DC speed control problem

[Swede]

Hi Guys, I picked up a used KBCC speed control, a nice, big unit which can handle 16 Amps DC output. While I was gloating, I noticed one of the components is shattered.

It is a 600V rectifier, silicon, 25A, TO-220 package.

Digikey does not have a direct replacement. My options are to go with either...

1) A 25A 400V device, or
2) A 20A 600V device

I'm leaning towards option 1 to get the full, rated current, but perhaps option 2 would be a better choice for longevity, with a possible current derate. Any thoughts? Anyone else have a KBCC speed controller from KB Electronics?

Swede

[JFettig]

Howabout 35a 600v?
http://www.allelectronics.com/cgi-bi...356&type=store
here are my fav online electronics stores:
allelectronics.com
jameco.com
mpja.com

Jon.jon

[Al_The_Man]

Swede, The voltage rating for a diode should be the PIV or peak inverse voltage which is the max reverse voltage that will be present, If the voltages in the unit are not even close to 400vdc then there should be no problem. Obviously the max current is when the diode is conducting at that point the voltage is almost zero (across the diode), when the diode is non conducting the current is zero but the voltage can be maximum (reversed biased). If you have a rectifier with no smoothing the reverse voltage will be 1.4 x AC.
With a smoothing capacitor after the rectifer then go 2x AC voltage rating.
Al

[ViperTX]

Swede, I suspect that is part of the bridge...so either option should be okay. Option 1 will make you feel better.

[Swede]

Thanks guys, I appreciate the responses. Hopefully, that's all that is wrong with this unit, I haven't even powered it up yet and won't until I replace the diode.

[lerman]

Originally Posted by Swede Thanks guys, I appreciate the responses. Hopefully, that's all that is wrong with this unit, I haven't even powered it up yet and won't until I replace the diode.

Swede,

Unless the rectifier is "shattered" because it was hit with a hammer, there is a good chance it exploded because of an overload. I would check the filter capacitors for short circuits before I fired it up.

Ken

[Swede]

Thanks Ken, I will also check the fuses and other obvious things that I can with my limited understanding of the system. The replacement parts are inbound, I'll post the results