
| NEC 240.6 lists standard ampere ratings of fuses and fixed-trip CBs at every 5A from 15A through _____A. A. 25 B. 50 C. 75 D. 95 | B. 50 |
| The incoming voltage to a CB should be withing _____% or _____% of the motor's FLC. A. 100;115 B. 115;125 C. 125;140 D. 140;150 | B. 115;125 |
| A thermal overload relay operates on the principle that as the level of current increases, the temperature across the heating element. A. is not affected B. fluctuates C. increases D. decreases | C. increases |
| The function of an OCPD is to protect the ____ from a short circuit or ground. A. branch-circuit conductors B. control equipment C. motor D. A, B, and C. | D. A, B, and C |
| Generally, safety switches used to protect motors shall be ____. A. located within sight of the motor controller. B. installed to disconnect the motor and motor control circuit C. both A and B D. neither A nor B | C. both A and B |
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