MeanMachine1980
Aluminum
- Joined
- Dec 30, 2017
Has anyone used a "sine wave filter" with a VFD to quiet up the motor whine caused by the switching freq from the VFD?
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After that the filter is whining :p
Has anyone used a "sine wave filter" with a VFD to quiet up the motor whine caused by the switching freq from the VFD?
The sine wave filter will not affect the whining noise in the motor. the only time you need to use those is if you have a VERY old motor that can't be easily replaced or has compromised insulation already, or the distance from drive to motor is over 2000ft. Otherwise, it's a waste of money.
The only thing that will change the pitch of the whine in the motor is to increase the carrier frequency, the basic rate at which the transistors are fired. The higher the CF, the higher the pitch of the whine sound and once you go above 10kHz, humans can no longer hear it. But that then increases the switching losses in the transistors, so it DECREASES the capacity of the VFD, requiring de-rating.
Side Note: If you have used a VFD to convert from single phase to 3 phase and in doing so, have doubled the size of the VFD, then you need not worry about further de-rating the VFD for the higher carrier frequency. Doubling the size of the VFD is to take care of getting larger diodes and more capacitors on the rectifier end only, so you actually end up with larger transistors than you needed. Carrier frequency affects the inverter end only, so having those larger transistors means the added losses are dealt with. So if you are using the VFD as a phase converter, you can crank up the CF until only your dog knows you are running the machine.
Side note of the side note: If you have bought a VFD that is ALREADY rated for single phase input, then this would not apply. What's different about those drives is that the rectifier components are ALREADY larger than necessary, so they DON'T increase the transistor sizes, meaning you WOULD need to de-rate the drive if increasing the CF.
Thanks everyone for all the insight. I have a southbend 13" lathe with a 2hp drawing 5.8 amps 220 three phase motor. Im currently looking for a VFD to drive the lathe and want it to be as quiet as possible. For some reason I cant stand that squealing motor noise that is created from the PWM. I also dont want to ruin the motor of VFD by simply increasing the carrier freq. It seems every video on the internet of a VFD driven machine has this whine....
Thanks again everyone
SB have made plenty of chips off the back of vee and flat belts with a decent selection of ratios.
Variable speed DC motors do not get an entirely free pass, either. What is AFFORDABLE to power them - SCR class much above 2 HP, SCR OR PWM 2 HP and down, operate using each "half" of a line-frequency sine wave, switched. 120 Hz, US grid, single phase source. Treble that for 3-P-only DC Drives.
All that is well within the range of human hearing, even with a good "ripple filter". It is, at least, in a far less unpleasant portion of the audio band, so I doos it.
Next step - published how-to, thanks to Yaskawa/Magnetek, is to add capacitor filtering, for the goal of "Quiet Elevator". That approaches variable voltage off a DC battery pile quiet.
Sure makes most lathes sound like rattle-traps in the silence, though, so.. how far should we chase ANY of it before just wearing silencer headsets or ear-buds?
You planning 16-hour back-to-back shifts in front of that lathe? Or something else?
Variable speed DC motors do not get an entirely free pass, either. What is AFFORDABLE to power them - SCR class much above 2 HP, SCR OR PWM 2 HP and down, operate using each "half" of a line-frequency sine wave, switched. 120 Hz, US grid, single phase source.
my scr drive and baldor 3/4hp motor made my southbend nine into a 120hz tuning fork. you could feel and hear it everywhere. i added an inductor and you can't even hear the motor.
The sine wave filter will not affect the whining noise in the motor. the only time you need to use those is if you have a VERY old motor that can't be easily replaced or has compromised insulation already, or the distance from drive to motor is over 2000ft. Otherwise, it's a waste of money.
The only thing that will change the pitch of the whine in the motor is to increase the carrier frequency, the basic rate at which the transistors are fired. The higher the CF, the higher the pitch of the whine sound and once you go above 10kHz, humans can no longer hear it. But that then increases the switching losses in the transistors, so it DECREASES the capacity of the VFD, requiring de-rating.
Side Note: If you have used a VFD to convert from single phase to 3 phase and in doing so, have doubled the size of the VFD, then you need not worry about further de-rating the VFD for the higher carrier frequency. Doubling the size of the VFD is to take care of getting larger diodes and more capacitors on the rectifier end only, so you actually end up with larger transistors than you needed. Carrier frequency affects the inverter end only, so having those larger transistors means the added losses are dealt with. So if you are using the VFD as a phase converter, you can crank up the CF until only your dog knows you are running the machine.
Side note of the side note: If you have bought a VFD that is ALREADY rated for single phase input, then this would not apply. What's different about those drives is that the rectifier components are ALREADY larger than necessary, so they DON'T increase the transistor sizes, meaning you WOULD need to de-rate the drive if increasing the CF.
Hello Jraef
Here is a post that I found from a few years back. You were helping out a gentleman with a similar issue I think?
http://www.practicalmachinist.com/v...put-side-380v-non-inverter-duty-motor-292404/
So I may be looking at a load reactor connected between the VFD and the motor?
The distance between the VFD and motor would be within 5ft. My 220v single phase source will be coming from about 40ft away. I plan on installing the VFD in a small cabinet attached to the back side of the lathe near the motor base.
So a load reactor in front of the VFD would help protect the VFD then?
Thanks
Watch out on the over-rating. Larger switching devices also tend to be slower, and bigger VFDs may have lower maximum switching frequencies. It is true that they will have better cooling, and so will tend to be less strained.
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