Question 1

When current transformers are used, the main power line is inserted through the opening in the transformer.

Accepted Answer

Current transformers are designed to measure the current in a power line and are mounted around the line without interrupting it. The opening in the transformer is used to clamp around the power line, not insert it through.

Question 2

The ____ type ammeter can have different range settings by changing the turns ratio of the secondary of the transformer.&#10;A) moving coil&#10;B) clamp-on&#10;C) moving iron&#10;D) zero-center

Accepted Answer

The clamp-on type ammeter can have its range settings adjusted by changing the turns ratio of the secondary of the transformer. This type of ammeter is designed to measure current without needing to disconnect the circuit being measured, making it versatile for different ranges.

Question 3

When a small amount of AC current must be measured, a CT is connected in the power line.

Accepted Answer

False

Question 4

To use the clamp-on type of AC ammeter, the jaw of the meter is clamped around all of the conductors supplying power to the load.

Accepted Answer

The clamp-on type of AC ammeter only needs to be clamped around one of the conductors supplying power to the load. It will still accurately measure the entire current flowing through all of the conductors.

Question 5

CTs have a standard secondary current rating of ____.&#10;A) 5 amps AC&#10;B) 10 amps AC&#10;C) 15 amps AC&#10;D) 50 amps AC

Accepted Answer

CTs (Current Transformers) typically have a standard secondary current rating of 5 amps AC to standardize the output for various monitoring devices.

Question 6

CTs are designed to operate with the secondary winding ____.&#10;A) at full load&#10;B) open&#10;C) shorted&#10;D) reversed

Accepted Answer

CTs (Current Transformers) are designed to operate with the secondary winding shorted to ensure accurate current measurement and to prevent dangerously high voltages that can occur if the secondary is open.

Question 7

A(n) ____ transformer is constructed with a hollow core similar to a donut in that it has a hole in the middle.&#10;A) current&#10;B) distribution&#10;C) toroid&#10;D) control

Accepted Answer

A toroid transformer is constructed with a toroidal (doughnut-shaped) core, which has a hole in the center through which the conductor passes. The toroidal core is made of a ferromagnetic material such as iron or ferrite, and it provides a high degree of magnetic coupling between the primary and secondary windings. This design reduces the leakage flux and provides a more efficient transfer of energy.

Question 8

Current transformers differ from voltage transformers in that the primary winding is generally part of the ____.&#10;A) core&#10;B) secondary winding&#10;C) shell&#10;D) power line

Accepted Answer

Current transformers have their primary winding integrated with the power line, allowing the transformer to measure the current flowing through the line by inducing a proportional current in its secondary winding. Voltage transformers, on the other hand, are connected across the line to measure voltage.

Question 9

The ability to change the turns ratio of a clamp-on ammeter can be very useful for measuring low currents.

Accepted Answer

By changing the turns ratio, the clamp-on ammeter can increase sensitivity and measure low currents accurately.

Question 10

The primary winding of a current transformer must be connected in parallel with the load.

Accepted Answer

The primary winding of a current transformer must be connected in series with the load.

Deck 21: Current Transformers