49 Control Transformer

To avoid running separate lines to a machine for power devices and control devices, the higher voltage required by the power devices can be produced by using a control transformer to step up the control voltage.

True

False

False

When a control transformer is used, NEC requires that both sides of the secondary must be connected to earth ground.

True

False

False - 50V

Which of the following statements is true of a control transformer?

The supply lines are connected to the secondary.

The control circuit is connected to the secondary.

The control circuit is connected to the primary.

The control transformer does not isolate the control circuit from the power circuit.

B

Which of the following is not a component of a transformer?

Primary coil

Secondary coil

Electrical coupling

All of the above

None of the above

C

When checking a transformer with an ohmmeter, which of the following can you check for?

Coils shorted to the core

Opens in coils

Shorts between coils

All of the above

None of the above

D

Transformers are rated in units called Volt-Amperes (VA).

True

False

True

Which of the following allows you to control when the current will flow in a circuit?

Conductor

Power supply

Output device

Input device

D

Which of the following statements is not true of an electrical schematic?

An electrical schematic is a form of visual shorthand where each component is represented by a standard symbol.

Electrical schematics are helpful in troubleshooting a circuit.

An electrical schematic never shows electrical parameters such as voltage, current, or resistance.

An electrical schematic shows all components in a circuit and how they are connected.

C

The relationship between the input voltage and output voltage of a transformer is based on the __________.

Turns ratio

Core resistance

Wire resistance

Type of wire used

A

The output voltage of a transformer can be determined if you know the input voltage and the turns ratio.

True

False

True

The NEC requires that for an output voltage higher than 50 VAC one side of a control transformer secondary be connected to ground or both sides of the secondary must be fused.

True

False

True

To get a control voltage of 120 VAC from a dual-voltage control transformer if the line voltage is 480 VAC, the primaries must be connected in series.

True

False

True