Transformers are devices use for changing the voltages or currents of an A.C supply. The transformers may be used to increase or decrease theA.C (alternating current) supply. The transformers make use of the properties ofmutual inductance to change the voltage of the alternating current (A.C) supply.
Transformer may be used in homes to give a low voltage output from the main for our electronics gadgets like television, cassette recorder etc.
Transformer can also be used in power stations to produce very high voltages from national grid
Types of transformers
Thereare two types of transformers, step up transformer and step down transformer
Step up transformer: they are the transformers that are used to increase the voltage supplied, for examples the ones used in power stations
Step down transformer: These are the transformers used to decrease the voltages supplied, example, the ones `used in our electronics gadgets, like computer, television, music instrument and many others.
Primary and Secondary coil of transformer.
In transformer there are primary and secondary coils. The primary and secondary coils of transformers determine whether the transformer is step up or step down transformers. The coils can also be called primary and secondary wound
The coils which are laminated, are wound one on top of the
other to improve magnetic linkage. When A.C voltages are supplied to the primary
coils, it produces a change in magnetic filed within it. This change in
magnetic field links the secondary coils and therefore induces an E.M.f in it.
The magnitude of induced e.m.f (Vs) in secondary coil is related to the e.m.f (Vp) applied to
the primary coil by the equation below:
Where Vs=e.m.f induced in secondary coils, vp= e.m.f applied to primary
coils, Ns=the numbers of turns in secondary coil and Np = the number of
the turns in primary coils
Transformers that have Ns
> Np, they are the step up transformers but the ones that have Np > Ns, they the step down
If we assume that , there is no magnetic flux leakage , so that all the flux produced by primary coils link with the secondary and there is no energy losses also the ideal equation of transformers is given as
Ip and Is are the current flowing in primary
and secondary coils respectively
Efficiency of transformers
The efficiency of transformer is measured by ratio of out
put power to the input power. And is
given mathematically as E
Energy lose in
transformers and how to reduce it
1. Edddy current loses in the core, which can be reduces by
laminating the core.
2. Hysteresis loss, this is energy lost due to heating as
magnetic domains in core realign. It can be reduced by using soft magnetic
material for core, example silicon-iron.
3.Flux Leakage: it is reduced by having efficient core
design (soft iron core) to ensure that all the primary flux is linked with
4. Energy lost due to heating in the coils. This can be
reduced by keeping their resistance low.
A transformer which can produce 12V from 240r.m.s supply has efficiency of 80%. If the current in the secondary coil is 10A, calculate the current in the primary coil.
The HTML Clipboard
where VS= 12V, IS =10A, Vp =220V Efficiency = 80%, and IP =?
17600IP = 12000
Use of transformers
1. Transformer is used in production of our electronics,
gadgets, to step down the current from the supply.
2. Transformer, is used in power generating station to step
up the current