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when a load is connected to a transformer current(say I2) flows through secondary coil thus an M.M.F (N2I2) is produced ,this produces the secondary flux.
This flux reduces the the main flux induced in the primary & also reduces E.M.F E1 in the primary
As a result more current is drawn from the supply. This additional current drawn is due to the load component(say I2' )
This I2' is anti-phase with I2.This I2' sets a flux which opposes the secondary flux & helps the main flux.
The load component flux neutralises the secondary flux produced by I2 .The M.M.F N1I2' balances N2I2.Thus the net flux is always at constant level.
As practically flux is constant,the core loss is constant for all loads.
Hence a transformer is always called a Constant Flux Machine.
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Is mutual flux in transformer constant for all loads?
The flux is set by the voltage applied to the transformer. In most applications, the voltage is constant, and therefore the flux is constant also.
What are the differences between the natures of dc flux and ac flux?
dc flux is caused by dc current (flux and current are proportional), it is a constant value. Put an inductor (or transformer winding) across a battery and you will get dc flux. ac flux is caused by ac current (flux and current are proportional), it is a moving value, the flux moves with the current, typically cyclical but the waveform is arbitrary as long as we're moving.
Does the flux changes due to change in the load in a transformer?
Yes, the two things that chage the number of flux lines in a transformer(electromagnet) are the number of turns in the windings and the amount of current flow
What is the difference between ideal transformer and practical transformer?
There are basically 4 major differences :- 1. The windings (both primary and secondary) of an ideal transformer are considered to have zero resistance, hence the transformer is lossless. 2. There is no leakage flux in an ideal transformer. 3. The permiability of the core material in ideal transformer is considered to be tending to infinity and hence the current needed to set up the flux in the transformer is negligible. 4. There is zero hysterisis and eddy current losses in an ideal transformer.
Is direct electric current used in transformers?
no direct current is not used in transformers. the reason is that, if dc is used, there would be no counter emf to oppose it in the primary winding. since the constant flux will be flowing in the dc, there would be no rate of change of flux. as a result, the total current will be applied at the primary winding only. this results in the burning of the total primary winding. ===================================== The practical application is: If transformer input is DC, transformer output is smoke.
