Transformers Chapter 3

Front 1

TRUE OR FALSE
Relatively large diameter conductors are used in electrical utility transmission systems. 

Back 1

FALSE

Hint 1

High voltages are used in transmission lines to reduce the required amount of current flow.

Front 2

What phase is used in the industrial customers?

Back 2

3 phase

Hint 2

it is more complex than residential

Front 3

Transmitting long distance electricity?

Back 3

using high voltages most efficiently.

Hint 3

High voltages are used in transmission lines to reduce the amount of current flow.

Front 4

true or false
The higher the level of the distribution voltage, the more difficult and expensive it becomes to between line wires, as well as from line wires to ground?

Back 4

TRUE

Front 5

TRUE OR FALSE
The unit substation is completely enclosed on all sides with sheet metal so that no live parts are exposed. 

Back 5

TRUE

Front 6

TRUE OR FALSE
The switchboard is usually supplied from the panel board

Back 6

FALSE

Hint 6

The panel board is supplied from the switchboard.

Front 7

PANEL BOARD def.

Back 7

Contains a group of circuit breaker of fuse protective devices for lighting, convenience receptacles, and power distribution branch circuits.

Hint 7

Referred to as the load centers.

Switchboards come after the panel boards.

Front 8

TRUE OR FALSE
A motor control center is a modular structure designed specifically for plug-in-type control units and motor control. 

Back 8

TRUE

Front 9

SWITCHBOARD

Back 9

A single panel or group of assembled panels with buses, over-current devices, and instruments.

Hint 9

This is the service entrance point when electricity enters the building

Front 10

TRUE OR FALSE
Movement of the coils within a transformer produces the transformation of voltage. 

Back 10

FALSE

Hint 10

AVERAGE EFFICIENCY IS 90% BECAUSE TRANSFORMERS HAVE NO MOVING PARTS.

Front 11

TRUE OR FALSE
Without transformers the widespread distribution of electrical power would be impractical.

Back 11

TRUE

Hint 11

Transformers doesn't change power levels between circuits.

Front 12

TRUE OR FALSE
For an ideal transformer, the power input is equal to the power output. 

Back 12

TRUE

Front 13

TRUE OR FALSE
Transformer power is rated in volt-amperes instead of watts.

Back 13

TRUE

Hint 13

Can only be operated in AC voltage because no voltage is induced if there is no change in the magnetic field.

Front 14

TRUE OR FALSE
The voltage ratio of a transformer is equal to its turns ratio. 

Back 14

TRUE

Front 15

TRUE OR FALSE
A step-up transformer is one in which the secondary winding current is greater than the primary winding current. 

Back 15

FALSE

Hint 15

If the primary has fewer turns than the secondary, you have a step-up transformer that increases the voltage.

Front 16

TRUE OR FALSE
If the secondary circuit of a transformer becomes overloaded, the primary circuit will not be affected. 

Back 16

FALSE

Front 17

TRUE OR FALSE
The low-voltage winding leads on a single-phase transformer are identified as H1 and H2. 

Back 17

FALSE

Front 18

TRUE OR FALSE
A transformer has subtractive polarity when terminal H1 is adjacent to terminal X1. 

Back 18

TRUE

Front 19

TRUE OR FALSE
When a 240/480 volt dual primary control transformer is to be operated from a 240 volt system the primary winding are connected in parallel. 

Back 19

TRUE

Hint 19

Parallel connection draws equal amounts of voltage.

Front 20

TRUE OR FALSE
In a Delta-connected transformer, the phase and line voltages are equal.

Back 20

TRUE

Front 21

TRUE OR FALSE
An autotransformer has electrical isolation between the primary and secondary circuits. 

Back 21

FALSE

Front 22

TRUE OR FALSE
Instrument transformers provide insulation between the instrument and the high voltage of the power circuit. 

Back 22

TRUE

Front 23

TRUE OR FALSE
A current transformer is a transformer that is designed to be connected in parallel with the circuit to be monitored.

Back 23

FALSE

Front 24

High voltages are used in transmission lines to reduce the transmission __________.  

Back 24

CURRENT (FLOW)

Front 25

Substations contain step-down _________ that reduce the voltage.

Back 25

TRANSFOMERS

Front 26

For a given amount of power delivered, doubling the transmission voltage cuts the electrical loses by _________.  

Back 26

75%

Front 27

Compared to the high voltage side, the low voltage side of a transformer draws _________ current.  

Back 27

MORE

Front 28

A unit substation of a building contains? 3 THINGS

Back 28

High-voltage switch gear 
Low-voltage distribution devices
Transformer

Front 29

When installing motors and motor controllers which of the following needs to be adhered to?  3 THINGS

Back 29

NEC
MANUFACTURERS' INSTRUCTIONS
STATE AND LOCAL CODES

Front 30

Conduit conductor capacity is generally based on a _______ fill ratio.  

Back 30

40%

Front 31

Conductors that deliver energy from the service equipment to the final branch circuit over-current device are known as

Back 31

Feeder conductors

Front 32

The transformer winding coil that delivers power to the load is known as the _________ coil winding.  

Back 32

Secondary

Front 33

The transformer winding coil that connects to the power supply is known as the _________ coil winding.  

Back 33

Primary

Front 34

The principle of operation of a transformer is based on ________ induction.  

Back 34

Mutual

Front 35

The __________ current sets up an alternating flux in the core of a transformer.  

Back 35

Exciting

Front 36

The efficiency of a transformer is typically in the _______ range.  

Back 36

90%

Front 37

When the secondary winding of a transformer is disconnected from the load,

Back 37

Very little current flows in the primary

Front 38

The low-voltage windings leads on a single-phase transformer are marked  

Back 38

X1 and X2

Front 39

What is the operating voltage of most commercial and industrial magnetic control systems?

Back 39

120 V

Front 40

Three-phase transformers are normally connected in_________ or _________.  

Back 40

 Wye, Delta

Front 41

The phase windings of a three-phase transformer are _______ electrical degrees apart.  

Back 41

120

Front 42

If the phase-to-neutral voltage is 120 volts in a Wye transformer system the phase-to-phase voltage would be  

Back 42

208 volts

Front 43

An auto-transformer motor starter reduces the starting current to the motor by

Back 43

Reducing the frequency of the applied voltage

Front 44

Compared to an equivalent traditional transformer the auto-transformer is  

Back 44

lighter and less costly

Front 45

The secondary low-voltage side of a potential instrument transformer is usually wound for  

Back 45

120 volts

Front 46

The secondary winding of a current transformer is designed to produce a standard current of

Back 46

5 A

Front 47

Potential transformers are used  

Back 47

with instruments and relays

Front 48

Current transformers are used to  

Back 48

supply a small amount of current that is proportional to the main current

Front 49

A control transformer is used to  

Back 49

reduce the voltage for motor control circuits.