2-2-7

According to this lesson, the U.S. standard for the polarity of single-phase transformers is ? for transformers below 200 kVA with high voltage ratings of 8,600 volts and below. Select one: a.additive b.negative c.positive d.subtractive

A. Additive

Distribution transformers are generally manufactured with ? polarity. Select one: a.additive b.negative c.positive d.subtractive

A. Additive

Indicate the polarity of the following transformer:7,200-volt, 15 kVA Select one: a.Additive b.Subtractive

A. Additive

When doing a polarity test, if the source voltage is 117 volts, and the transformer is subtractive with a ratio of 10:1, the voltmeter reading will be ? . Select one: a.101.8 b.105.3 c.112.2 d.115.8

B. 105.3

When doing a polarity test, if the source voltage is 117 volts and the transformer is additive with a ratio of 10:1, the voltmeter reading will be ? . Select one: a.120 b.128.7 c.135.5 d.146.6

B. 128.7

A polarity test should be performed on a transformer with a missing or damaged nameplate and the polarity marked on the transformer ? . Select one: a.bushing b.case c.coil d.hanger

B. Case

Indicate the polarity of the following transformer:13,800-volt, 75 kVA Select one: a.Additive b.Subtractive

B. Subtractive

Indicate the polarity of the following transformer:14,400-volt, 500 kVA Select one: a.Additive b.Subtractive

B. Subtractive

Indicate the polarity of the following transformer:4,160-volt, 333 kVA Select one: a.Additive b.Subtractive

B. Subtractive

Indicate the polarity of the following transformer:67,000-volt, 167 kVA Select one: a.Additive b.Subtractive

B. Subtractive

What voltage would be present at the primary bushings if 120 volts were applied to the secondary X1 and X3 bushings of a 2,400/4,160Y-120/240 transformer? Select one: a.120 V b.240 V c.1,200 V d.2,400 V

C. 1200 V

The H2 terminal on a single bushing transformer is solidly connected to the ? of the tank. Select one: a.bottom b.core c.inside d.top

C. Inside

The industry standard for the location of an H1 terminal when facing the ? is the left hand side. Select one: a.back of the transformer b.left hand side c.low voltage side d.right hand side

C. Low voltage side

Large power transformers are generally manufactured with ? polarity. Select one: a.additive b.negative c.positive d.subtractive

D. Subtractive

The direction the primary and secondary are wound on the core has nothing to do with polarity. Select one: True False

False

The ratio of the transformer does not matter when making a polarity test. The voltmeter will always show plus or minus 12 volts. Select one: True False

False

Current flows into a single-phase transformer in the H1 terminal and out the X1 terminal at the same instant. Select one: True False

True

It is critical to check polarity on older distribution transformers because it might be either additive or subtractive polarity. Select one: True False

True

Polarity is determined by the direction the high-voltage coil is wound in relation to the low-voltage coil winding direction. Select one: True False

True

The nameplate on a new distribution transformer shows the polarity of the transformer as it was manufactured. Select one: True False

True

The polarity of a distribution transformer can be changed by exchanging the internal leads on the secondary between X1 and X3. Select one: True False

True

According to U.S. standards, all transformers 200 kVA and above in all voltage classes and/or voltage ratings above ? are subtractive. Select one: a.8,600 V b.12,000 V c.12,500 V d.15,000 V

a.8,600 V

In order to phase in a single-phase transformer, the transformer ? . Select one: a.neutral must be connected b.polarities must be different on each one c.primary must be de-energized d.primary must be on a different phase

a.neutral must be connected