Workbook Lesson 4

In a three phase circuit, the three windings are located within the generator to create three separate voltages which are out of phase with each other by ______ electrical degrees.

120

In a delta transformer how many degrees out of phase are the windings?

120 degrees c

A _______ winding is a third winding that is often used in power transmission to provide station power requirements or a tie with synchronous condensers.

Tertiary

In a wye to delta connection of three single phase transformers, one unit may be disconnected from the circuit and service maintained with the secondary operating in an open delta at _______ of normal bank capacity.

57.7

ANSI standardization rules that high-voltage leads brought outside the transformer case are to be marked with a ____ and low voltage leads are to be marked with a ____.

H/X

True or False: The majority of three phase transmission circuits in the U.S. are designed with three phase transformers connected to obtain three phase power.

False

True or False: The polarity of a transformer can be used to deduce the direction of the turns of the high and low voltage winding's around the transformer core.

False

True or False: A wye to delta connection may be made with three single phase transformers

True

True or False: In a delta transformer phase voltage and line voltage equal

True

True or False: Three phase transformers are seldom connected in a delta to delta connection.

True

True or False: Today, the majority of dwellings are wired with three-wire service

True

A(n) _______ connection may also be called a V-connection because only two sides on the delta triangle are included.

Open Delta

What delta type transformer connection may be utilized if only 2 transformers are available?

Open Delta

In a balanced three phase, delta connected system, the line current is equal to _____ times the current of one of the coils.

1.73

In a delta transformer the line current is equal to the winding current (phase current) multiplied by what factor?

1.73

The voltage tolerance on most motors is plus or minus ....

10%

Wye to delta connected transformers, with properly marked leads, always have an angular phase displacement of ...

30 degrees

In general, distribution transformers of 200kVA or less having voltages of 7500v or less have _____ polarity.

Additive

A wye(Y) system is also known as a _______ system?

Star

A(n) ______ connection is a three phase connection that has one end of each coil connected together and the other end of each coil left open for external connections.

Wye

What is a three-phase connection method that has the wire from the ends of each coil connected end to end to form a closed loop?

Delta Connection

True or False: In the secondary winding of a single phase transformer, the neutral wire generally carries a current equal to that of either of the two outside wires.

False.

In a wye connected system, the only current that flows in the neutral wire is the _____ current

Unbalanced