Multiple-input transformer question

[jelliott]

I've got a transformer (part of a battery charger) that has five different inputs to provide five different charging rates.

My question is what would happen if 110 V mains power were to be simultaneously connected to two inputs at once?

(I've been assuming that the higher-rate inputs work by skipping windings on the primary coil to provide a lower transformation ratio, but I don't know a whole lot about AC circuits, and I don't want to risk the aforementioned failure mode without some confidence that it will be benign--or at least trip the circuit breaker that's on the higher-rate input before damaging anything.)

Thanks.

 

[crutschow]

If you connect two inputs at once, you will likely short circuit part of the winding. That will look like a short circuit load to the transformer and will either blow the transformer or the breaker, whichever is the weakest link.

 

[jelliott]

Related question about the same transformer: I can measure slightly different voltages on the unused inputs--if I have a resistive load that requires slightly higher voltage than what is being supplied to the transformer, can I power it from one of the unused inputs even though they're on the primary coil? What am I overlooking here?

Thanks again!

 

[dr pepper]

I dont know why you'd want to do that but yes you could, the unused taps would act as part of an auto transformer, if you have 0, 100,120,140v inputs and your power was connected to 0 and 120, then you could use 0 and 100 for a 100v supply, 0 and 140 for 14ov, 120 and 140 for a 20v and so on.
An autwound trans doesnt isolate the load from the supply, so the load needs to be trat as a live voltage load.

 

[Reloadron]

I've got a transformer (part of a battery charger) that has five different inputs to provide five different charging rates.

You are absolutely sure they are inputs and not output taps?

Ron

 

[tcmtech]

Typically battery chargers do the voltage tap changes on the primary side due to it having far less peak current levels to deal with in the switch.

 

[Reloadron]

Typically battery chargers do the voltage tap changes on the primary side due to it having far less peak current levels to deal with in the switch.

Good point as I never gave it much thought from that angle. Been looking too many old 6-12 volt automotive chargers.

Ron