# Gigavac GV200QA humming, buzzing noise



## asymptonic (Oct 14, 2021)

Presumably the difference is in the PWM. In the Q models it's provided externally by the inverter. In the M models it's done in the contactor. I'm guessing Gigavac tuned the PWM in the M model for efficiency. Maybe worth emailing Gigavac to ask for more ideal settings?


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## asymptonic (Oct 14, 2021)

The spec sheet references this application note which may help.


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## balex97 (Nov 25, 2021)

Thanks for the application note, will give it a try.
Also try to contact Gigavac in Germany and US (they have closed due to Thanksgiving so have to wait till next week)


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## cricketo (Oct 4, 2018)

You could try adding a capacitor for filtering that noise out. Just mind the polarity if it's an electrolytic one.


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## remy_martian (Feb 4, 2019)

Just like a music box mechanism, if you have the contactor sitting on a large piece of metal, it could act as a mechanical amplifier. You may want to revise how you have your contactor mounted as another approach.

Another method is to crank the PWM up to 14kHz...that way it only drives kids nuts with the sound 😂


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## balex97 (Nov 25, 2021)

remy_martian said:


> Just like a music box mechanism, if you have the contactor sitting on a large piece of metal, it could act as a mechanical amplifier. You may want to revise how you have your contactor mounted as another approach.
> 
> Another method is to crank the PWM up to 14kHz...that way it only drives kids nuts with the sound 😂


Also considered that.
But that's not the case, since I mounted this one on a wood plate and I also tested it on a aluminum plate before - same noise.
So it definetely comes from the contactor itself. It's mounted properly, the bolts are tight so no vibrations or other things from that.

Tried to rise the PWM but it stops at 1000Hz. So no chance to blow the kids ears


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## remy_martian (Feb 4, 2019)

Mounting it tight couples it to the mounting plate. Does it make the same level of sound while dangling in the air? 

Are you mounting it dead center on the plate?


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## balex97 (Nov 25, 2021)

So today I called the German support and he refered me to the application notes. He didn't remember any case of humming contactors either and said it shouldn't be normal.
So I'm waiting for the US support to answer.



remy_martian said:


> Mounting it tight couples it to the mounting plate. Does it make the same level of sound while dangling in the air?
> 
> Are you mounting it dead center on the plate?


Tried it today. So I dismounted it and tested - the noise gets quieter. So the wooden plate definately amplifies the noise but it's still there.
I made a short video to demonstrate: contactor video


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## cricketo (Oct 4, 2018)

Seriously, try adding a capacitor. Connect it in parallel with the coil - it will absorb the pulses. Just make sure it's rated for the same (or above) voltage as the coil, and mind the polarity.


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## remy_martian (Feb 4, 2019)

Yup...that's giant mosquito annoying 😂


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## balex97 (Nov 25, 2021)

So I got an answer from the US support today.
He said that the GV200QA is normally driven with 25kHz so people can't hear it.
With 430Hz is way too low and the sound is the contactor opening and closing at this speed. 
But the maximum frequency I can put in my settings is 1kHz. 
I don't know why and I also can't understand why nobody else has this problem because it's an extremly spreaded kit for electric car conversions.


cricketo said:


> Seriously, try adding a capacitor. Connect it in parallel with the coil - it will absorb the pulses. Just make sure it's rated for the same (or above) voltage as the coil, and mind the polarity.


Actually don't want to test this till I really know there's no other option to tweak this software.
But as I see there won't be another chance...


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## asymptonic (Oct 14, 2021)

Yeah, I plan to spring for the dual coil version in my build and either ignore the supplied one or use it for some other infrequent purpose.


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## remy_martian (Feb 4, 2019)

I think I see what's happening.

You seem to be changing the frequency instead of the duty cycle.

You need to fire the contactor at 100% duty cycle, then back the duty cycle off a few dozen percent after a hundred or two milliseconds. The contactor SHOULD NOT be opening and closing. If it is, your duty cycle is too low in the power save portion of the cycle.


