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Why aren't isolation transformers widely used?

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Could anyone give me some reasons why isolation transformers are not widely used for protection in sockets of home installations?

I know that one possible reason is the extra cost. Anyone has any idea how much bigger that cost is e.g. per socket?

Any other reasons for not using them?

Thnx a lot in advance!

K.
 

Size does also matters.

Nandhu
 

isolation transformers are not used in places where the switching off at times happens... well u know how we use the socket....
 

Here the reasons:
1) Weight
2) Cost
3) Noise
4) Consumption
5) Dimensions
6) Ground connection

After all:
a) If you not have a good ground connection the transformer is mostly useless because the capacitive coupling between the windings leave pass all the high frequency part of the strike;
b) the transformer must be dimensioned for the maximum load due the contract with the electric company, but at home usually the contract is not fully used except for some peaks during the day; the transforme anyway dissipates a good 5% of the rated power in heat and this could be a significative part of the daily average power used.
c) If placed in the wrong environment the life of the transformer is usually very short

Mandi
 

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    kgl_13gr

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FANT said:
Here the reasons:
1) Weight
2) Cost
3) Noise
4) Consumption
5) Dimensions
6) Ground connection

After all:
a) If you not have a good ground connection the transformer is mostly useless because the capacitive coupling between the windings leave pass all the high frequency part of the strike;
b) the transformer must be dimensioned for the maximum load due the contract with the electric company, but at home usually the contract is not fully used except for some peaks during the day; the transforme anyway dissipates a good 5% of the rated power in heat and this could be a significative part of the daily average power used.
c) If placed in the wrong environment the life of the transformer is usually very short

Mandi
Click to expand...

you have mentioned capacitive coupling between the windings... isnt it inductive coupling between the windings in case of transformer....

talking about noise the transformer has to be properly shielded or a kickstart of a vehicle somewhere nearby could cause a spike enough to damage the transformer.....
 

I think Anand, a high spike cannot damage the isolation transformer. It is high voltage, if persist for an appreciable time (a spike can only last for less than a second, othewise it is not a spike) can damage. Or overload can damage, again if connected for an appreciable time.
 

inductor depend on di/dt and the shorter the spike the more dangerous it is to the transformer.... i mean if the spike lasts only for a few microseconds if it gets coupled then the dt term is very small and hence the voltage reached would be very high....
 

Terribly low PF and a correction needed.
 

Sorry for the delay of the answer, but I was on holidays.
The coupling for the power is really an inductive coupling, and thisi is that carries the power, but in high frequency the high inductance makes the reactive part very high and then there is no power transfer.
A side effect is that the windings are one in front of te other and this resembles a capacitor; in low frequency the effect is negligible ( ie 50/60 Hz ), but in high frequency as is the fourier transform of the lightning the reactive capacitance is very low and then a quite big amount of energy passes for the capacitive coupling and not for the inductive coupling.
Mandi
 

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