Making a high amperage DC reversing circuit

[cjphelps]

I have to build a circuit that every 5 minutes reverses the polarity on an anode and cathode reactor. The catch is, it is 40volt 165amps DC that I am switching. Can anyone help me select the high amperage components to do this?

 

[VinceS]

http://www.mouser.com/ is a good source for component parts...

 

[gar]

080825-1857 EST

cjphelps:

What is the source of the 40 V? Is it a transformer rectifier, or something else? Is it a bridge rectifier or full wave rectifier from a center tapped secondary?

Some possibilities:

1. Switch the primary with a relay to remove power. After DC current is zero change the state of a double pole double throw relay to reverse the DC leads. Last restore primary power.

2. Change the rectifier to include two SCRs in place of two diodes. This provides an on-off switch that turns off at a current zero crossing, and thus no arcing. This provides one polarity. Create a second one with diodes and SCRs reversed for the other polarity.

Look at AB or Sq-D for high current relays. You really do not want to switch the DC side with current flowing if you want long contact life that is why I suggested removing power on the AC input side before switching polarity.

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[dbuckley]

I'd go for a pair of mechanically interlocked contactors, but you may have a problem with the DC ratings. Can you control the power source so the contactors dont have to make/break the load...?

Oh yeah, and a micro-PLC to drive the contactors. You can do it cheaper, by far, but you'll lose the money and more in labour to wire it up and make it work.