# Heat-sink on Curtis Controller



## Moltenmetal (Mar 20, 2014)

You need to mount it to a heatsink of some sort unless you want to limit peak currents considerably. I have mine mounted to a large aluminum plate with the heatsink below it, with a muffin fan mounted to the heatsink's lower surface. No problems with excessive temperature, despite the fact that the heatsink fins are pointed downward.


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## GoElectric (Nov 15, 2015)

Hi MM,

Thanks. I think it is such a silly design to have the fins on the bottom.

AND a fan, you say?


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## Moltenmetal (Mar 20, 2014)

Yes, a fan to counteract the bad orientation of the fins, otherwise I agree- the fins do little useful! But with just a muffin fan blowing air through the fins, their orientation is no longer any kind of problem- local air velocity next to the fins drives down the fin temperature to near ambient and makes them quite effective.

Remember that you'll come roaring off a highway exit to a dead stop on a hot day someday, then want to peel out from that stop- without relying solely on the heat capacity of the controller to handle the peaks in heat generation. The semiconductors in that controller are too spendy to risk cooking them.


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## Caps18 (Jun 8, 2008)

There are a lot of things they should have built in to this controller. Contactors, fuses, key relay, shunts... It would be nice if all I had to do is hook up the high voltage DC battery and the AC motor wires, along with all of the other control wires.

But, it isn't that bad that I wouldn't use it again. And I will be happy with it if my wiring all works.


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## GoElectric (Nov 15, 2015)

I love this website - good practical advice. 

I had to ask because it didn't make sense they would design a controller that way.

I guess if one did the math on 500 amps at 120V and 10-15% losses.....
That's almost 1000 watts, so - yeah, it will heat-up pret-ty fast.

While we are at it, one place I was thinking of putting the controller is behind the grill - I kind-of nixed that idea because it is a vulnerable spot, but I was wondering: just how important is it to keep the 3-phase wires short? I hear there is a fair bit of EMF?

Oh, that leads me to another question: how DOES that controller work anyways? Does it vary the amplitude of the AC output, or does it chop the waveforms?

Thanks.


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## Coulomb (Apr 22, 2009)

GoElectric said:


> Oh, that leads me to another question: how DOES that controller work anyways? Does it vary the amplitude of the AC output, or does it chop the waveforms?


It does chopping (Pulse Width Modulation) to generate three AC waveforms. It varies the amplitude and frequency of the output to cause the motor to drive or regenerate. There is some complex maths in there to calculate various vectors and so on.


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## GoElectric (Nov 15, 2015)

Hi. That explains the EMF then!


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## Moltenmetal (Mar 20, 2014)

Caps18: I'm very glad they didn't incorporate anything of the sort you're describing INTO the controller. Because the mechanical crap like the contactor is outside the controller, I can easily replace it when it fails- as others have had to do. Apparently HPEVS went through a batch of bad contactors... A very little easy wiring is a small price to pay for user-maintainability...from what I've seen, getting into the controller's case is no picnic, so you definitely don't want to have to disassemble it if you don't have to. The controller as designed is very high ingress protection (IP) rating, with just one big sealed connector and some terminal posts extending through the case. That can't help but improve its durability in an auto environment.

Same with the heat sink: by keeping the form of the controller as small as possible, you get options for mounting. Don't have room for a heatsink and a fan? Or live somewhere really hot? You can add a liquid chill plate instead. Want to mount it upside down? I presume you can do so- as long as you have a means to see the status LEDs.

You can estimate the average dissipation from the performance data given in the Curtis datasheet, and they don't lose anywhere near 10-15% of the input energy for sure. Thank goodness, because 500 A x 120 V is 60 kW, and 10% of that is 6 kW, not 1000 W...

At the risk of being a Curtis fanboy, I can say that I think HPEVS's implementation of that controller for vehicle applications is excellent, with only a minor glitch in my software version to complain about so far- one which is only a problem because I don't want to splash out on a programmer. Mine has only been driving for a year, but so far, so good!

I don't have EMI/RFI problems but my AC wires are short and run together in a bundle. But like all aspects of a design, there are a number of compromises to be made to suit your car. By mounting mine to a plate with the heatsink beneath, the fan can still get access to plenty of fresh air from beneath while the controller is kept high and dry. The plate's extra area more than makes up for the extra contact resistance between the controller and its heatsink. But of course all that will vary from car to car.


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## GoElectric (Nov 15, 2015)

Hi - good discussion. I don't have much to say about the shortcomings (or not) of the Curtis except I wish the fins were on top. Can someone post a pic of how they mounted it on top of an upside-down heat sink (with a fan)? 

I think mine will be going on top of the battery box, directly above the motor, so not a lot of air-flow up there. 

Jim


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## mizlplix (May 1, 2011)

LOL, Yes, heat sink. I had a 2" finned style with fan and still got an occasional heat shut down. But a good friend, (Ivan) made me a thin liquid cooled chill plate. Now, it never gets much above ambient.

I too am glad that many things are not part of the controller as I have replaced the contactor twice. Both times were my fault as I was using a pack voltage way above the recommended. (and the precharge interval is not adjustable to compensate.)

Yes, at all costs, keep the motor leads as short as humanly possible. Mine are 18" long. and yes, they are bundled together with no RF problems.

Run your encoder (resolver) leads as far as you can away from those motor leads. The encoder uses a very weak signal and any RF will screw everything.

Miz


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## Caps18 (Jun 8, 2008)

Maybe inside of the controller isn't the right term then, but as a separate box that can be hooked up easily right next to it with the right components. I think the DIY electric car world would expand if you could buy pre-wired components that you could just drop into a vehicle, plug in the battery, hook up the transmission, and connect the wires to the vehicle that need to be connected. Mounting motors and boxes would be the challenging part then.


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