Motors 2

Determine the maximum locked rotor current (LRC) of a 7 1/2 horsepower, 460-volt, 3-phase induction motor with a code letter "M"

105.46

In general, the disconnecting means for motor circuits rated 1,000 volts, nominal, or less, shall have an ampere rating of at least _____ of the full-load current rating of the motor

115%

When the voltage of a dual-voltage motor doubled (115V to 230V) the current is ?

Halved

When rotation is not possible because the stator's field and the rotor's field are equal or parallel to one another, the rotor is ? .

Locked in place

The motor branch-circuit short-circuit and ground-fault protective device shall be capable of carrying the ? current of the motor

Starting

A wound-rotor motor delivers higher starting torque than an induction motor without creating an overload of the electrical system

Starting torque

The provisions of overload protection are not required where this protection might introduce ?

additional or increased hazard

Generally, where overload protection is applied to a motor, that motor is protected against excessive heating due to motor overloads and ?

against damaging currents from shorts and

Generally, in order to calculate the proper size of a separate motor overload protection device for a continuous duty motor, the ? current of the motor is used

nameplate

The NEC requires ? protection of motor installations

overcurrent

DC generators use ? to connect the armature while AC generators use ? to connect to the rotor.

splint rings, slip rings

A DC generator operates on the principle that voltage is induced in a coil of wire when the coil is rotated in a magnetic field

true

Determine the maximum overload protection, using overload relays, when starting current is a problem, for a 15-horsepower, 240-volt, 3-phase, squirrel-cage motor with a nameplate full-load current rating of 45 amperes and a service factor of 1.15

63A

A ? motor is a DC motor that has the field wiring connected in both series and parallel with the armature

Compound

If a capacitor-start motor is to be reversed often, then a ? switch or foot switch can be used to reverse the current through the start with respect to the run windings.

Drum

A ? motor is a DC motor that has the field wiring connected in parallel with the armature

Shunt

Single phase motor types are named for the method used to start the motor

True

To cause the rotor of most single-phase motors to turn in reverse, the NEMA industry standard is to switch the two start leads in the circuit

True

Which of the following conditions is not guarded against by the use of motor overload protection?

d. Mechanical overloading of the driven load