Unit 8

When three single phase transformers are used to make a three phase transformer bank, their primary windings are always connected in a ways connection.

False

If power is applied to the transformer bank before the delta connection is closed the voltmeter should indicate how many volts?

0

The primary windings of three single phase transformers have been connected to form a wye connection. The phase voltage is less than the line voltage by a factor of what?

1.732

The Scott connection is used to convert three phase power into one phase power using three single phase transformers

False

In a delta connection, the phase and line voltage are the same

True

A connection involving the use of two transformers to supply three phase power is the T-connection: in this connection, one transformer is generally referred to as the be main transformer and other is the

Teaser transformer

A three phase transformer is constructed by winding three single phase transformers on a single core

True

The open delta transformer connection is often used when the amount of three phase power is needed is not excessive, such as in a small business

True

When three phase transformers are connected as a wye or delta, the primary and secondary windings themselves become the phases of a three phase connection

True

A dielectric oil provides electrical insulation between the windings and the

Case

One of the most common three phase to six phase connections is the

Diametrical connection

In a three phase wye transformer, the phase value of the primary voltage can be computed using the formula Ep(primary) =

El/1.732

Three single phase transformers are connected to form a wye delta bank. Once the voltage across each of the load resistors are known, the current flow through the phase of the load can be computed using the formula Ip(load) =

Ep(load)/R

What phase values can be used when computing transformer values?

Voltage and current

What kind of diagram illustrates a delta-wye connection and is generally used to show the main power distribution system of a large industrial plant?

One line

If three phase transformation is needed and a three phase transformer of the proper size and turns ratio is not available, three single phase transformers can be connected to form a

Three phase bank

A voltmeter is a low impedance device

False

Three phase transformer connected in a delta delta configuration. The load is connected as a ways and each phase has an impedance of 7 ohms. The primary is connected to a line voltage of 4160 V and the secondary line has 440 V. The turns ratio must be 9:45:1

True

A wye-delta transformer has its primary winding connected in a delta and its secondary winding connected in a wye

False

Delta connections should only be checked for proper polarity after making the final connection and applying power.

False