Transformer tripping breaker

schmitt trigger

Joined Jul 12, 2010
310
I suspect that the primary is wound with taps for different mains voltages.

Let's say, for the sake of illustration only, that the bottom-to-center is rated for Japanese mains voltages, which is 100 VAC.
The bottom-to-top is rated for North American voltages, 120 VAC.

Then from center-to-top the differential voltage can be only 20 VAC, before the transformer saturates.
If you apply 120 VAC, transformer saturation will appear as a near short and trip your breaker.
 

AlbertHall

Joined Jun 4, 2014
10,237
I suspect that the primary is wound with taps for different mains voltages.
Or as a step down for, say, a fan?

The primary resistance should be 0.43Ω which is tricky to measure with a standard multimeter. Connect the two probes together making sure to get a good contact and record the 'zero' reading. Then measure between the transformer terminals, again making sure to get good connections. The highest reading will be the terminals you want and if you subtract the 'zero' reading from the reading on those terminals it should be close to that 0.43Ω
 

Thread Starter

Hutch2793

Joined Jul 7, 2020
133
Nobody said lower current applications, lower "voltage" applications, that means the winding only has a few turns, and therefore a very low impedance.
I’m rewinding to get another center tap transformer that can supply 7 volts at 3 amps +, but I was concerned about these extra leads
 

Thread Starter

Hutch2793

Joined Jul 7, 2020
133
Does hooking a rectified transformer up to a hot water element and measuring the dc give accurate results since it is under load? I need a way to measure dc coming out of my transformers without oscilloscope.
 
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