Delmar's Electricity unit 27

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

120 degrees

The horsepower rating of a 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

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

3

Line voltage in phase voltage are the same in the ----- connection

Delta

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

I line=Iphase x 1.732 ....17.32A

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

The square root of 3. (1. 732)

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

In a three phase circuit the true power ( watts) is found by

Multiplying apparent power by the power factor P=sq Root of 3 xE line x I line x PF. Or P=3 x E phase x I phase x PF

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

Never falls to Zero

Line current and phase current are the same in the -----configuration

Wye

The three phase connection in which one end of each of the windings are connected together is called a ---connection

Wye