Motor Controls 31-33, 37, 41, 42

What electrical test instrument should be used to test a component for continuity? (Continuity means to determine if there is a complete circuit through the component.)

ohmmeter

Referring to the figure below, when the fast button is pressed in an attempt to start the motor, the normally _______.

open contacts of control relay FR will prevent the high-speed starter F from energizing

Referring to the figures above, what size conductor should be used if a 15-hp three-phase squirrel cage induction motor is connected to a 230-volt line and the conductors are run in conduit to the motor? Copper conductors with THWN insulation are to be used for the motor connection.

#6 AWG

Referring to the figures above, what size conductor should be used if a 50-hp three-phase squirrel cage induction motor is connected to a 575-volt line and the conductors are run in conduit to the motor? Copper conductors with THWN insulation are to be used for the motor connection.

#6 AWG

In the above figure, the voltmeter should indicate ____.

0 Volts

In the above figure, the voltmeter will indicate _____.

0 volts when the switch is closed

Referring to the figure above, what is the full running current of a 1-1/2-hp, single-phase AC motor connected to a 230-volt line?

10 Amperes

What is the locked-rotor current for a 30-hp, three phase squirrel cage motor with a code letter S connected to a 200 volt line? See the figure above.

1472 Amperes (1470?)

Refer to the circuit shown above. Assume that the fourth speed pushbutton is pressed. Also assume that the motor starts in the lowest speed and accelerates to the second speed, but never reaches the third speed. Which of the following could cause this problem?

TR2 timer coil is defective.

Referring to the figure below, _____. (lol get wrecked)

TR3 is the high limit switch

Referring to the figure below, thermostat ______.

TS2 is normally open

In the circuit shown above, assume that the motor will operate in the forward direction, but will not start in the reverse direction. When the reverse pushbutton is pressed, meter B indicates the line voltage. What is the most likely problem?

The normally closed section of the forward pushbutton is open

Three-speed consequent pole motors can be wound to produce ______, _____, and _______.

constant horsepower, variable torque, and constant torque

Referring to the figure below, when coil TR energizes, ______.

contact TR will close immediately, energizing coil CR

The starting current and speed of a wound rotor induction motor are controlled by adding or subtracting resistance___________________________

in series with the rotor circuit

If the number of poles in a squirrel cage motor is doubled, the speed of the motor _______.

is cut approx. in half

In the above figure, the voltmeter will indicate _____.

line voltage

Referring to the figure above, if contact CR, re-opens before contact 2M₂ closes to seal the circuit, a contact ______ condition exists.

race

Referring to the figure below, the relay CR ______.

remains energized when 1M starter is de-energized

A characteristic of synchronous motors that is different than squirrel cage or wound rotor induction motors is ______.

they operate at the speed of the rotating magnetic field

Referring to the figure above, to permit the circuit to alternate operation of the two pumps, or permit the operation of one pump only, a _____.

three position selector switch is placed in series with the pressure switch

Referring to the figure below, each of the 11-pin control relays have ________.

three sets of contacts

Four-speed consequent pole motors have ________.

two windings, both of which are reconnectable

Referring to the figure below, the second motor speed will be achieved _____.

when the first speed button and then the second speed button are pressed in order, followed by a 3 second time delay

Consequent pole motors have _______.

a single winding for two speeds

Referring to the figure below, with only one overload contact shown, the use of _____.

a three-phase overload relay is apparent

A synchronous motor is started by _______.

accelerating the motor to as high a speed as possible from the squirrel cage winding and then applying the DC field excitation

Referring to the figure below, which contact is used to prevent the motor from operating in the second speed _____.

1CR(subscript)4

Generally, with an AC three-phase wound rotor induction motor, resistance is introduced into the rotor circuit when the motor _____. a. accelerates b. reaches top speed c. a or b above d. neither a or b above

D. neither a or b above

Referring to the figure below, when the timing relay coil TR is energized, the normally closed TR contact _________.

opens after a preset time delay and the normally open contact (TR) closes at the same time

With a synchronous motor, an independent magnetic field is established by a _____.

rotor energized by direct current through slip rings mounted on the shaft

With a consequent pole motor intended to operate with three speeds, if one stator winding was wound with six poles and the second was reconnectable for two or four poles, the motor would develop synchronous speeds of ______, _______, and _______.

1200 rpm, 3600 rpm, and 1800 rpm

What is the overload ampere rating for a 60-hp three-phase induction motor having a nameplate rating of 154 amperes and a marked service factor of 1.20?

193 Amperes

Referring to the figure above, what will be the full load current rating of a 125-hp, 2300-volt synchronous motor to be operated at 90% power factor?

27.5 Amperes

What is the locked-rotor current for a 20-hp, three-phase squirrel cage motor with a code letter G connected to a 240 volt line? See the figure above.

286 Amperes

Motor control centers used throughout industry have enough energy in an arc-fault condition to kill a person standing ____ feet away.

30

What is the overload ampere rating for a 20-hp three-phase induction motor having a nameplate rating of 27 amperes and a temperature rise of 38°C?

