1022 Midterm - Delmar Questions

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

never falls to zero

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

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

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

Compound

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

commutator

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

field excitation current

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

higher

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

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

motor

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

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

square root of three

In calculating apparent power (VA) in a three-phase circuit, the phase values of voltage and current are multiplied by _____.

three

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

compounding

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

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

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

series

A compound motor has _____ field windings.

series and shunt

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

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

servomotors

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 three-phase connection in which one end of each of the windings are connected together is called a(n) _____ connection.

wye

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

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

VARs

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

100 V

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

a generator

The rotating part of a generator is called the _____.

armature

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

armature resistance

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

brushes

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

brushless DC

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

parallel

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?

frog-leg wound

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

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

wye

A delta connected set of windings has a phase voltage of 480 V. What is the line voltage?

480 V