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## cricketo (Oct 4, 2018)

remy_martian said:


> I think I see what's happening.
> 
> You seem to be changing the frequency instead of the duty cycle.
> 
> You need to fire the contactor at 100% duty cycle, then back the duty cycle off a few dozen percent after a hundred or two milliseconds. The contactor SHOULD NOT be opening and closing. If it is, your duty cycle is too low in the power save portion of the cycle.


I don't think that's correct. I was going through a bunch of that stuff with a Curtis 1236 controller recently. Contactor is driven via one of the PWM outputs, where duty cycle is used to adjust the output voltage to the coil. So like my battery nominal is about 50V, contactor has a 24V coil, so duty cycle is set for 50% for basically putting half the battery voltage to the coil. Then there is the second parameter for adjusting hold voltage in a similar fashion. THEN, on top of that, all PWM outputs on Curtis have an output frequency adjustment within a certain range. Changing that parameter has no effect on the duty cycle itself, just really how that duty cycle is achieved. 

Looks like the OP made up his mind though, so I will refrain from further input


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## balex97 (Nov 25, 2021)

cricketo said:


> Looks like the OP made up his mind though, so I will refrain from further input


So to get you right, I should take a 60V capacitor for the 48V coil. Which capacity would you suggest?
Here is my schematic, I circeled the trouble maker and inserted the capacitor as I would try it tomorrow:


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## balex97 (Nov 25, 2021)

Thanks to the power of editing this embarrasing post has been cancelled


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## cricketo (Oct 4, 2018)

Right, needs to be between 26 and 25. 60V is good. I would try something like 1000uF. Basically needs to be big enough to maintain voltage between the pulses, but not so big that it delays your contactor significantly from opening when voltage is removed.


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## remy_martian (Feb 4, 2019)

cricketo said:


> I don't think that's correct. I was going through a bunch of that stuff with a Curtis 1236 controller recently. Contactor is driven via one of the PWM outputs, where duty cycle is used to adjust the output voltage to the coil. So like my battery nominal is about 50V, contactor has a 24V coil, so duty cycle is set for 50% for basically putting half the battery voltage to the coil. Then there is the second parameter for adjusting hold voltage in a similar fashion. THEN, on top of that, all PWM outputs on Curtis have an output frequency adjustment within a certain range. Changing that parameter has no effect on the duty cycle itself, just really how that duty cycle is achieved


Thanks for making my point....
😘

The "hold voltage parameter" is not correctly set


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## balex97 (Nov 25, 2021)

These are the settings I put in the user program 
This is the demo mode, so it doesn't show the voltage.
The pull in voltage is 48V and the holding voltage is 11V. That's in the application notes from GV200


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## cricketo (Oct 4, 2018)

remy_martian said:


> Thanks for making my point....
> 😘
> 
> The "hold voltage parameter" is not correctly set


Okay, I think I caught up with your idea now. Lower duty cycle forms a secondary frequency, like 25Hz for 25%, which may be audible. That is plausible, but if one wants to utilize the economizer, capacitor is still the way to fix it. I think the reason PWM outputs in these things aren't smoothened by caps is because caps need to be picked for each load, which isn't known ahead of time.

Hold on, I wrote nonsense about 25Hz... need to think for a moment 

Okay, so I think this last idea is swill wrong, and my first thought was correct.

Let's say we want to have 12v holding voltage from a 48v (nominal) pack. That's the 25% the voltage, and we achieve it by using 25% duty cycle of the output. Now we have a 400Hz PWM driver, which means out of 400 possible pulses, it needs to put out every 4th pulse in order to maintain 25% duty cycle. If we write it like a binary number, it would look like this :

1 0 0 0 1 0 0 0 1 0 0 0 0 <--- 400 times every second. I don't think that sub millisecond gap would affect audibility of the signal.


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## remy_martian (Feb 4, 2019)

No.

He disclosed that the contactor is actually opening and closing when actuated....


