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Transformers > Chapter 3 > Flashcards

Chapter 3 Flashcards

Theory

1
Q

What is a transformer in its simplest form referred to as?

A

Nothing more than two coils of wire placed very close to each other (but not touching)

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2
Q

What happens if you place the two coils of wire around an iron core?

A

Induction will be maximized, and higher voltages will be obtained

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3
Q

What happens to a coil of wire that is placed next to another coil of wire that is attached to a source of AC Power?

A

It will become energized

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4
Q

How can the amount of induced voltage be transformed?

A

By changing the number of turns in the secondary coil.

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5
Q

What do transformers directly out of the generating station do?

A

Step-Up Voltage

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6
Q

What do transformers located at distribution substations and on distribution poles?

A

Step-Down Voltage

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7
Q

What is turns ratio?

A

A comparison of the number of turns of wire in each coil.

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8
Q

How is the turns ratio calculated?

A

By dividing the primary voltage rating by the secondary voltage rating

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9
Q

What is polarity?

A

The direction flow through the two coils.

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10
Q

Where is polarity set?

A

During the manufacturing process and cannot be changed in the field.

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11
Q

How is polarity determined?

A

By the direction the secondary coil is wrapped in relation to the direction the primary coil is wrapped

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12
Q

What can the polarity of a transformer be?

A

Additive or Subtractive

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13
Q

If it is additive, what side will the X1 Bushing be on?

A

Right-Hand Side

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14
Q

If it is subtractive, what side will the X1 Bushing be on?

A

Left-Hand Side

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15
Q

What is very important to know when banking and paralleling transformers?

A

Polarity

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16
Q

By industry standards, what will transformers 200kVA and smaller, with a primary rating of 8660 volts and below be rated?

A

Additive

17
Q

What will all other transformers be rated?

A

Subtractive

18
Q

What are the two main losses of the transformer?

A

Iron and Copper Losses

19
Q

What is an Iron Loss known as?

A

No-Load Loss and they’re created by the oscillation of the magnetic field in respect to the core

20
Q

What is a Copper Loss known as?

A

Load Loss caused when a current flows in a conductor

21
Q

What does heat limit?

A

Current flow and is referred to as I2R loss

22
Q

If a transformer didn’t have these two losses how efficient would it be?

A

100% Efficient

23
Q

What is impedance?

A

Total opposition to current flow caused by the transformer

24
Q

What is impedance made up of?

A

Resistance and Inductive Reactance

25
Q

Why is impedance important to lineworkers?

A

When transformers are to be banked or paralleled

26
Q

What must transformers impedance be within to bank or parallel them?

A

+/- 10% of each other

Transformers (7 decks)

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