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Flashcards in Unit 22 Deck (26)
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1

What is used to reduce losses because of eddy currents in transformers? and what is used to separate them?

Long laminated iron cores ; insulation (usually lacquer)

2

The relationship of the primary winding voltage to the secondary winding voltage is the same as the relationship between the ________ on the primary as compared to the ________ on the secondary

Number of turns ; Number of turns

3

This device has the ability to transfer electrical energy from one system to another, with no physical connection between the two systems

Transformer

4

1 kilovolt-ampere = how many VA?

1,000

5

What do you call the energy required to realign the core molecules to the changing electromagnetic field in a transformer?

Hysteresis Loss

6

Conductor resistance is directly proportional to the ____ of a conductor and inversely proportional to the _____ of a conductor

Length ; Cross Sectional Area

7

The voltage level that can be induced in the secondary winding, form the primary magnetic field, is a function of the number of secondary conductor loops (turns) that are ____ by the primary electromagnetic field

Cut

8

What is the main purpose of an autotransformer?

Step voltage up or down

9

The energy transfer of a transformer is accomplished because the ______ lines of force from the primary winding induce a _____ in the secondary wnding

Electromagnetic ; Voltage

10

Autotransformers use a common _____ for both the primary and secondary.

Winding

11

The induced voltage in each loop of the secondary winding is dependent on the number of secondary conductor loops as compared to what?

The number of primary turns

12

The secondary winding of a step-down transformer has ____ turns than the primary winding.

Fewer

13

As current flows through the transformer, the iron core is temporarily ____ by the electromagnetic field created by the alternating current

Magnetized

14

The heating from harmonic currents is _______ to the square of the harmonic current

Proportional

15

The primary winding in a transformer is connected to the _____ and the secondary winding is connected to the _____

Voltage source ; Load

16

The disadvantage of an autotransformer is the lack of ____ between the primary and secondary conductors.

Isolation

17

Voltage induced in the secondary winding of a transformer is equal to the sum of what?

Voltages induced in each loop of the secondary winding

18

When a load is connected to the secondary of a transformer, secondary voltage induced from the primary magnetic field will cause _____ to flow through the secondary conductor wiinding

Current

19

Three-phase, 4-wire, wye-connected systems that supply nonlinear line-to-neutral loads can ______ because of circulating odd triplen ______ currents.

Overheat ; Harmonic

20

What is the formula for calculating a single-phase transformers primary and secondary current rating?

I = VA / E

21

The _____ lines from the secondary magnetic field effectively reduce the strength of the primary flux lines, and as a result, less CEMF is generated in the primary winding conductors.

Flux

22

The secondary current flow in the secondary winding creates an ______ field that opposes the primary electromagnetic field

Electromagnetic

23

Name four types of power losses that occur in transformers

Conductor Resistance ; Hysteresis ; Eddy Currents ; Flux Leakage

24

What is the formula for calculating a three-phase transformers primary and secondary current rating?

I = VA / (E x 1.732)

25

The leakage of the electromagnetic flux lines between the ____ and ____ also represents wasted energy

Primary ; Secondary

26

The secondary winding of a step-up transformer has ___ turns than the primary winding.

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