Transformers, Single Phase and Three Phase power calculations

A three phase transformer can be made from three single transformers wired in delta or wye configuration.

True

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

True

In a 240V high leg delta system, the voltage between the high leg and ground is 208V.

True

Using three individual transformers, to create a primary connection as wye, you would tie all the H1 terminal together and land power at H4. Do not worry about how H2 and H3 are jumpered for this question.

True

If power is applied to the transformer bank before the delta connection is closed, the voltmeter should indicate ____ volts.

0

Give a phase voltage and phase current, which formula below is correct for computing power

3∗Vph∗Iph∗PF

In an open delta configuration, the maximum output power will be:

86.6% of the total of two transformers

Primary Voltage: 7200 V Secondary Voltage: 240 V What is the turns ratio? Make sure to enter it as A:1 or 1:A

Correct Answer:30:1

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

False

In the three phase transformer, we transform lines, not phases.

False

Primary Current: 1000A Secondary Current: 100A Is this a step down transformer? Compute the turns ratio before you answer?

False

The following formula for calculating three phase power is correct: Power=3*Line Voltage * Line Current * Power Factor

False

When a power system is listed as 480/277 or 208/120, the system is wired as delta.

False

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

False

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. This is true whether a three-phase transformer is used or whether three single-phase transformers are employed to form a three-phase bank.

True

When wired in a delta with a center tap configuration (also called wild leg or hot leg delta), you can get 240V (line to line), 120V (line to center tap on two legs) and 208V (high leg to center tap) out of the same transformer.

True

You can create an open delta transformer using two transformers. All three phases will be present on the secondary side of the transformer.

True

You can run 120V single phase loads on a 208 wye system, if the neutral is installed.

True

You will get different power output of a three phase heater system if its wired delta as compared to wiring it wye, for the same line voltage.

True

In a wye system line current is:

equal to phase current

In a three phase delta, line voltage is:

equal to phase voltage

In a delta system line current is:

square root of 3 times phase current

In a three phase wye system, line voltage is:

square root of three times phase voltage