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I'm starting to build a piece of test equipment to test a trip device for switch gear breakers. I need to amplify an AC current source. When the breaker is in service the trip device receives its current sensing from the secondary of the ct on the breaker.

I want to be able to control the current via PWM as I plan on using a TI microcontroller for the brain of the system. I'm struggling with the AC amplification section. I am trying to find the LED drivers that have a external MOSFET and try it as I would have current sensing and could PWM control it. Then I could use the MOSFET I need as I need to be as close to 60 amps as I can be.

What do y'all think?

Thanks!
Jake

Robherc KV5ROB
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TXROCKS
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    I think it's very difficult to understand what you're trying to achieve. Do you have a schematic? When you say "amplify the current", where does the extra power come from? – Nick Johnson Jun 22 '15 at 14:56
  • Thanks Nick, I think current amplifier may have been a poor choice of words. It looks like my dropbox didnt sync so I cant get to my preliminary schematic at the moment. – TXROCKS Jun 22 '15 at 15:19
  • Thanks Nick, I think current amplifier may have been a poor choice of words. It looks like my dropbox didnt sync so I cant get to my preliminary schematic at the moment. This system will be powered from 120vac but can be rectified to DC, so I have that available as a power source. An adjustable AC constant current source would be a better term I think for this. I was thinking amplification as a method to adjust the current level. My other thought was an inverter circuit. It has been to long since I have had an electronics class. Thanks again, Ill get the flow chart and schematic up soon – TXROCKS Jun 22 '15 at 15:29
  • So, you want to generate a current-regulated AC waveform, and you have AC mains power to work with, is that correct? – Nick Johnson Jun 22 '15 at 15:47
  • Yes, and yes. Looking a bit further into this I can use the TI MSP432 and use one of the current outputs (20mA max) to drive a op amp which can drive the high I MOSFET. Thanks again for putting up with me! – TXROCKS Jun 22 '15 at 15:56
  • I don't think you're going to be able to do this with a MOSFET, because MOSFETs have body diodes, so you can't use them for switching AC. I'll leave it to someone with more knowledge of AC power to provide a better solution. – Nick Johnson Jun 22 '15 at 16:00
  • Are you looking to build something like this? http://us.megger.com/circuit-breaker-test-set-cb-1/ – Tyler Feb 25 '16 at 00:10

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