Single Phase Power/ Three Phase Power

Question 1

What are X1, X2, and the center tap in this system?

Answer 1

X1= Line 1
X2= Line 2
Center Tap= Neutral

Question 2

What is the purpose of the neutral wire?

Answer 2

1. Regulates voltage for line one and line two
2. Carries unbalanced current between line one and line two

Question 3

Where does three phase power come from?

Answer 3

Fossil fuels
Nuclear
Hydro Electric
Solar/ Wind

Question 4

How many degrees out of phase with each other are the voltages of a three phase system?

Answer 4

120 degrees

Question 5

What colors are used to indicate three phase transformer power of 480/277 volts?

Answer 5

Brown
Orange
Yellow

Question 6

What colors are used to indicate three phase transformer power of 208/120 volts?

Answer 6

Black
Red
Blue

Question 7

What is an advantage of using a bank of three, single phase transformers over a single three phase transformer?

Answer 7

If one single phase transformer fails, it can be replaced

Question 8

In what system does line current=phase current?

Answer 8

A three phase WYE

Question 9

In what system does line voltage=phase voltage?

Answer 9

Three Phase Delta

Question 10

What are the eight things that need to be included on a transformer name plate?

Answer 10

1.) Name of manufacturer
2.) Rated KVA
3.). Frequency
4.) Primary and Secondary voltage
5.) Impedance of transformers 25 KVA and larger
6.) Required clearances for transformers with ventilating openings
7.) Amount and kind of insulating liquid where used
8.) For dry-type transformers, temperature class for the insulation system