transformer operation Flashcards
The principle by which a transformer induces voltage from one winding to another is known as ? .
electro magnetic induction
There will be no current present in a transformer unless there is a load connected to the secondary.
false
The process that limits current flow on the primary winding is self- ?
induction
AC windings will usually burn out if connected to a DC circuit.
true
The higher the number of turns on the secondary side, the lower the output voltage.
false
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.
true
Of the three ratios governing transformer operation, ? is in the reverse order to the other two.
current
The product of the primary voltage and current is equal to the product of the ?
secondary current and voltage
? is the number of turns in the primary winding to the number of turns in the secondary winding.
turns ratio
The voltage ratio of a transformer is the effective voltage of the primary to the potential voltage of the secondary.
false
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.
true
How can the primary turns of a distribution transformer be changed?
tap changing switch
A tap-changing mechanism works by adding in windings to the secondary side of a transformer.
false
When voltage is consistently ? , a company will, as a temporary measure, change the tap setting on the transformers, if the transformers are so equipped.
low
Distribution transformers have off-load tap switches, which do not in any way regulate the ? voltage.
secondary
Prior to changing taps, recording voltmeters should be set and left to record for at least ?
24 hrs
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%
An electric provider is allowed to have extreme voltages on a 120-volt service of 106 volts low and ? high.
127 v
A potential transformer is safe because it is not used to measure high voltage.
false
Current transformers reduce the current being metered to a value that should not exceed ?
5 amps
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
With the secondary open, if a CT is energized, the high voltage may puncture the insulation and cause injury to personnel.
true
Current transformers are installed on single-phase circuits when the current exceeds 400 amperes and on 3-phase circuits when the amperage exceeds ?
200A
With the use of CTs and PTs, conventional meters can be used to measure high current and high voltage circuits.
true
Michael Faraday discovered the principle of electromagnetic induction.
true
