MARE-306 Lab Test 2

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One major advantage of a separately-excited shunt motor is that the motor can be operated __________ its rated nameplate speed.

above

Anytime a motor can be operated on different voltages, it is better to select the high voltage confi guration because the motor will draw less ________.

amperage

Three-phase induction motors ________ (are/are not) the most effi cient type of electric motors available next to synchronous motors.

are

The __________ windings have much less resistance than the field windings.

armature (one)

The only sure method to reverse the direction of rotation on a cumulative compound motor is to reverse the __________ connections.

armature (three)

The direction of rotation on a DC shunt motor can be reversed by either reversing the field connections or the ___________ connections.

armature (two)

The maximum speed of a self-excited shunt motor is determined by the __________.

armature current

The process of reducing the field current of a separately-excited shunt motor is called __________.

field weakening

A three-phase induction motor has a _______ (high/low) power factor.

high (one)

If the phase halves are connected in series on a three-phase motor, the motor is confi gured for ______ (high/low) voltage operation.

high (two)

A DC compound motor provides ________ (higher/lower) starting torque than a shunt motor.

higher (three)

The windings on a three-phase motor are __________ (identical/different).

identical

When a DC motor is connected in the separately-excited configuration, as the field current is decreased, the motor speed ____________ (increases/decreases).

increases

The two most common categories of three-phase motors are synchronous and ____________.

induction (one)

About 95% of the motors used in industry are __________ motors.

induction (two)

If the winding halves of a dual-voltage delta motor are connected in parallel, the motor is wired for __________ operation.

low voltage

Some times, the three phases in a three-phase motor are divided in half to allow ______________ operation.

low/high voltage

Most _______________ use three-phase induction motors because of their effi ciency and easy speed control through gear of belt drive systems.

machine tools

In many cases, the switching of lines to reverse a three-phase motor is accomplished through two sets of _____________.

magnetic contacts

An advantage of a self-excited DC shunt motor is that it is able to ___________ its speed over a wide load range.

maintain

Devices used to switch the lines to a three-phase motor often include built-in safety __________ to prevent phase-to-phase shorts.

measures

How do you calculate Slip?

((Synchronous Speed RPM - Actual Speed RPM)/Synchronous Speed RPM)*100

How to calcualte kW (S.I units)

(Torque (N-m) *Speed (RPM))/ 9549

How to claculate Hp (U.S units)

(Torque (ft-lb) *Speed (RPM))/ 5252

A DC compound motor provides better _______ control than a series motor.

speed

Large conveyor systems rely on the good _______________ of the three-phase induction motor to provide constant speed even if the load changes.

speed regulation

Two common types of induction motors are ______________ and wound rotor.

squirrel cage

The square root of 3 is __________.

1.73 (one)

For a 3-phase circuit, the product of the line voltage and current must be multiplied by __________.

1.73 (two)

A three-phase motor usually has a service life of _____ years or better.

10

Each phase in a 3-phase circuit is __________ electrical degrees apart.

120

By switching ______ of the supply lines to a three-phase motor you can reverse the direction of rotation.

2

The average range of slip for squirrel-cage induction motors is 2% to ____%.

6%

How to calculate efficiency

Efficiency = (Power Out/ True Power) *100

The industry standard method for reversing a three-phase motor is to switch lines L1 and ___.

L3

How do you calculate Apparent Power in 3-phase circuit?

P(a) = V(line) * I(line) *1.73

How do you calculate Power Factor?

Power Factor = True Power / Apparent Power

A DC __________ motor is a motor with a field connected in both series and in shunt with the armature.

compound

If the series and shunt windings in a compound motor are connected so that their magnetic fields have the same polarity, the motor is configured as a __________ compound motor.

cumulative

In a ________ confi gured three-phase motor, the phase windings are connected end-to-end to form a closed loop.

delta

The __________ compound motor has very few applications and is avoided for the most part.

differential

A DC shunt motor ________ (does/does not) provide high starting torque.

does not

A DC shunt motor has its fi eld windings connected in ________ with the armature.

parallel

The two sets of contacts used to reverse a three-phase motor are often controlled using __________, one for forward and one for reverse.

pushbuttons

A DC shunt motor will not __________ if there is no load connected to it, unlike a DC series motor.

run away

When the shunt field is connected to the same power supply as the armature, it is called a _______________ shunt field.

self-excited

When a separate power supply is used for the shunt field, it is called a _____________ shunt field.

separately-excited

The input current on each line to a three-phase motor should be ___________ (the same/different).

the same

The _______ three-phase distribution system is the safest of the two systems.

wye (one)

Two wiring confi gurations for a three-phase motor are the _____ and delta confi gurations.

wye (two)


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