Motors Level 2

The speed of a wound-rotor motor may be reduced by increasing the ? of the rotor circuit while the motor is running, in order to reduce the current in the rotor windings.

resistance

A brush rigging does not contain ? in its assembly.

resistors

With a(n) ? shunt field, the speed can be regulated by varying the field current, the armature current, or both.

self-excited

A ? is a short-circuited winding, which consists of a single turn of copper wire and acts on only a portion of the stator windings.

shaded-pole

Determine the maximum overload protection by using separate overload protective devices to protect a 20-horsepower, 460-volt, 3-phase continuous-duty motor marked with a temperature rise of 50°C and a motor nameplate full-load current rating of 13 amperes.

14.95 A

When calculating the voltage in the coil for a wye-connected circuit, the voltage is equal to the line voltage divided by ? .

1.73

SEE LESSON 16 QUESTION 1

QUESTION FORMAT TOO STRANGE TO TRANSFER TO QUIZLET

Determine the maximum overload protection, using overload relays, when starting current is a problem, for a 50-horsepower, 208-volt, continuous-duty motor with a motor nameplate full-load current rating of 148 amperes and a service factor of 1.15.

207.2 A

Magnetic motor starters include ? that detect excessive current passing through a motor and are used to switch all types and sizes of motors.

overload relays

A wound-rotor motor regulator is a device that contains high-wattage resistors designed to control the speed of a wound-rotor motor and to operate in variable-speed mode.

True

Fuses and circuit breakers (CBs) are used for ground-fault and short-circuit protection; overload relays are typically used for overload protection.

True

The NEC® requires overcurrent protection of motor installations.

True

The rotor windings of a wound-rotor motor can be in either a wye or a delta configuration.

True

The least expensive reduced-voltage starting method is ? starting.

part-winding

A ? provides a connection to a stationary circuit by riding against a rotating component.

brush

Interpoles reduce sparking at the ? of some DC motors.

brushes

Typical applications of ? motors include fairly hard-to-start loads, like refrigerators, air conditioners, air compressors, and some power tools.

capacitor

A(n) ? in a motor is caused by a load that exceeds the full-load rating of the motor.

overload

The ? connection of a dual-voltage motor is used for low voltage while the ? connection is used for high voltage.

parallel / series

Determine the maximum overload protection when starting current is a problem by using separate overload protective devices to protect a 20-horsepower, 460-volt, 3-phase, continuous-duty motor marked with a temperature rise of 50°C and a motor nameplate full-load current rating of 13 amperes.

16.9 A

A 60-horsepower, 208-volt, 3-phase, continuous duty, squirrel-cage motor is supplied by a motor branch circuit. Calculate the minimum ampacity for the motor branch-circuit conductors.

211.25 A

One 10-horsepower, 208-volt, 3-phase, continuous-duty, induction type Design B motor; one 25-horsepower, 208-volt, 3-phase, continuous-duty, induction type Design B motor; and one 30-horsepower, 208-volt, 3-phase, continuous-duty, induction type Design B motor are supplied by a single motor branch circuit. Calculate the minimum ampacity for the single motor branch-circuit conductors supplying all three motors.

215.6 A

An inverse-time circuit breaker is used for branch-circuit short-circuit and ground-fault protection for a 30-horsepower, 208-volt, 3-phase squirrel-cage motor. Calculate the maximum rating permitted for the circuit breaker.

225 A

A 40-horsepower, 230-volt, 3-phase synchronous motor uses non-time-delay fuses for motor branch-circuit short-circuit and ground-fault protection. Calculate the maximum rating for a non-time-delay fuse.

250 A

What is the maximum rating of the motor branch-circuit short-circuit and ground-fault protective device for a 7 1/2-horsepower, 208-volt, 3-phase squirrel-cage induction motor using time-delay fuses?

45 A

Brushes and ? are used to connect the rotor of a wound-rotor motor to an external set of secondary resistors.

slip rings

A(n) ? motor is a single-phase AC motor that includes a run winding and a resistive start winding used in applications where starting is easy, such as fans, business machines, machine tools, and centrifugal pumps.

split-phase

A ? is the fixed, unmoving part of a motor, consisting of a core and windings, that converts electrical energy to the energy of a magnetic field.

stator

An adjustable, instantaneous trip circuit breaker that is a part of a listed combination motor controller with coordinated protection in each conductor is used for branch-circuit short-circuit and ground-fault protection for a 15-horsepower, 440-volt, 3-phase squirrel-cage motor. Calculate the maximum setting for the instantaneous trip rating of this circuit breaker.

168 A