3B Last minute revision Flashcards
A transformer consists of
primary coil or winding, secondary coil or winding, a core
Transformer sich as 60 hz to 400hz require what?
core of low reluctance magnetic material
Why are core sheets laminated in transformers?
to dissipate heat more readily
What are the 2 types of transformers? and what is the most efficient
hollow core and shell core, the shell core is the most efficient
Why are wires coated in varnish on transformers?
insulate from every other turn/layer
Excitation current will flow in the primary coil at all times to maintain the magnetic field but,
No transfer of energy will take place to the secondary as long as the circuit is open.
If the primary circuit is hooked up to a source but the secondary circuit isnt what condition will exist in the primary circuit?
Excitation current
The total voltage induced into the secondary winding from the primary depends on?
ratio of the number of turns in the primary to the number of turns in the secondary and by the voltage applied to the primary
A transformer that has more voltage in the secondary than thew primary is said to be what?
step down transformer
When a load is connected to the secondary winding, current flow through the secondary coil creating a flux field with opposes the primary flux field, what law is this?
Lenz Law
What types of losses can you get in a transformer?
copper or I -squared R loss, eddy current, hysterisis, resulting in electrical energy into heat energy
How can the losses of a transformer be minimised?
lower resustance of primary and secondary wires (increase diameter), reducing the area of the core or by using super malloy or permalloy materials, Transformer cores are laminated to reduce eddy current loss.
What is one way of damaging a transformer?
Decreasing frequency, current through winding is increased resulting in heat damage.
How does the gcu monitor and regulate main generators output?
by controlling the amount of current that flows into the exciter field.
What happens when the GCU increases the amount of current flowing to the exciter field winding?
this increases exciter output, a higher exciter output increases the current flowing through the main generator field winding, there by increasing alternator output.
