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

9:1

11:1

5:1

15:1

Question 1 of 20

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

Eddy current

Service factor

Crest factor

Frequency

Question 2 of 20

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

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

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

transformer that is considered a low kVA device

Question 3 of 20

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

increase the impedance

blow the capacitor fuses

decrease the voltage

overheat the windings

Question 4 of 20

5. 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 5 of 20

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

relatively large

as great as possible

relatively small

within 15% of factory specifications

Question 6 of 20

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

24kVA

11kVA

1kVA

2.4kVA

Question 7 of 20

8. Which of the following describes an autotransformer?

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

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

Question 8 of 20

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

tables listed in the NEC®

charts provided by the manufacturer

standard electrical calculations

system measurements

Question 9 of 20

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

120V

100V

150V

170V

Question 10 of 20

11. The frequency of the fourth harmonic is ________.

480

120

240

420

Question 11 of 20

12. Potential or voltage transformers are ________.

control transformers

buck-and-boost transformer

three-phase transformers

single-phase transformers

Question 12 of 20

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

1.732 times higher than the phase voltages

the same as the phase voltages

1.812 times higher than the phase voltages

lower than the phase voltages

Question 13 of 20

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

4A and 7.5A

1A and 2A

10A and 20A

0.5 and 1A

Question 14 of 20

15. 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 15 of 20

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

a reading of more than 2V to ground

the load changing voltage across the circuit

a reading of less than 2V to ground

a reading of more than 120V to the ungrounded conductor

Question 16 of 20

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

Potential transformer

Constant-current transformer

Current transformer

Buck-and-boost transformer

Question 17 of 20

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

Duty

Potential

Burden

Current

Question 18 of 20

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

hysteresis

impedance

polarity

internal resistance

Question 19 of 20

20. 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, three-wire systems with no 120V loads

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

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

Question 20 of 20

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