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## balex97 (Nov 25, 2021)

remy_martian said:


> No.
> 
> He disclosed that the contactor is actually opening and closing when actuated....


Maybe expressed that a bit sloppy.
The contactor is closed after I fire up the vehicle. I can drive without any problems beside the noise.
The Gigavac vendor told me the following:

_What frequency is the GV200QA contactor coil being driven with? Gigavac uses 25kHz so that it can’t be heard (by humans). 
-Brian_

I told him that I run it with 430Hz and I'm not able to go above 1kHz due it's limited by the programm
Then he wrote the following:

_430 Hz is too low. The sound you hear is likely the contactor opening and closing rapidly. 
You could use a GV200FA and the same output by setting the PWM duty cycle to 100% (48vdc). 
-Brian_


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## balex97 (Nov 25, 2021)

I also went through the Hyper9 thread from OR-Carl where 4Foxtrot wrote the following: 

_6. Beg Hunter for the *OEM /dealer version* of the SME Tau software .. *Warning:* you CAN kill yourself/system ... but at the very least it allows you to lower the frequency of the contactor to make it almost silent !!! (and adds many more useful options). I cant post the software, but HERE are the help files which show capabilities._

So I guess he lives with that noise.
Tomorrow (today better said) I will go through all these things and be right back when I got any news.


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## cricketo (Oct 4, 2018)

balex97 said:


> _The sound you hear is likely the contactor opening and closing rapidly. _


It's really just micro-vibrating. Kind of like connecting a small DC motor to a source of audio signal - it will play it like a speaker.


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## asymptonic (Oct 14, 2021)

cricketo said:


> It's really just micro-vibrating. Kind of like connecting a small DC motor to a source of audio signal - it will play it like a speaker.


Then you may be hearing vibration of the coil. But yeah, Gigavac is expecting you to be able to set the PWM frequency outside of human hearing range (hence 25khz). It looks like you can't do that in the SME software.


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## cricketo (Oct 4, 2018)

Probably not the coil, but the contacts are oscillating under varying pull of the electromagnet.


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## remy_martian (Feb 4, 2019)

They better not be. That's my point, and what Gigavac said. That they are opening and closing. Reread what they wrote:

_"430 Hz is too low. The sound you hear is likely the contactor opening and closing rapidly"_

It would be an interesting, albeit shortlived, way to control motor speed


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## cricketo (Oct 4, 2018)

Gigavac just wasn't being pedantic with their response, possibly deliberately simplifying it for the average Joe.


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## remy_martian (Feb 4, 2019)

"Coil vibration like a loudspeaker" is simplifying it for the average joe. 

But that is not what they said, is it? 

And nobody is going off and changing the f*cking duty cycle to 80% on the holdin to see if the sound goes away, are they? Take 2 minutes of effort to check that. 2 many minutes.


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## balex97 (Nov 25, 2021)

So today I reprogrammed all parameters to check if they are set 100% right. 
Then put in the capacitor but this doesn't work. The inverter falls into Error mode and says "contactor open/short".
Tested it with a 60V 100µF capacitor, it was the only one with that specs to fit in my selection.
So the only way will be to turn down the frequency to 120Hz and try to mount it in a isolating way.


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## remy_martian (Feb 4, 2019)

What values did you set each of the parameters to?


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## balex97 (Nov 25, 2021)

balex97 said:


> These are the settings I put in the user program
> This is the demo mode, so it doesn't show the voltage.
> The pull in voltage is 48V and the holding voltage is 11V. That's in the application notes from GV200
> View attachment 125258


pull in time is 110ms now but all other parameters are as on the picture


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## asymptonic (Oct 14, 2021)

I'm curious since you have the software in hand. Can PWM be disabled in the interface or is the SME software hard coded to do that? Trying to see if a contactor with built in economizer or dual coil is even possible.


