ETUT 1160 Exam 4 sutdy

Alternator ________ is the process of connecting a three-phase alternator to another alternator or to a power grid. A) inversion B) conversion C) rectification D) synchronization

D

By convention, when the H1 lead of a transformer is instantaneously positive, the ________ lead is instantaneously positive A) H 2 B) X2 C) L2 D) X 1

D

The reduction of transformer efficiency due to copper loss is caused by A) flux linkage between the primary and secondary windings. B) lack cooling. C) hysteresis. D) resistance of the transformer windings

D

In a delta alternator connection, the line current has the same value as the phase current. TRUE or FALSE

F

It is safe to use a transformer rated for 60 Hz on a 50 Hz circuit. TRUE or FALSE

F

The device shown is a potential transformer. TRUE or FALSE

F

The high-voltage winding leads of a transformer are identified as X1 and X2. TRUE or FALSE

F

The nominal voltage rating of a transformer represents the maximum voltage that it is designed to operate at. TRUE or FALSE

F

Transformers may only be installed outdoors. TRUE or FALSE

F

In a three-phase connection, the current that flows in an externally connected voltage conductor is the line current. TRUE or FALSE

T

The phase sequence of a three-phase system may be reversed by interchanging the connections of any two of the three supply line wires. TRUE or FALSE

T

A delta-connected set of windings has a phase current of 10 A. The line current is: A) 17.3 A. B) 5.73 A. C) 10 A. D) 20.5 A. [NOTE: 1.73 (10)]

A

A transformer with more than one primary or secondary winding is called a ________-voltage transformer. A) dual B) split C) voltage D) current

A

For the 208/120 Volt three-phase four-wire system shown, the voltage supplied to the motor would be: A) ĭ208 Volts. B) ĭ120 Volts. C) ĭ120 Volts. D) ĭ208 Volts. [NOTE: 1.73 (120)(3)]

A

In a three-phase alternator connection, the voltage measured directly across one of the windings is the ________ voltage. A) phase B) delta C) wye D) line

A

Most transformers operate to transfer energy at an efficiency of about A) 80 percent. B) 95 percent. C) 25 percent. D) 75 percent.

B

A current transformer has its primary connection in A) a delta configuration. B) a wye configuration. C) series with the line. D) parallel with the line.

C

A standard oil dielectric test involves applying high voltage to a sample taken from the transformer and recording the ________ at which the oil breaks down. A) resistance B) volt-amps C) voltage D) current

C

The standardized secondary current rating of a current transformer is A) 25 A. B) 15 A. C) 5 A. D) 10 A

C