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1. Which of the following describes an autotransformer?

A transformer that is normally used with metering equipment when the line voltage is too high for the metering equipment

A transformer with two secondary windings that can deliver two secondary voltages

A transformer that has no electrical metallic connection between the primary and secondary windings

A transformer that uses a single winding for both its primary and secondary

Question 1 of 20

2. In a step-down transformer with a 4.16kV primary delta connection and a 480/277V wye secondary, the transformer turns ratio is ________.

15:1

5:1

11:1

9:1

Question 2 of 20

3. Which of the following refers to the total load seen by the CT secondary?

Current

Potential

Burden

Duty

Question 3 of 20

4. Which of the following systems is the most likely to be affected significantly by harmonics?

Three-phase, four-wire systems with no 120V loads

Three-phase, four-wire systems with nonlinear loads connected to 120V circuits

Three-phase, three-wire systems with no 120V loads

Single-phase, three-wire systems with some loads connected to 120V circuits

Question 4 of 20

5. Which of the following is defined as the ratio of the peak value of a waveform to the rms value?

Service factor

Eddy current

Frequency

Crest factor

Question 5 of 20

6. To select a buck-and-boost transformer use ________.

tables listed in the NEC®

standard electrical calculations

charts provided by the manufacturer

system measurements

Question 6 of 20

7. If the resonant frequency is near the harmonic voltage, the resultant harmonic current can ________.

increase the impedance

decrease the voltage

overheat the windings

blow the capacitor fuses

Question 7 of 20

8. A step-down transformer is a type of ________.

specialty transformer that is primarily used for small work, such as doorbells and other signaling systems

transformer that is considered a low kVA device

transformer that is usually connected to an electrical instrument, such as an ammeter, voltmeter, wattmeter, or relay

transformer that is connected in series with the load

Question 8 of 20

9. 15. The line voltages in a Y connection are ________.

lower than the phase voltages

the same as the phase voltages

1.812 times higher than the phase voltages

1.732 times higher than the phase voltages

Question 9 of 20

10. The instantaneous direction of current at a specific moment is known as ________.

hysteresis

impedance

internal resistance

polarity

Question 10 of 20

11. In a potential transformer, the voltage across the secondary terminals is always lower than the primary voltage and is rated at ________.

170V

150V

100V

120V

Question 11 of 20

12. Neutral overloading in a receptacle branch circuit may be detected by ________.

a reading of more than 2V to ground

a reading of more than 120V to the ungrounded conductor

a reading of less than 2V to ground

the load changing voltage across the circuit

Question 12 of 20

13. How many volts can a 1kVA buck-and-boost transformer actually carry in the secondary winding?

2.4kVA

1kVA

24kVA

11kVA

Question 13 of 20

14. Which of the following transformers is the most appropriate type of transformer to use for series street lighting?

Buck-and-boost transformer

Potential transformer

Constant-current transformer

Current transformer

Question 14 of 20

15. The frequency of the fourth harmonic is ________.

480

420

120

240

Question 15 of 20

16. Autotransformers are especially practical if the difference between the primary and secondary voltages is ________.

within 15% of factory specifications

relatively small

relatively large

as great as possible

Question 16 of 20

17. Potential or voltage transformers are ________.

buck-and-boost transformer

single-phase transformers

three-phase transformers

control transformers

Question 17 of 20

18. A device that is used to step up generated voltage to make it suitable for commercial transmission is called a ________.

potential transformer

power transformer

current transformer

grounding transformer

Question 18 of 20

19. The secondary current in a constant-current transformer is typically between ________.

0.5 and 1A

10A and 20A

4A and 7.5A

1A and 2A

Question 19 of 20

20. A residence with 120V and 240V loads is likely to be served by a(n) ________.

single-phase transformer with two secondaries

three-phase transformer

autotransformer

buck-and-boost transformer

Question 20 of 20

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