EEM 218 Chp.28 and 29

A wye connected secondary has a phase voltage of 277.14V What is the line voltage.

480V

A Transformer has a 240v primary and a 120v secondary. With a 30ohm load connected, what is the primary volt-amps.

480VA

A wye-delta transformer has a turn ration of 2:1. It has a secondary line voltage of 480v. The secondary is connected to a wye-connected three-phase resistive load of 50 Ohms in each phase. How much current flow is there in each load resistor?

5.54A

A delta-delta transformer has a primary voltage of 7200 V and a secondary voltage of 360 V. What is the turns ratio?

20:1

Dielectric oil performs which of the following functions?

Electrical insulation between the windings, case cooling, and prevent formation of moisture.

In a transformer, even when there is no load connected, there will be some small current flow known as _______ current.

Excitation

Most transformers cares are not made from a solid piece of metal. Instead, they are assembled from many thin sheets of metal. This type of construction is called ________ _________.

Laminated Core

In three-phase transformer connections, the primary leads are labeled with the letter _____ and the secondary leads are labeled with the letter ____

H, X

An Isolation transformer has the same input and output voltages. (T or F)

True

In a transformer, the turns of primary wire compounded to the turns of secondary wire is called the __________ ratio.

Turn

A transformer in which secondary voltage is less than the primary voltage is called a ________ _______ transformer.

step down

A transformer in which the secondary voltage is more than the primary voltage is called a ______ _______ transformer.

step up

A delta-wye transformer has its ______ ______ connect as a delta and its _______ ________ connected as a wye.

Primary winding, secondary winding

Any transformer flux that does not follow the core and escapes into the surrounding air is called ________

Leakage

A wye-delta transformer has a primary voltage of 7200 V and a secondary voltage of 360 V. What is the turns ratio?

20:1

An open delat transformers is assembled from two 50KVA transformers. The output power of the open delta is

86.6KVA

When using an open delta with a center tapped transformer, one wire is the high leg. The high leg is the one that _________________________________________.

the voltage is higher than the other 2 conductors.

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

3 phase bank

A wye-delta transformer has a turn ration of 2:1. It has a secondary line voltage of 480v. The secondary is connected to a wye-connected three-phase resistive load of 50 Ohms in each phase. How much is the primary line current.

1.6A

A wye-delta transformer has a turn ration of 2:1. It has a secondary line voltage of 480v. The secondary is connected to a wye-connected three-phase resistive load of 50 Ohms in each phase. How much is the primary phase current.

1.6A

An open delta connection is made using _______ single-phase transformers.

2

An open delta transformer is assembled from two 150 KVA transformers. The output power of the open delta is

259.8KVA

A transformer has a 240v primary and a 60v secondary. With a 5 ohm load connected, what is the primary volt-amps?

3A

A transformer has a 2:1 turns ration. 120v is applied to the primary. What is the secondary voltage?

60v

A delta wye transformer has a turn ration of 9;1. the primary line voltage is 3600v. what is the secondary line voltage.

696.82v

a wye-delta transformer had a primary line voltage of 7200 V and a secondary line voltage of 480V. What is the turns ratio?

8.66:1

A transformer that has one winding, which is used for both the primary and secondary, is called a _______ __________.

Auto Transformer

The industrial use transformer that normally has 240 V or 480 V primary and a 120 V secondary is called a _________ transformer.

Control

When single-phase loads are tied to a three-phase transformer, the phase currents of the transformer will be automatically balanced. (T or F)

False

A transformer in which the primary and secondary are physically separated and not connected by a conductor is called a ________ transformer.

Isolation

A transformer supplying a house with 240/120 V has a secondary winding which is center tapped. The conductor connected to the center is called the ______ conductor.

Neutral

The transformer winding, which is the power input winding, is called the ________ winding.

Primary

A _____ ______ diagram is generally used to show the main power distribution system of a large industrial plant.

One Line

In an open delta with single-phase loads, the high leg must be identified by

Orange wire, or tagging it at only point where a connection is made if the neutral conductor is also present.

The transformer winding, which is the output winding, is called the __________ winding.

Secondary

The _______ ________ transformer is constructed in a similar manner to the core type, except that the shell type has a metal core piece through the middle of the window.

Shell Type

The magnetically operated device that can change values of voltages, current, and impedance without changing frequency is the ____________.

Transformer

In an open delta with a center-tapped transformer, label the two ends of the center tapped transformer as L2 and L3 and label the high leg as L1. The current flow in the neutral is equal to ___________________

increasing the center tap voltage by 1.732 or AN= A1 + (A2-A3)

A Tape wound core is assembled by

tightly winding 1 long continuous silicon steel tape into a spiral.

A tape wound core is also called a ________ core.

toroid

When connecting three transformers for three-phase use with a delta secondary, a voltage test should be done before closing the secondary. The correct voltage reading is ___ volts.

0

A wye-delta transformer has a turn ration of 2:1. It has a secondary line voltage of 480v. The secondary is connected to a wye-connected three-phase resistive load of 50 Ohms in each phase. How much is the secondary phase current.

3.2A

A wye-delat transformer has a secondary phase voltage of 480V. A delta-connected resistive load has a resistance of 12 ohms in each leg. what is the current in each load leg?

40A

The transformer that converts high voltage from the power company down to 240/120 V for homes and businesses is called a _________ transformer.

Distribution

The amount of current that flows into a transformer primary when voltage is first applied is called ________ current.

Inrush

A wye-delta transformer has its ______ ________ connected as a wye and its ______ _________ connected as a delta.

Primary winding, Secondary winding

For installations that will have both three-phase and single-phase loads on a three-phase transformer, the utility company often provides ____ ________ ______ ______ ______ ______ _____ three-phase transformer.

open delta with transformer center tapped