test 3 Flashcards
an ____ is any transformer in which the primary and secondary circuits have a portion of their two windings in common.
autotransformer
Why is lower impedance in an auto transformer a concern.
Higher current flow when a short circuit occurs
a buck-boost is typically used to change voltage between ___ and ___.
5% and 25%
Harmonics create problems by causing excess ____ in a transformer
heat
if the frequency is increased in parallel RC circuit the current will _____
increase
primary current of a 3-phase dry type transformer
KVA/(voltagex1.73)
what are three ways that guarding a transformer can be accomplished
enclosure
elevation
limit access
what are two functions served by the liquid in a liquid immersed transformer
dielectric
cooling
you are asked to select 3 transformers to supply a 135 KVA load which is connected. What size would you use
135/3
list two significant limitations of autotransformers
low impedance
lack of isolation between primary and secondary
there are 6 aspects of a transformer that should be checked when performing an internal inspection.
damage build up of dirt/dust core laminations coil taps windings hardware
_____ test of the insulating oil is a measure of the ability of the oil to withstand electric stress.
dielectric
what is the winding voltage of a single winding transformer connected delta to a 1200 volt line
1200V
what is the winding current of a transformer that is connected delta to a 50 AMP line
50/1.73
what would be the correct voltage between phases of the source voltage if you have a 3 phase wye connected transformer with primary windings rated at 35 kilovolts
35000x1.73
