Unit 27 transformers
What is an isolation transformer?
There is no electrical connection between the primary and secondary windings because the secondary is isolated from the primary. It is magnetically coupled, no electrically. Reduces voltage spikes before they reach the load side.
what is a distribution transformer?
a type of isolation transformer. changes high voltage lines to 240/120v
what is a control transformer?
a type of isolation transformer. reduces line voltage
What are the 3 classifications of transformers?
isolation, auto, current
secondary winding?
load/output winding
what is mutual induction?
one coil induces voltage into another coil
primary winding?
power input winding
power in must equal
power out
What is an auto transformer?
primary and secondary share the same winding. can produce a small increase or decrease to line voltage. provides voltage regulation.
what do the transformer ratings include?
size, type, manufacturer, primary and secondary voltage, kva
What is excitation current?
the amount of current required to magnetize the core
What are the dots beside the terminal leads on a schematic?
the polarity of the windings
What is a transformer?
A magnetically operated machine that can change values of voltage, current, and impedance without a change of frequency
what are the efficiencies of an isolation transformer?
90-99
What is a step up transformer?
It has a higher secondary voltage than the primary
What is a step down transformer?
It has a lower secondary voltage than the primary
All values of a transformer are proportional to
Its turn ratio
One bad thing about an auto transformer?
No line isolation between the incoming power and the load
