1022 Year end review - Theory

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Armatures are wound to provide high voltage, high current or some specific combination of voltage and current. Which type of winding provides moderate voltage and moderate current?

Frogleg-wound

Permanent magnet motors have _____ efficiency than conventional field-wound motors.

Higher

A compound motor has _____ field windings.

Series and Shunt

Small permanent magnet motors that have lightweight rotors are often used as _____.

Servomotors

The DC motor, known as a "constant speed motor," is the _____ motor.

Shunt

When the field winding of a DC motor is connected in parallel with the armature, the motor is called a _____ motor.

Shunt

When a motor is connected differential compound, the _____ determines the direction of rotation of the motor at no load or light load.

Shunt Field

The squirrel-cage rotor code letters indicate the shape (type) of rotor bars. Different types of bars have a large effect on the _____ of a motor.

Starting Torque

The rotating part of a generator is called the _____.

Armature

The _____ ride against the commutator segments and are used to connect the armature to the external circuit of the DC machine.

Brushes

In three-phase power systems, the delivered power _____.

Never falls to zero

When calculating the power of a pure resistive load, the voltage and current are in phase with each other and the power factor is _____.

One

Conductive compensation is accomplished by connecting the compensating winding in _____ with the armature.

Series

The series generator has only a series field, which is connected in _____ with the armature.

Series

The _____ motor can operate on either AC or DC voltage.

Universal

The set of squirrel-cage bars on the rotor of a synchronous motor is used to start the motor and is known as the _____.

amortisseur winding

The output shaft of a stepping motor _____.

moves through a specific angle for each input pulse

A delta-connected set of windings has a phase current of 10 A. What is the line current?

17.32 A

A motor is operating at 3450 RPM and is producing a torque of 32 lb-in. What is the output horsepower of the motor?

1.75 HP

Line voltage and phase voltage are the same in the _____ connection.

Delta

A delta connected set of windings has a phase voltage of 100 V. What is the line voltage?

100 V

Three-phase voltages are _____ out of phase with each other.

120°

A delta-connected three-phase alternator is driving a wye-connected resistive load. The alternator output voltage is 480 V. The load resistors are 12 Ω each. What is the phase current in the alternator?

13.33 A

The horsepower rating of three-phase motors and the kilovolt-ampere rating of three-phase transformers are about _____ greater than for single-phase motors or transformers with a similar frame size.

150 Percent

A wye-connected alternator that has phase voltages of 277 V is feeding two loads. The first load is wye-connected inductors that have 40 Ω of XL. The second load is delta-connected capacitors that have XC of 60 Ω. How much is the alternator phase current?

6.93 A

In a balanced three-phase system, the conductors need be only about _____ the size of conductors for a single-phase, two-wire system of the same kilovolt-ampere (kVA) rating.

75 Percent

What is a device that converts mechanical energy into DC electrical energy?

A Generator

The speed regulation of a DC motor is proportional to the _____.

Armature resistance

The motor that does not contain a wound armature, commutator, or brushes is the _____ motor.

Brushless DC

What is the component of a DC generator that converts the armature AC into DC?

Commutator

The universal motor has a wound armature and brushes like an AC motor, as well as an added component, the _____.

Compensating Winding

A generator containing both series and shunt fields is called a _____ generator.

Compound

The relationship of the strengths of the two fields in a generator determines the amount of _____.

Compounding

A three-phase connection in which three separate inductive loads have been connected together is a(n) _____ connection.

Delta

A compound generator has both series and shunt field windings. When those windings are connected so their fields oppose each other in the production of magnetism, that connection is called _____.

Differential-Compound

Armatures are wound to provide high voltage, high current, or some specific combination of voltage and current. Which type of winding provides low voltage and high current?

Lap-Wound

In a three-phase connection, what is the voltage measured between the lines?

Line Voltage

A device that converts electrical energy into mechanical energy is called a(n) _____.

Motor

Shunt generators contain only a shunt field winding connected in _____ with the armature.

Parallel

In a three-phase connection, what is the voltage measured across a single winding?

Phase voltage

What provide(s) the magnetic field necessary for the operation of a DC machine?

Pole Pieces

A(n) _____ motor operates on the principle that like magnetic poles repel.

Repulsion

Three lines supply power to a three-phase motor. If one of these lines should open, the motor will be connected to single-phase power. This condition is known as _____.

Single Phasing

In a wye-connected system, the line voltage is higher than the phase voltage by a factor of _____.

Square root of three

The _____ winding is made of many turns of small wire and is located at the top of the stator core of a split-phase motor.

Start

If a three-phase load is a pure reactive load, then the power calculated has units of _____.

VARs

Armatures are wound to provide high voltage, high current, or some specific combination of voltage and current. Which type of winding provides high voltage and low current?

Wave-wound

Line current and phase current are the same in the _____ configuration.

Wye

In single-phase motors such as the resistance start induction-run motor, the start winding is disconnected by the _____.

centrifugal switch

A compound generator has both series and shunt field windings. When those windings are connected so they aid each other in the production of magnetism, that connection is called _____.

cumulative-compound

Series field windings are connected in series with the armature. They are wound with _____ turns of fairly _____ wire.

few; large

The output voltage of a generator is usually controlled by the amount of _____.

field excitation current

Multispeed fan motors achieve multiple speeds by inserting additional _____ in series with the run winding.

inductance

The alternator must supply the _____ for each of the loads.

line current

Shunt field windings are connected in parallel with the armature. They are wound with _____ turns of fairly _____ wire.

many; small

The _____ winding is made of a few turns of large wire and is located at the bottom of the stator core of a split-phase motor.

run

In a generator, the _____ permits part of the current that normally flows through the series field to flow through the resistor.

series field shunt rheostat

Split-phase motors operate on the principle of a _____ magnetic field.

rotating

Selsyn motors operate on _____ voltage.

Sigle Phase


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