Don't read this as gospel, just thoughts.
Is there a dual secondary?
You could wire it up like a site 110Vac transformer.
The centre tap is earth and the two windings are at 55Vac either side of that centre tap.
It's the same way that North America brings their 220/240Vac into their houses.
Two 110/120Vac either side of Neutral.
Is there a dual secondary?
You could wire it up like a site 110Vac transformer.
The centre tap is earth and the two windings are at 55Vac either side of that centre tap.
It's the same way that North America brings their 220/240Vac into their houses.
Two 110/120Vac either side of Neutral.
That 40Vac you have measured is due to the way you have tested that set up.
If you connect a 1M0 resistor from that centre tap to earth you can measure the current flowing from centre tap.
You will discover something.
Either you wired the test set up incorrectly or that the current is in the sub µA range
If you connect a 1M0 resistor from that centre tap to earth you can measure the current flowing from centre tap.
You will discover something.
Either you wired the test set up incorrectly or that the current is in the sub µA range
Well. The measured inducted current between PE and secondary CT was as you expected some 40 uA. Putting a Hammond 155 H, 5 H 50 mA with a DCR of some 250 ohm in between them braught it down to around 2 VAC. I can probably put a 150 H 8 mA 156C with a DCR of 3700 ohm and still get a controllable reference and it will shut out evil stuff from the mains PE to my testbench.
Thing is, do I want to do this? What happens when I short something on the bench? Is that 40 V 40 uA a problem at all? Theres probably electrical engineers around that can answer this.
Thing is, do I want to do this? What happens when I short something on the bench? Is that 40 V 40 uA a problem at all? Theres probably electrical engineers around that can answer this.
I am very surprised that the same 40Vac is maintained across the 1M0 resistance to pass that 40uAac.
I expected it to fall massively since I thought the voltage was due to capacitive coupling.
I wonder if it is worth trying 100k instead.
Check how you have wired it into the Mains.
unloaded VOLTAGE is 40Vac.
It's similar for all isolated windings. One can get numerous spurious winding voltages and that is normal.
But when one makes a reference link, one discovers that the Power available is tiny.
i.e. when you draw a little bit of current the available voltage is low.
draw a bit more current and the available voltage is tiny.
I suppose that is the effect of the very high source impedance of the capacitive coupling. High emf and high Rs = very low output power.
A transformer expert will probably say my layman's explanation is completely misleading, but none have come forward to give a scientific explanation.
It's similar for all isolated windings. One can get numerous spurious winding voltages and that is normal.
But when one makes a reference link, one discovers that the Power available is tiny.
i.e. when you draw a little bit of current the available voltage is low.
draw a bit more current and the available voltage is tiny.
I suppose that is the effect of the very high source impedance of the capacitive coupling. High emf and high Rs = very low output power.
A transformer expert will probably say my layman's explanation is completely misleading, but none have come forward to give a scientific explanation.
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