Deck 15: Single-Phase Transformers

Question 1

Transformers with only one winding are called ____________________.

Answer 1

autotransformers

Question 2

Regulation of constant potential transformers is about 10-25% at the secondary terminals.

Answer 2

False

Question 3

A 460/115/230 transformer may be connected for two ratios: 460/115 or 230/115.

Answer 3

False

Question 4

For subtractive polarity, the voltmeter reading (V) is less than the applied voltage.

Question 5

A(n) ____________________ transformer is designed with a metallic shield between the primary and secondary windings, providing a safety factor by grounding.

Question 6

How must the two secondary coils of a 460/115/230-volt, single-phase transformer be connected to obtain 460/115 volts?

Question 7

What is regulation and what is it caused by?

Question 8

How are dry transformers cooled and what are they used for?

Question 9

Single-phase distribution transformers can be connected in parallel only if the voltage and ____________________ ratings of the transformer are identical.

Question 10

If the voltage fluctuates consistently, tap changing is not the solution. A(n) ____________________ transformer is needed.

Question 11

What is the significance of the H and X terminals in a transformer?

Question 12

In conventional usage, ____________________ refers to the induced voltage vector relationships of the transformer leads as they are brought outside of the tank.

Question 13

What type of transformer does the NEC require in all distribution circuits except those circuits assigned to autotransformers?

Question 14

If a 460/115/230-volt, single-phase transformer is to be connected to obtain 460/230 volts, the two secondary coils must be connected in parallel.

Question 15

Taps are arranged in increments of 2.5% or 5% of the primary nominal voltage rating of the transformer.