Dump load resistor noise

[Sparky01]

Good day all. I am using a Xantrex (trace) C-60 PWM charge controller and I get an aweful load buzzing noise from my dump resistor. I have used this for about 1 1/2 yeaqrs myself without a probem scince my power room is at my wind turbine. But a buddy of mine has his in a shed attached to the house. And the noise is very annoying. So do all PWM controlers make the resister coil make this sound or is it the type of resister that I am using?   http://www.ohmite.com/catalog/pdf/powrrib_series.pdf

Thanks

[Flux]

Some resistors are likely to be worse than others but it is something that you may have to accept. There are strong pulses of current in the resistor with high associated magnetic fields and there may additionally be thermal expansion noise.

Non inductive resistors will be quieter but most power resistors are wound as a simple coil for ease of manufacture.

Fixing the mounting to a resilient mount may reduce transmission to the walls. Direct radiated noise could be reduced by acoustic damping materials but you must not upset the air flow.

Your resistors look as though they are far from non inductive and if they have a steel mounting bar up the centre that will make things worse.

Flux

[Sparky01]

So there must be quite a few here that deal with a similar noise. I was wondering if I had something that I had done wrong. I notice about 6 months ago that DanB had an identicle resister to mine. I will try a couple of those suggestions to quite it down. I do like these resisters as they are very heavy duty.  Thanks for the comment.

[DanB]

Yes - I've always found the resistors to be noisy when powered by the PWM controllers...  best to keep them in the battery room or something, they can be annoying in the house!

My controller is much more primitive with 3 'heaters' that turn on/off as needed - so it's nice/quiet but not nearly so kind to the batteries.

[DanG]

I am very curious to the array you chose - load, resistor values and configuration?

The edge wound windings fitting loosely on the ceramic core are made to heave and shift with temperature changes so they chime nicely with vibrations. I think the C-60 operates around 200Hz so it must get some real rattle going.

You don't mention the operating temperature... but resonance set up by the C-60's frequency and duty-cycle width can be snubbed by inserting a damper at various places - a wood stove door gasket rope razor bladed into short chunks and inserted between coil windings, high-temperature mica sheet trimmed into a shim and made to act as hold off between a particularly noisy resistor turn and its ceramic, automotive exhaust or wood stove cement or HT auto exhaust silicone between choice windings and ceramic... the new kitchen flexible silicone cookie sheet material (500f) as core liner if you can get the center core out... the possibilities and combinations are endless..

Once the mechanical side is addressed - to get it more silent add a capacitor(s) across the C-60 output to reduce the square wave output waveform into less percussive event...

[jmk]

 I use the C-40 with my resistor and get the buzz noise too. Mine is in the garage so it's not annoying. It gets louder with more current being dumped. I like it because it tells me when I am dumping power. My computer is right on the other side so on a windy day I can tell if the battery is full. I wondered about it too, and am glad I read your post. I always thought that they did something with the frequency to make it buzz so you would know it's getting hot. Mine is mounted just like Flux described but I am going to leave it.

[Ungrounded Lightning Rod]

Once the mechanical side is addressed - to get it more silent add a capacitor(s) across the C-60 output to reduce the square wave output waveform into less percussive event...

NO CAPACITOR!  You'll pop the switching regulator.

It's the kind intended for regulating a resistive load, so it doesn't have an inductor in series with the switch.  (If it did you wouldn't have singing resistors.)  Put a capacitor across the output and you'll have a switch closing to connect two capacitors of unequal charge.  With ideal components that's the recipe for a spike of infinite current - and will real components the current does it's best to approximate it.  The switching transistor will be VERY unhappy with you.  B-(

[DanG]

Rats... I even asked one of my know-it-all buddies before I added that last bit on the capacitor and was told he didn't see a problem...  Now If I could just find the comment 'edit' button...