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Power Transformer Leakage - dconant - 11-03-2025

Hello, I just finished splicing in new wire to a power transformer (Philco 45). The transformer is still out of the chassis. I did a continuity test on all leads to the core and got no readings. All AC reading are as expected but higher as expected being no load with power on the AC leads. Then I went and did something I have not done before having one meter lead on the 6 volt lead I then touched the other lead to the core and got about 40 volts using a DMM. I then did the same to all other leads except the primary ones. I get any where 40 to 150 volts. Since I never tried this before I don't know what to think. The core is in nice shape with no wax leaking. I checked my splices and found no shorts to the core. My leakage meter shows no leakage at all on the core with power applied. The transformer is plugged into and isolation transformer. Is this normal, if so where is this voltage coming from? I'm wondering if this is some kind of phantom voltage reading. Using a VTVM the most I get is 15 volts.

Dan

RE: Power Transformer Leakage - morzh - 11-04-2025

Put a ... 100K resistor between the core and the lead and see if the voltage goes down and how much.

RE: Power Transformer Leakage - Arran - 11-05-2025

I don't think that I have had a power transformer that had leakage to the iron core but I have found a few that had shorted turns in the H.V secondary and typically the transformer will start getting hot within 10 minutes, and almost immediately if it's really bad.
Regards
Arran

RE: Power Transformer Leakage - dconant - 11-05-2025

The voltage does not change one bit. After leaving connected for 15 minutes transformer is still room temperature.

462ron - 462ron - 11-06-2025

Dan, possibly that is stray voltage induced into the core, something you don’t see when the transformer is physically mounted to and grounded to the chassis, just a thought!

Ron

RE: Power Transformer Leakage - dconant - 11-06-2025

That is what I am thinking too. I tested another transformer out of chassis and get the same thing.

Dan

RE: Power Transformer Leakage - RodB - 11-06-2025

Stray voltage, isn't that called lightning? You guys are playing with the wrong power supply.

RE: Power Transformer Leakage - morzh - 11-06-2025

The voltages could be:

Stray
Feral
Wild