Flashcards in Transformers & PCB's Deck (50)

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1

## Made by connecting one end of each winding.

### Wye connection

2

## Line and phase ____ are the same in a wye connection.

### Currents

3

## In a wye-connected system, the line voltage is higher/lower than the phase voltage by 1.732.

### Higher

4

## Three-phase voltages are ____ degrees out of phase with each other.

### 120

5

## Delta connections are made by ____ separate inductive loads being connected.

### 3

6

## T/F In a delta connection, line and phase voltages are different.

### F, they are the same.

7

## T/F In a delta connected system, the line current is lower than the phase current by 1.732.

### F, higher

8

## If line values of voltage (E) and current (I) are known, apparent power is calculated by:

### VA = 1.732 x E (line) x I (line)

9

## If phase values of voltage (E) and current (I) are known, apparent power is calculated by:

### VA = 3 x E (phase) x I (phase)

10

## Three phase watts (P) is calculated by:

###
P = 1.732 x E (line) x I (line) x PF

(PF = 1 unless otherwise stated)

P = 3 x E (phase) x I (phase) x PF

(PF = 1 unless otherwise stated)

11

## T/F Wye connections are characterized by the fact that 1 terminal of each of the devices is connected together.

### T

12

## What is a magnetically operated machine that can change values of voltage, current and impedance without a change of frequency?

### Transformer

13

## What are the 3 transformer classifications?

###
isolation transformer

autotransformer

current transformer

14

## Are all values of a transformer proportional to its turns ratio?

### Yes

15

## Turns ratio example:

### 4:1 means 4 turns of primary winds to 1 secondary wind

16

## N(P)

### # of turns in primary winding

17

## N(S)

### # of turns in secondary winding

18

## E(P)

### Primary voltage

19

## E(S)

### Secondary voltage

20

## I(P)

### Primary current

21

## I(S)

### Secondary current

22

## Transformer formulas

###
EP/ES = NP/NS

EP/ES = IS/IP

23

## Where is the power input winding connected to incoming power supply (generator side)?

### Primary winding

24

## Where is the load or output winding connected to driven load?

### Secondary winding

25

## T/F In an isolation transformer, the secondary winding is physically and electrically isolated from primary winding.

### T

26

## What is it called when a coil induced a voltage into itself?

### Self-induction

27

## The ____ current is the amount of current required to magnetize the core of the transformer.

### Excitation

28

## T/F Mutual induction is the ability of two coils to induce a voltage into another coil.

### F, one

29

## What is a step-down transformer?

### A transformer that has a lower secondary voltage than primary.

30