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Large Variable Dc supply

I am trying to put together a variable 220V DC supply running from 3 Phase AC. This needs to be able to supply around 100Amps to a very inductive load (~15H (!)). I have decided to use a 3 phase step down transformer and then use a 3phase bridge SCR to get my variable DC (will use burst firing rather than phase angle control in order to limit EMI).

Do you think it would be possible to just connect this straight up to my load?... Im guessing I do not require any smoothing due to the size of my indutance.

Are there any other factors I should consider? Ideally I want to be able to vary the power to the load quickly.

Also.. how would I go about turing this off quickly?

Thanks for your help.. any ideas and things I should think about would be greatly appreciated

Ben

Reply to
BAHarrison
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15 H sorry not an abbreviation that is familiar to me.

What is wrong with a welder?

Reply to
SQLit

With a highly inductive load, EMI is greatly reduced because di/dt will be limited even with sudden switching.

There are other factors to consider, but at least

  1. Provide for energy absorption in case your load suddenly opens.

  1. Provide other protection, such as a free-wheeling diode in case you power supply suddenly opens.

If you don't know what you are doing, hire a qualified Registered Engineer to bless your design.

Bill

Reply to
<salmonegg

It's late- so please excuse the maths if they are wrong..

The OP seems to want to interrupt the circuit quickly- say in 1/100 seconds.. The energy absorption system would have to handle some 7.5MW for that duration..

I am starting to wonder what it the OP wants it for..

It sounds like a pulse cannon or an EMP generator to me.. ;)

Reply to
Palindr☻me

Henry I imagine.

Reply to
operator jay

" snipped-for-privacy@gmail.com"

if its a step down like he said the SCRs should go on the primary not the secondary as the currents will be lower. wired in a triac configuration.

to turn it off quickly i would use a switch or relay.

sounds like an arc gap transmitter to me.

Reply to
TimPerry

Nothing as exciting as that i can ensure you!

Its for a large 65" electromagnet for lifting steel plate. We want to be able to add a variable lift strength so that we can select the number of plates to be lifted. As it is used for lifting steel beams as well as plate, the operator needs to be able to switch on and off full load (lift and drop) as quick as possible.

Currently we use a 220Vdc supply and mechanicaly interlocked contactors to switch the magnet on and off... switch off is achieved by connecting a dump resistor across the magnet and reversing the voltage over it.

Reply to
BAHarrison

i would think that the liability involved should things go awry would preclude any "home brew" solution.

i don't know much about magnetic cranes... i had always supposed they were AC magnets.

Reply to
TimPerry

Bill Kaszeta Photovoltaic Resources Int'l Tempe Arizona USA snipped-for-privacy@pvri-removethis.biz

Reply to
Bill Kaszeta / Photovoltaic Resources

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