2-6 quiz

An electric provider is allowed to have extreme voltages on a 120 volt service of 106 volts low and ___?___ high

127 Volts

A transformer with 14,400 primary turns and 500 secondary turns produces a secondary voltage of 480 volts assuming 100% transformer efficiency the primary voltage is

13,824 volts

Current transformers are installed on single phase circuits when the current exceeds 400 amperes on a 3 phase circuit when the amperage exceeds

200 Amp

The transformer ratio is 10:1 if the secondary voltage is 210 volts the primary voltage is

2100 Volts

Prior to changing taps recording voltmeter should be set and left to record for atleast

24 hours

Recording voltmeters should be set at the customer's service entrance because there may be a __?__ drop in voltage between the transformer and the customer's service entrance

4 %

Current transformers reduce the current being metered to a value that should not exceed

5 Amp

Given: a primary voltage of 2,292. To maintain a secondary voltage of 240 volts, the tap changer should be set to 4.5%, which means that __?__ of the primary windings are in use.

95.5%

Of the three ratios governing transformer operation __?__ is in the reverse order to the other two

Current

A potential transformer is safe because it is not used to measure high voltage (T/F)

False

A tap-changing mechanism works by adding in windings to the secondary side of a transformer. (T/F)

False

The higher the number of turns on the secondary side the lower the output voltage (T/F)

False

The voltage ratio of a transformer is the effective voltage of the primary to the potential voltage of the secondary (T/F)

False

There will be no current present in a transformer unless there is a load connected to the secondary (T/F)

False

When voltage is consistently ___?___ a company will as a temporary measure change the tap setting on the transformer if the transformer are so equipped

Low

The windings that receives the energy is the ___?___ windings

Primary

A current transformer should have its ___?___ short circuited while being installed or while connected in a circuit with no meter connected to the secondary

Secondary

Distibution transformers have off load tap switches which do not in any way regulate the ___?___ voltage

Secondary

AC windings will usually burn out if connected to a DC circuit (T/F)

True

If the turns ratio is shown as 10:1 it is a step down transformer if the ratio is shown as 1:10 it is a step up transformer (T/F)

True

Michael Faraday discovered the principle of electromagnetic induction (T/F)

True

The voltage change from primary to secondary is governed by the ratio of turns in the primary coil to the turns in the secondary coil (T/F)

True

With the secondary open if a CT is energized the high voltage may puncture the insulation and cause injury to personnel (T/F)

True

With the use of CT's and PT's, conventional meters can be used to measure high current and high voltage circuits. (T/F)

True

___?___ is the number of turns in the primary windings to the number of truns in the secondary windings

Turns ratio

How can the primary turns of a distribution transformer be changed

With a tap changing switch

The principle by which a transformer induces voltage from one winding to another is know as

electro magnetic induction

The process that limits current flow on the primary windings is self-______?

induction

The product of the primary voltage and current is equal to the product of the

secondary current voltage