P 23: xfmr Flashcards
Transformers permit the transfer of electricity between two circuits, which are
completely isolated form each other
In a transformer, the winding which receives the energy inductively is called
Secondary winding
A power transformer, transfers electrical power from one circuit at a certain frequency and voltage and to a secondary circuit…
At the same frequency, different voltage
True or False: Transformers are classified as static AC machines
True
A transformer developed 120 V in its secondary when a 2400 Volt source was connected across its primary assuming a primary .25 amperes the secondary current is
5 amps
When the number of turns or voltage on the secondary of a transformer is greater than that of the primary is known as a
Step up transformer
Transformers having only one winding are called
Autotransformers
The secondary of a potential transformer should never be
Short-circuited to remove the device it operates from service (because heavy current will burn the windings)
What is the induced secondary voltage of a transformer having a primary winding up 3000 turns in a secondary winding up 300 turns when connected to a 2400 VAC source
240V
In a core type transformer
A section of the primary and secondary windings are around each leg of the core
Current transformers are instrument transformers
used to
Step down current
Hysteresis can be explained as
Friction of the molecules due to alternating current
When a transformer windings are connected wye
The line current will be the same as the phase current
A series lighting system requires what type of transformer
A constant current transformer
The rating of a
transformer usually given in
- volt amps(VA)
- KVA
- MVA
- all of the above
All of the above
Bushings are used on transformers to
Serve as entrances into the transformer for the main leads
The conservator system is used on transformer to
Preserve the dielectric strength of the transformer oil
The secondary of a current transformer should never
be
Opened to remove the device it operates from service( high voltage danger)
True or false: In an energized transformer, iron losses are present, even if there is no load on secondary
True
In a transformer a _____ must always exist between the primary and the secondary field to maintain the required primary current to supply the transformer losses and secondary load
A balanced condition