34 Amperes

Referring to the figure above, what is the neutral current for a 25-hp, 460-volt two-phase motor?

40.9 Amperes

Referring to the figure above, what is the full running current of a 7-1/2-hp, single-phase AC motor connected to a 200-volt line?

46.0 Amperes

Referring to the figure above, what is the neutral current for a 60-hp, 575-volt two-phase motor?

74.73 Amperes

Referring to the figure above, what will be the full load current rating of a 75-hp, 575-volt synchronous motor to be operated at 80% power factor?

77.5 Amperes

The amount of torque developed by an induction motor is determined by the ___________,______________,_________ and __________. ( I don't know why this is fill in the blank)

All of the above. The strength of the magnetic field of the stator winding. The strength of the magnetic field of the rotor The phase angle difference between the rotor and the stator magnetic fields

The primary test instruments used by electricians for troubleshooting a control circuit are _____, ____, and _____.

Ammeter, voltmeter, and ohmmeter

A brushless synchronous motor results in the elimination of _______, ______, and ______.

Brushes, Collector rings, Commutators

An out-of-step relay (OSR), provided on automatic synchronous starters to protect the starting windings, will open its normally closed contacts when _______. A. the motor returns to a synchronized state after leaving it B. the amount of current induced in the field windings drops below a value determined by the core settings of the out-of-step relay C. both a and b above D. neither a or b above

D. neither a or b above

Generally, wound rotor motors are ________. A. started under load with their slip rings open B. started under load with their slip rings shunted together C not started under load with their slip rings open D. not started under load with their slip rings shunted together

D. not started under load with their slip rings shunted together

When starting a synchronous motor, _______.

DC excitation current should not be connected to the rotor

With a synchronous motor, the rotor's _______.

DC is supplied through slip rings from an external source or small DC generator attached to the end of the rotating shaft

The most common squirrel cage motors used in industry fall into the Design _____ classification.

Design B

In the circuit shown above, assume that the motor is not running. When the forward or reverse pushbuttons are pressed, the motor will not start. Which of the following could NOT cause this problem?

F coil is open

The rotor leads of a wound rotor induction motor are marked ______.

M1, M2, and M3

In the circuit shown above, assume that the motor is operating in the forward direction. If the reverse pushbutton is pressed while the motor is still running, which meter should indicate line voltage?

Meter C

In the circuit shown below, when the reverse pushbutton is pressed, which meter should indicate line voltage?

Meter D?

In the circuit shown above, assume that the motor is operating in the forward direction. Which meter should indicate line voltage?

None

Referring to the figure below, the pressure switch is a ______.

Normally closed switch held-open

A motor is tripping on overload. The nameplate indicates a full load current value of 132 amperes. When the motor is operating, ammeter readings indicate that phase I has a value of 131 amperes, phase 2 has a value of 178 amperes, and phase 3 has a value of 130 amperes. What is the most likely problem with this motor?

Phase 2 is shorted or grounded

In an AC three-phase wound rotor induction motor, speed is varied by adjusting the controller's ________.

Resistance

In the circuit shown above, assume that the fourth speed pushbutton is pressed. Also assume that the motor accelerates to the third speed, but never reaches the fourth speed. Which of the following could cause this problem?

S3 contactor coil is defective.

What is the minimum size NEMA starter that should be used to connect a 100-hp three-phase squirrel cage motor connected to a 230-volt line?

Size 5 Starter

A motor has tripped out on overload. What is the most logical first step in troubleshooting this problem?

Use an ammeter to measure the running current of the motor and compare that value to the nameplate full load current

A polarized field frequency relay consists of ________, ______, and ______.

a direct-current coil, a pivoted armature, and an induced field-current coil

Plunger-type voltage testers are sometimes preferred over voltmeters because they _____.

are not susceptible to ghost voltages

For which of the following would you not use an NEC table? a. conductor size b. motor overload size c. short circuit protection size d. ground fault protection size

b. motor overload size

2. Which type of short-circuit protective device is least likely to be used? A.dual-element time delay fuse b. non-time delay fuse C.Inverse time breaker D.all the above are used extensively

b. non-time delay fuse

Clamp-on type ammeters ______.

can be used without breaking the circuit

The speed of a synchronous motor is determined primarily by the ______.

frequency of the connected power source and the number of poles the motor contains

With a squirrel cage motor, doubling the poles can be accomplished by reversing current through _________.

half a phase winding

An AC three-phase wound rotor induction motor has ______starting torque and ______starting current.

high, low

If the windings of a star-delta motor are such that the series delta connection gives the high speed and the parallel wye connection gives the low speed, the ________.

horsepower rating is the same at both speeds

The field discharge resistor is connected _____.

in parallel with the rotor winding

With regard to multispeed controllers, if the phases between the high- and low-speed windings are reversed, ______, ______, and ______.

motor rotation could reverse, broken casings could result, and motor damage could result.

Another term for an AC three-phase wound rotor induction motor is _____.

slip ring motor

The starting winding of a synchronous motor resembles a(n) _____________________ winding.

squirrel cage