simple power supply & dc isolation

[rmayer]

I have a dirty dc supply consisting of rectified variacs on a common stepper-motor shaft. Currently I have 1kVA isolation transformers in line that have 10amp breakers built in. I'd rather switch out breakers and try to pull closer to the wall rated 15A or if it is available 20A. I have circuit overload provisions for these higher rates so rest assured I'm not just trying to get around a popping breaker. Questions are how do I best provide dc isolation from the ac? The variac doesn't isolate at all does it?

Adequate torroidals seem o be hard to find or expensive. I thought I was maxing out what Mouser and digikey had to offer at 1kVA costing around $300 each (X 3, one for each phase). Anyhow I'm trying to set up ugly constant voltage (10V +/-5, up to 150 amps) dc power, SMPS is a bit advanced for me any suggestions?

Thank you in advance.

 

[itsmoked]

Whoa whoa.. 10V +/-5 (Volts) ?!!?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[rmayer]

So, the load will vary amongst a few different applications and the PSU needs to be able to support each one. Its an electrochemical thing with varying electrolyte and therefore varying conductivity and ion targeting. thats why the +/-5V

 

[itsmoked]

Ok. You are correct, no isolation with Variacs or any autotransformers.

You need 1-to-1 power isolation transformers. Digikey would NOT be the place to get these.

Were it me, I'd go to your local electrical supply house. Most every town has at least one and ask about getting some.

For much less weight you would go for a SMPS. They will do the rectification at higher frequencies with much smaller transformer requirements.

I'd check Ebay. I have bought many larger than 1kW rack mount SMPS that have both knob controlled current and voltage control on the unit. You may find one that runs about the same price as three transformers but provides much more, like, including the isolation.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScottyUK]

If you have a three phase supply available there are a few monster power supplies from HP's 62** series at knockdown prices. I picked up an 8V 580A one for about £900 to use when making very low resistance measurements. All the refinements you would expect of a top class PSU.



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