Transformers Flashcards
what are transformers responsible for?
the production and control of high voltage - regulation and current
electromagnetic device that changes low voltage to high voltage or high voltage to low voltage without altering power in system
transformers
what principle do transformers work off of
electromagnetic mutual induction
which type of current do transformers need
alternating current
what does a simple transformer consist of
2 highly insulated coils lying side by side, a primary and secondary coil
explain simple transformer principle
primary coil supplied with AC, magnetic field that varies in direction and strength is set around the coil, changing magnetic flux cuts across the turns of the secondary coil which induces AC in secondary coil by mutual induction
transformer law
the EMF induced in the secondary coil is directly related to the amount of turns when compared to the primary coil
as the number of turns in the secondary coil increases,
the induced EMF increases
as the number of turns in the secondary coil decreases,
the EMF produced decreases
formula for transformer law
Vp / Vs = Np / Ns (V is voltage and N is number of turns)
step-up transformer
has more secondary windings, steps up voltage
step-down transformer
has less secondary windings, steps down voltage
if voltage increases in a transformer, what happens to current?
current decreases in order to maintain power in the system (P = V x I)
describe air core transformer
2 coils lying side by side, weak, loss of magnetic flux
loss of magnetic field at the ends of cores in transformers
Flux leakage
describe open core transformer
iron core within coils, more efficient than air core, intensifies magnetic flux, has flux leakage at ends of cores
describe closed core transformer
heavy insulated coils, continuous path for magnetic flux, donut shaped iron core with windings around core
describe core in closed core transformer
laminated silicon steel to reduce Eddy currents or loss of current
Eddy currents
loss of current due to the swirling effect of changing current and the changing of magnetic fields within the system
which type of transformer is most efficient?
shell type transformer
what is a shell type transformer made of
laminated silicon steel shell
describe construction of shell type transformer
primary windings are wrapped around secondary windings around a central core
formula for efficiency
E% = (power output / power input) x 100
efficiency is equal to
the ratio of power input to the power output
