EA 150 Chapter 4 Review Questions

A circuit breaker suitable for use as a motor disconnecting means must have a current rating of at least ____.

115% of the motor full-load current

If a squirrel cage induction motor draws 2A of current at 240V and is connected for use on 480V, the amperage will be ___.

1A

Of the following motors, the one most likely to have 15 or 18 motor leads is the _____.

2,400V three-phase motor

If two 10 ohm windings are connected in series for operation on 480V, the total impedance is _____.

20 ohms

The synchronous speed of a 60Hz, three-phase induction motor with two poles is ___.

3,600 rpm

With 240V applied to a total parallel impedance of 5 ohms, the current is ____.

48 A

The total resistance of the stator windings in a three-phase motor, if the windings are connected in parallel and the resistance of each winding is 96 ohms, is ____.

48 ohms

If the stator windings of a dual-voltage motor both have an impedance of 10 ohms and they are connected in parallel, the total impedance is ____.

5 ohms

The most common number of motor leads found on a three-phase Wye-wound motor is ______.

9

Stator windings can best be described as___.

a structure of copper or aluminum wire coils

The main purpose of motor overload protection is to protect the motor ____.

from damaging overload currents

Doubling the voltage on a dual-voltage motor____.

halves the full-load current

The type of a three-phase motor is determined by the _____.

rotor

The synchronous speed of a motor is the ____.

speed at which the magnetic field rotates

The two most common three-phase motor configurations are ____.

wye and delta