Re: Another 3 phase issue

Andrew Mawson wrote:



I've got a ginormous brand new three phase motor if anyone wants to
play with REAL power. 15 kW iirc so that's 20 HP - it weighs 70 kgs
and is a lovely bit of kit. I got is to make a huge three phase rotary
converter, but never did, and now I'm moving it needs to go ! To go
with it to make the three phase rotary converter I also have one of
the ex Peter Forbes whopping big 240 - 110 isolating transformers that
with a bit of simple re-jigging can be used as a 240 to 415v auto
transformer to generate genuine 3 phase 415 v from single phase mains.
email me if interested

AWEM



Am new to this group, but this may be usefull: Recently built a 500v 10a ish dc psu to drive 3 phase input inverters. (They are much cheaper) If you try to drive them across two phases with a 110v transformer in series with the mains, most complain about phase loss, but internally they are just a rectifier driving an inverter, so if you run them from DC, they work fine.

The psu is just a 10a 110v isolation tranformer, in series with the mains, driving a 25a bridged rectifier, with a couple of v large electroytics in series across the output. The two caps have voltage sharing resistors and a time delay relay + resistor for soft start. Have been able to drive a 10 hp motor for the first time using this setup from standard house mains, though the workshop lights dim a bit on full load.

One thing to note is that 500v dc is *seriously lethal* and needs utmost respect and care. Any such psu should be in an all enclosing box, with hrc fuses on the op and non standard connectors so that nothing else can be plugged in...

Chris




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Greenfield Designs Ltd
Electronic and Embedded System Design
Oxford, England
(44) 1865 750 681
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