Coupling on Primary and Secondary Windings

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Denver Elliot

Why would a load on a secondary winding result in an increased current in a primary winding on certain transformers? Or, I guess, all transformers. ???

ron simpson

Put voltage on the primary of a transformer and a voltage appears on the secondary X turn ratio.
Current from a secondary must come from the primary. (turn ration)
Put a load on the secondary and the load appears on the primary. (turn ration involved)

A transformer is much like a electric motor turning a electric generator. Start out with 110 volts from the power line, that powers a motor that turns a shaft that turns a generator which makes 110 volts. ( or it could make 12 volts for your car) If you put a load on the generator (light bulb) the generator gets hard to turn. The motor must work hard. More power comes from the power line to run the motor. So turning on the light bulb (load) makes more current go into the motor.

Do you want to know about magnetic flux and such?

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Idina

I think understanding core magnetic flux is paramount to really understanding these sorts of topics.

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AndrewStenson

To me, the ideal transformer should act like a power coupler. Does that make sense?

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Dalearnoldson

I mean, as the load increases the secondary current increases and the currrent on primary increases. If that all makes sense.

An ideal transformer wouldn't create its own energy or lose it. It would have to deliver power to secondary same as the power on the primary.

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AndrewStenson

I see this may have changed to a new, but adjacent subject. But, the best-designed transformers, have small mutual inductance. You'll see more of the mutual inductance effect the poorer the transformer design.

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Denver Elliot

So what you are basically saying is Is↑ -> Ip↑ ?

I was actually looking for an explanation as to why it does that, the closest I have found is

the core magnetic flux is maximum under no load conditions and falls a little bit as the secondary is loaded.

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AndrewStenson

Yes, but the ampere-turns of the secondary due to the load are canceled by the ampere-turns increase on the primary due to that secondary load.