Pm-940v whine

nighthawkFmobil

nighthawkFmobil

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I finally have my Pm-940v setup and ready to go. Everything has checked out so far after a thorough cleaning but im getting a hight pitched whine. It does it when i have the belt renoved from the motor pulley. It also seems to speed up with motor rpm as you can hear at the end. Wondering if anyone has any hints.

Thanks
 

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nighthawkFmobil said:
I finally have my Pm-940v setup and ready to go. Everything has checked out so far after a thorough cleaning but im getting a hight pitched whine. It does it when i have the belt renoved from the motor pulley. It also seems to speed up with motor rpm as you can hear at the end. Wondering if anyone has any hints.

Thanks
Click to expand...
It sounds like it's trying to do an impression of an old dialup modem. :p Does only do it when the belt is disconnected or also with the belt disconnected? I can check to see if mine does the same thing. Is the sound coming from the motor or VFD?
 
Bob D said:
It sounds like it's trying to do an impression of an old dialup modem. :p Does only do it when the belt is disconnected or also with the belt disconnected? I can check to see if mine does the same thing. Is the sound coming from the motor or VFD?
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It does it with the belt connected to motor and spindle, both hi and low setting. I was trying to watch another 940v owners YouTube videos but i couldnt make the sound out on his.
 
nighthawkFmobil said:
It does it with the belt connected to motor and spindle, both hi and low setting. I was trying to watch another 940v owners YouTube videos but i couldnt make the sound out on his.
Click to expand...
Mine does the same. It's more noticeable at 60hz or less, but that may just be because the overall noise increase at higher rpm's. I'm not sure why I never noticed it. Maybe my ex-wife was right when she said that I didn't listen.
 
Adjusting the carrier frequency to the top end of the vfd's scale (0-15khz) does eliminate the singing when i turn speed up past about 10hz. At that point my machine is very quiet. Just not sure how reliable the vfd or motor will be running a higher carrier frequency ill have to look into it. Id probably rather deal with the noise if excess heat when running at a higher carrier frequency is inevitable. Do people run these things at say 12-15khz? At what point is it risky?

Is this just a normal occurrence with these vfd/3phase motor setups? Its not unbearable but it definitely seems to stick out to me. Maybe some kind of filter will help.
 
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I would run it at 12 kHz, it will be fine in this application and size motor. I would not worry about it. The lower the Hz the more noticeable the whine will be, nothing can be don about that. Also as you decrease the Hz below the motor base speed, the Hp will drop off in a somewhat linear fashion. In the inverter/vector type motors with high to end RPM, I would not run it below 20 Hz. My mill motor is 20-200 Hz.
 
Increasing the Carrier Frequency above the base value (typically 4kHz) requires derating the VFD nameplate horsepower due to higher inverter heating. IGBT heating occurs almost entirely during the brief moment (couple of nanoseconds typically) when the voltage is switching ON or switching OFF. The more pulses per second, the more switching occurs and therefore more wasted heat into the inverter. The chart typically looks something like this:

1630595970698.png


This doesn't matter so much for us hobby guys, but it could if you run your machines at > 50% load continuously.

The whine is annoying and is especially important for elevator control and HVAC in office building where it is quiet and the chirping would annoy people. Pumps, fans, power generation, etc. will typically shoot for the lowest carrier frequency reasonable as it improves the electrical/mechanical conversion efficiency, especially in large motors.
 
The PM-940V uses the Delta VFD's, the ones I have worked with do not have an output current derating for their single phase input models. Derating is mostly an issue with bigger motors, long motor cables, continuous high duty cycle and motor type. Since the PM-904V comes with an inverter/vector TEBC motor it should not be an issue. Table is from the Delta manual, interestingly they say the factory default is 15 kHz on the 1-5 Hp models, I usually recommend 12 kHz on these smaller VFD's.

PWM Carrier Frequency Selections.jpg
 
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