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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: LTSpice model for a SiC MOSFET
Date: Wed, 21 May 2025 03:34:16 +1000
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On 20/05/2025 7:58 pm, Liz Tuddenham wrote:
> Bill Sloman <bill.sloman@ieee.org> wrote:
> 
> [...]
>>> Capacitive divider using a spare core in the
>>> mains supply lead as one plate of the capacitor?  (Depending on supply
>>> frequency and required output current.)
>>
>> I can't see how that could work.
> 
> If you used a three-core mains lead with one of the cores connected to
> Neutral at the plug, one to Live at the plug and one floating, the
> floating lead would take up a potential somewhere between the other two,
> the stray capacitances between the leads acting as a capacitive divider.
> 
> The Live and Neutral leads are left unconnected at the equipment end and
> the floating lead is connected to a rectifier system which takes it's
> earth reference from the equipment being supplied.  It would be
> approximately a constant-current supply, so a capacitor and zener diode
> would be sufficient to stabilise it at the required low voltage.
> 
> The mains lead is acting as a high voltage capacitor but is a lot
> cheaper and more reliable.
> 
> If you need a solid earth on the output, use a four-core cable.

That's a lot of words but doesn't describe anything that takes a small 
direct current at high voltage and turns it into larger current at a low 
voltage.

"connected to a rectifier system" does suggest that you can envisage 
rectifier system that might do the trick but what is being asked for is 
its dual, an inverter system.

-- 
Bill Sloman, Sydney