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Haxby

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Joined: 07/07/2008
Location: Australia
Posts: 418

Posted: 04:57am 30 Sep 2021

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This is a question for Warpspeed but others might be interested in the reply so I'll post here:

I'm just revisiting the idea of running a warpverter style inverter with solar panels where the DC input is between 225 and 400 or so volts.

I understand that Warp tried this with only 3 transformers, with the 4th inverter being driven directly by the DC input voltage.

The problem with not using a 4th transformer on the largest inverter as I recall was that should the inverter fail, there may be a 225 to 400v DC output on the inverter, which can make AC appliances let all the smoke out.

Was that the only problem with this design?

If so, I would imagine a simple solution would be to monitor for DC on the output by having a contactor energised by a small transformer based power supply. Should DC saturate the small transformer, the contactor would lose power and just disconnect the load, thereby saving the loads that don't like DC.

Any thoughts on this?

Edited 2021-09-30 14:59 by Haxby

Warpspeed
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Joined: 09/08/2007
Location: Australia
Posts: 4406

Posted: 05:36am 30 Sep 2021

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Yes, you are quite right Phil.

It ran from voltage regulated +225v and -225v dc power rails, so it did not need the largest transformer. There was a half bridge circuit using a pair of IGBTs, and a second pair of series connected IGBTs to clamp the output to ground for the zero volt part of the cycle.

There were two things about it I did not like. The +/- 225v supply came from a switching power supply (that also performed the voltage regulation function) and that inherently limited the maximum power. It had no short term surge capacity beyond the full rated maximum continuous output.

That was all several years ago, when an early Warpverter ran from only one lookup table.
It has all come a long way since then. Multiple lookup tables solves the voltage regulation problem in a much nicer and more robust way.

And I discovered the hard way what happens if one of the IGBTs dies shorted. It puts +225v dc on the output, which immediately kills any motors or small transformers.
That mistake cost me very dearly, and its why I would not recommend it.

A big toroid hard switched direct from a big battery can have a massive short term surge capacity, and the transformer can only output ac. Its all as tough as nails, simple, and can be totally protected with a conventional C curve circuit breaker in the ac output.

Cheers, �Tony.

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