about 1 KVA or more. I have one already but I want another so I can get 460 volts at 5 amps or more from 230v. Nobody uses these things any more because they have RCDs that don't weigh 20kg!
We need to test 600 volt air compressors. 460v will do once it's rectified.
farmerjohn,
Aug 13, 6:56am
I have one at the farm have not used for many years, will be back at farm on Friday, how can I contact you,? John
trade4us2,
Aug 13, 7:42am
Thanks, I did look and didn't see that one.
trade4us2,
Aug 13, 7:47am
I suppose you could put up an auction. It's for a non-profit organisation. I have made a bid on one.
bill1451,
Aug 13, 8:08am
How are you going to test compressors with 460 volts, 3 phase power runs at 120 degrees between phases.ie when 1 phase is at +peak phase 2 is at zero, and phase 3 is at -peak, cant see how you are going to achieve anything as you may have 460v but it will be just that, Everything will be in phase. 3 phase is a rotating magnetic field. Ah well only been in this game 46 years, rules of physics must have changed.
mm12345,
Aug 13, 8:22am
The OP wants about 600v DC - not AC. So 230v AC through a (230-115v) stepdown transformer, wired in reverse (secondary as primary), primary then outputs 460v AC. Bridge rectifier on output 460v RMS , will give ~650V DC peak with no load.
The transformer should be the easy bit, as step-down transformers are common, though (when using it reversed) as the primary (being used as secondary) will be rated for 230V - not 460V - some prayer needed that the insulation on the winding is up to task, and smoothing/regulating output to get near enough to the target 600V DC under load would need some thought.
trade4us2,
Aug 13, 8:27am
The compressor runs on DC so obviously a rectifier will be used. An electrical engineer and qualified electrician will be wiring it up. I'm just getting another transformer. I was designing and making thousands of transformers for NZ power stations and power companies and factories from over 50 years ago.
trade4us2,
Aug 13, 8:30am
It just occurred to me, why don't I just use a voltage doubler? We have some 100,000 volt diodes and capacitors.
mm12345,
Aug 13, 8:30am
So two "budget" options, Use two isolating transformers, rectify, then run the DC output in series, or use a 2:1 "step-down" transformer in reverse as a "step up", and rectify the single output.
trade4us2,
Aug 13, 9:10am
I would not want to use a step down transformer in reverse as the flux density of the core would be wrong. What's wrong with having two 230-230v transformers with the primaries in parallel and the secondaries in series?
kwaka5,
Aug 13, 9:28am
Could probably find you a dc drive if that's any help. Might be a bit big for what you are doing though. We still run a few DC motors at work and have some spare motors and drives from redundant plant.
trade4us2,
Aug 13, 9:37am
We have a very large Variac, and propose to wind the voltage up slowly in case there's a fault in the compressor. That should be much better and safer than applying 600 volts suddenly.
marte,
Aug 13, 11:46am
You guys have fun jobs.
bill1451,
Aug 14, 6:42am
Mmmm black and charred, hanging from equally black and charred batten holder, Paddy the Irish electrician, had not heard of "3 plating"
aredwood,
Aug 15, 8:30pm
Really curious as to why you have air compressors with 600VDC motors. And not simply normal AC motors. Are they normally part of some installation that has reticulated 600VDC?
You would probably want to earth the centre tap of your "secondary". But otherwise I don't see why having the outputs of 2 isolating transformers in series wouldn't work. Apart from if you connect them out of phase. But then you simply won't get any voltage out of them.
johotech,
Aug 15, 8:56pm
Electric train perhaps?
Earthing the center of the outputs would defeat the purpose of having "isolating" transformers and make the whole setup considerably more dangerous.
Yes, but this is for test purposes only, for a few minutes.
tintop,
Aug 16, 4:02am
Ah - It all comes clear! :)
aredwood,
Aug 16, 11:45pm
I said that from the point of view of if you instead earth 1 end of the series string. The insulation at the other end would then need to withstand double the normal voltage. But otherwise agree with you if the purpose of the isolating transformers was safety. Instead of being used to double the mains voltage.
trade4us2,
Aug 18, 1:08am
The secondaries and the compressor will not be earthed in any way. They will be on a test bench with nobody near them. If the compressor works it will be run for a few minutes at most.
Since the public registrations are closed, you must have an invite from a current member to be able to register and post in this thread.
Have an account? Login here.