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## balex97 (Nov 25, 2021)

It can't be disabled (at least not for me although it's the OEM version) since the inverter needs to output the signal for the contactor. If there is any fault, it jumps into failmode in order no HV is passing through. So I think it's kind of a safety feature (bug ).


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## balex97 (Nov 25, 2021)

It can't be disabled (at least not for me although it's the OEM version) since the inverter needs to output the signal for the contactor. If there is any fault, it jumps into failmode in order no HV is passing through. So I think it's kind of a safety feature (bug ).


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## asymptonic (Oct 14, 2021)

balex97 said:


> It can't be disabled (at least not for me although it's the OEM version) since the inverter needs to output the signal for the contactor. If there is any fault, it jumps into failmode in order no HV is passing through. So I think it's kind of a safety feature (bug ).


I just meant can the *PWM* be disabled, not contactor control. Like set to 0hz or something. Otherwise I'd want to think about some PWM detecting relay to convert to a solid voltage to avoid PWM.


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## balex97 (Nov 25, 2021)

The values must be between 125 and 1000 Hz. If I type in others than that it automatically jumps back to this values. So PWM itself cannot be disabled.


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## asymptonic (Oct 14, 2021)

Dang.


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## balex97 (Nov 25, 2021)

At least I know why this thing is buzzing now and can fix that with some isolating material or something.


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## cricketo (Oct 4, 2018)

balex97 said:


> So today I reprogrammed all parameters to check if they are set 100% right.
> Then put in the capacitor but this doesn't work. The inverter falls into Error mode and says "contactor open/short".
> Tested it with a 60V 100µF capacitor, it was the only one with that specs to fit in my selection.
> So the only way will be to turn down the frequency to 120Hz and try to mount it in a isolating way.


That can happen due to additional capacitance delaying the contactor closing. Controllers usually have a programmable value as to how long they'll wait for contactor to close, you could try to bump up that value.


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## brian_ (Feb 7, 2017)

cricketo said:


> Lower duty cycle forms a secondary frequency...


Any square-pulse signal, including PWM at any non-trivial duty cycle (i.e. other than 0% or 100%), produces a horrible range of frequencies; the duty cycle will change that spectrum, but it will never just be the PWM pulse frequency. If the duty cycle is unchanging (as the contactor drive is while the holding level is applied), the extra frequencies should only be harmonics (multiples of the pulse frequency), not lower... but multiples of anything between 125 Hz and 1 kHz are annoying; it is almost as if the controller designer chose this range for maximum irritation.



cricketo said:


> Let's say we want to have 12v holding voltage from a 48v (nominal) pack. That's the 25% the voltage, and we achieve it by using 25% duty cycle of the output. Now we have a 400Hz PWM driver, which means out of 400 possible pulses, it needs to put out every 4th pulse in order to maintain 25% duty cycle. If we write it like a binary number, it would look like this :
> 
> 1 0 0 0 1 0 0 0 1 0 0 0 0 <--- 400 times every second. I don't think that sub millisecond gap would affect audibility of the signal.


That would be something like "pulse count modulation", not pulse-width modulation (*PWM*). PWM at 25% and 400 Hz means 400 pulses per second (so 25 ms per pulse cycle), with each pulse being 25% of the pulse cycle duration (so 6.25 ms on, 18.75 ms off). Changing the output of a PWM signal changes the duty cycle, not the frequency of pulses or the number of pulses. A constant PWM output (for a constant holding voltage in this case) means a continuing series of identical pulses, not a pattern of pulses with the number missing related to the desired output value because it's not binary coded, which the point of pulse width modulation as distinct from pulse code modulation.









The example binary string above could be considered 100 Hz PWM @25% duty cycle with only five possible output levels (0%, 25%, 50%, 75%, 100%)... but that's exceptionally crude.


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## remy_martian (Feb 4, 2019)

Turn the hold voltage up from 11% to 48%

11% is too low and the contactor is dropping out. It's PERCENT not VOLTS.

edit: even if it's volts, turn it up past 11....to 48V you can fine tune this later.


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