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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.
Why is a transformer called constant flux machine?
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 primaryAs 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.
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.
How does a DC transformer work?
transformer cannot be worked on DC because as the dc is constant there will be no change of flux & may lead to shot circuit.
Why a double coil transformer does not work on a pure DC voltage source?
According to Faraday's Law only if there is change in flux linkage of a conductor then current is induced between mutual inductors. Now DC will induce a constant a constant flux in the transformer core, consequently in the secondary coil. So constant flux cannot induce a current in the secondary. SUBHRA JYOTI SAHA
Can you call any transformer as DC transformer?
No.it is not possible.as transformes action based upon induction principle it requirs varying flux.for dc the flux is constant.
Why does a 3 phase transformer produce an alternating flux while a 3 phase induction machine produces rotating flux when fed through 3 phase supply?
In a 3-ph transformer the flux also rotates round the 3 cores but you don't see anything moving.
With aid of diagram explain why magnetic flux of transformer remains almost constant from no-load to full load?
since the volt amphere turns in secondary neautralises the primary voltamphere turns making the magnetic flux in the core remain constant
Why transformer is not called a amplifier?
In transformers, it is the no.of turns of winding which is constant is use to merely step up or down voltage or current. The magnetic flux is linked with the coils due to current flowing through the coil and nothing more.Hence Transformer is a passive device.
Why transformer do not operate with DC?
Transformer works with varying flux. DC won't create it. Only AC produce varying flux.
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.
Which is the maximum efficiency machine between Alternator and Transformer?
the efficiency of transformer is more than alternator, because 1- the alternator have friction and windage loss but in transformer this not occure. 2- in the alternator the flux leak is more than the transformer, because in case of alternator the flux move through the air which is dimagnet and in transformer flux move through silicon steel. 3- in the other hand alternator have dc compound generator for exciation (depend on other electric course 220volt) but in t/f is not need.
In transformer core flux depends on voltage whereas leakage flux depends on current?
In a Transformer, Core flux is the difference of primary flux and Secondary flux which are opposite to each other in direction. There difference is equal to the no load flux at all loads. So, some of primary flux passes through the core and remaining becomes leakage flux (Because Secondary flux forces it to get out of the core). Same is the case with Secondary flux. Now, flux is directly proportional to Voltage and Current. When Current increases due to increased load (and voltage remains same): Then both primary and secondary flux increase. Because both of them increase, so there difference remains same. And all remaining flux is forced out. Hence leakage flux increases with current, but Core flux remains constant. When Primary Voltage is increased: Then only primary flux increases. So difference of this new increased primary flux and previous same secondary flux increases. Hence Core flux increases with voltage, But leakage flux does not. That's how In transformer core flux depends on voltage whereas leakage flux depends on current.
