I tested the transformer last night and found something I don't understand.
During the tests all secondary windings are not connected to anything but the multi-metre terminals.
Why there are such high, stable voltages on the secondaries against the ground point?
I don't think the capacitance between windings would create that sorts of voltages. I guess the multi-metre has about 1M input impedance... but not much more.
Regards,
Bill
An externally hosted image should be here but it was not working when we last tested it.
During the tests all secondary windings are not connected to anything but the multi-metre terminals.
Why there are such high, stable voltages on the secondaries against the ground point?
I don't think the capacitance between windings would create that sorts of voltages. I guess the multi-metre has about 1M input impedance... but not much more.
Regards,
Bill
Can't work out from your diagram where the 'ground point' is connected do you mean mains earth?
Most digital multimeters (I'm assuming that's what you are using) are quite high impedance devices and can play all sorts of tricks in high voltage circuits. When I was a tv repair person, we used analog avo 8 meters partly for that reason. A digital would sometimes 'find' a voltage at the end of an open circuit fuse, broken wire or burnt out component confusing us all somewhat.
Since you have 800v flying about, I'm not surprised by the odd readings. If you are worried try checking between the windings and transformer frame with an insulation tester (megger) - obviously mains must be disconnected for this and adequate precautions taken to avoid being zapped by the tester's output voltage.
Most digital multimeters (I'm assuming that's what you are using) are quite high impedance devices and can play all sorts of tricks in high voltage circuits. When I was a tv repair person, we used analog avo 8 meters partly for that reason. A digital would sometimes 'find' a voltage at the end of an open circuit fuse, broken wire or burnt out component confusing us all somewhat.
Since you have 800v flying about, I'm not surprised by the odd readings. If you are worried try checking between the windings and transformer frame with an insulation tester (megger) - obviously mains must be disconnected for this and adequate precautions taken to avoid being zapped by the tester's output voltage.
There is a fair amount of capacitance between the windings, maybe 100 pF or more. With the high impedance meter (10 megs), you'll measure voltage, but there's VERY little current available. Not enough to matter in-circuit, where there will be no voltage to speak of, due to much lower impedances.
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