Tractorsport Flowbench Forum Archive

Posted: **Mon Oct 12, 2009 11:54 am**

Look at the size! SCR, POT, and transformer.

Posted: **Tue Oct 13, 2009 10:30 pm**

Please don't mind me asking cspeier, is that just some gathered peices or a kit from somewhere? I am new to all this stuff and have just been reading the last week or so, trying to gather info to possibly build my own bench. Thanks Josh K.

Posted: **Tue Oct 13, 2009 11:02 pm**

I did a lot of research on this and had my mind set on the Payne brand, about $800 for everything. Then I found the same thing from Control Concepts for a total of about $590. Then I kept calling and found the same thing from HB Controls.

$175.00 LPC-90HDA controller
$50.00 HBC-POT-1 potentiometer
$45.00 PS-240 power supply
___
$270.00 total

I'm not sure why anyone would mess with anything else!

I'm close to having it up and running, so I'll keep everyone posted.

It's a bargain, you can order direct.

Posted: **Wed Oct 14, 2009 12:14 am**

Please help me out here but what Payne controller cost $800.00 and just why do yo need 80 amps? When two 120vac lighthouse motors won't even draw 20 amps.

Are you trying to speed control all 8 motors?

Rick

Posted: **Wed Oct 14, 2009 12:30 am**

Posted: **Tue Oct 20, 2009 6:37 am**

That heat sink looks to small to keep the scr cool at a constant 80A.

Looks more like a 30A heat sink to me.

Not trying to rain on your parade, just be aware these things let the smoke out when pushed.

Posted: **Tue Oct 20, 2009 3:38 pm**

Posted: **Tue Oct 20, 2009 8:09 pm**

Posted: **Wed Oct 21, 2009 2:21 am**

These modules will certainly handle a high inrush o/k, but if there is an eighty amp module available, it is certainly what I would be using.

Another point, is that these modules need to be de-rated for actual heat sink temperature rise.
The full rated current specification is with a hypothetical heat sink held constantly at 25C. That is not realistic, but it is how all power devices are rated.

So in practice, an 80 amp module might only be able to handle maybe 60 amps on a "fairly hot" heat sink, in the real world.

Posted: **Wed Oct 21, 2009 9:27 am**

OK, this LPC-90HDA is a 40amp continuous with a 90amp relay.

The one I have on the way is a 70amp comtinuous with a 125amp relay.

Should be covered, agree?

Posted: **Wed Oct 21, 2009 3:05 pm**

Posted: **Wed Oct 21, 2009 3:39 pm**

It's 3 x 4.5.

Here is a photo:

I'm getting close, need a few odds and ends.. See if i can make smoke!

Posted: **Wed Oct 21, 2009 4:05 pm**

Monitor the heat sink temperature, if it gets very hot as I expect it will, fit a fan to it. That particular type of heatsink is made to blow air through, not work by natural convection.
The natural convection types always have the fins on the outside.

Anything below 50C is fine, anything much over 60C is going to kill your power module eventually, if not straight away.

Posted: **Wed Oct 21, 2009 9:31 pm**

Posted: **Thu Oct 22, 2009 3:04 am**

The temperature of the heat sink will tell you if there is a problem or not.

Try it first and see.

I can take you step by step through the thermal calculations, and the rationale behind de-rating parts at elevated temperatures, it is all fairly basic power electronics engineering.

But the short simple answer is, if it is too hot for humans to comfortably hang onto with bare skin, the electronics will not be all that happy with the situation either........

Tractorsport Flowbench Forum Archive

My 80amp SCR Motor Controller