sine wave filters for VFD driven lathe

Has anyone used a "sine wave filter" with a VFD to quiet up the motor whine caused by the switching freq from the VFD?

After that the filter is whining :p

MattiJ said:

After that the filter is whining :p

Click to expand...

I haven't tried that. It probably does.

What if both VFD and filter can be placed at a distance from the machine and operator and the motor itself no longer whines?

Have you tried changing the switching frequency? It will lose some efficiency if you set the frequency higher (I think?) but it can make the noise less noticeable.

MeanMachine1980 said:

Has anyone used a "sine wave filter" with a VFD to quiet up the motor whine caused by the switching freq from the VFD?

Click to expand...

Check the VFD for noise, some are quite noisy.

Bill

They may not help a lot. A TRUE sine wave filter might, but most filters are for higher frequencies, and have little effect on audible tones.

Change frequency if possible, and if the VFD is not getting hot as it is.

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.

Jraef said:

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.

Click to expand...

What you are talking sounds more like du/dt filter.
Sine wave filters at least around this corner of world always imply big hunk of iron, massive capacitors and plenty of filtering at the carrier frequency.
(and should thus quiet the motor whining but the sine wave filter chokes can whine too..)

https://www.schaffner.com/fileadmin...r_solutions_for_motor_drives_applications.pdf
https://library.e.abb.com/public/a3be693a9ac8bf7bc125744e00339abe/ACS800_Sine_Filters_revG.pdf


"In order to eliminate or reduce unwanted acoustic noise levels, a sine-wave filter can be used. This will filter the pulse shaped voltage from the frequen- cy converter and provide a smooth sinusoidal phase-to-phase voltage at the motor terminals."

Yes.

I use a sine wave filter on the output of the inverter that feeds my entire workshop. The knee frequency of the filter is lower than the switching frequency of the inverter. The motors make no more noise than they would on utility three phase. The inverter and sine wave filter are almost inaudiable after I built them into a fan ventilated 1" MDF cupboard. Before that, the switching first stage of the inverters input power supply made most of the noise from the electronics.

No will, won't, etc. It does, that's what it's sold for!

Yes.

A TRUE sine wave filter is designed to attenuate all the harmonics of 50 or 60 Hz. That WILL work.

Most of the filters sold are as Mattij says, just a basic EMI filter, and will not do anything down in the audible range.

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

MeanMachine1980 said:

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

Click to expand...

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?

thermite said:

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?

Click to expand...

No, I just dont want to heat that nasty whine every time I turn it off and on or slow it down. I also dont want to stress the motor or VFD.

any 5% line/load reactor can be used with delta connected capacitors to deliver a sine wave to the motor, doing this will NOT remove the common mode voltage delivered to the motor. so you will have a slight reduction in the current flowing through the bearings, but not substantial.

As i discovered with my 1990's era vfds, you cannot use wye connected capacitors connected to ground due to some weird stuff and inconsistent behavior. it may work on other vfds that have a symmetrical 3 phase output at all times, but you can't use a 3 leg reactor, you need a 5 or 4 leg reactor and these cannot be found on ebay. i made my own by cutting up part of a 400hz transformer core and adding it to my 3 leg 5% line load reactor.


anyhow any 5% line load reactor that is sized correctly for the vfd can be used with delta connected capacitors at the motor, and this will remove the "whine" from the motor. but you will probably hear it from the reactor, probably won't be nearly as loud, and you can put it in a box with sound dampening material if you need to. again, phase to phase voltages will be a sine wave, but phase to ground you will see the pwm frequency (for a 240vac vfd, +/- 170vdc square wave)


if you have a 3% reactor, you probably need to keep the pwm frequency above 4KHZ, and if you have a line reactor that is not rated for line/load, then it probably has thicker laminations that were intended for 60hz only and using it to filter the pwm from the vfd *may* cause overheating particularly if it is heavily loaded.

thermite said:

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.

Click to expand...

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.

johansen said:

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.

Click to expand...

Almost physically painful to see Reliance-of-today name coupled with Baldor-of-today and under Asea, Brown-Boveri... ABB of today ...ownership.

I am old enough to remember when Reliance was far better at what they did than Rolls-Royce was at what they did, and Baldor was reasonably decent value for money at the cheap end of the motor market.

Would rather have a bad rash than any of their products less than 20 years old now.

Type T Reliance Electric and ENGINEERING shunt wound DC motors - large frame for the 10EE to octo-boxy RPM III, are only noisy off SCR drives during significant accel.

Ripple fliter, 20 mH @ 20A Hammond fixed inductance or my Lenze swinging choke sort that at once, growl a bit at the choke, but not as loud.

I have lesser-amperage Lenze for the 2 HP RPM III's.

Tad heavy those would be for an SB's frame. 180 VDC wound. Floor mount recommended if ever you try that route vs the Bald Dorito.

Jraef said:

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.

Click to expand...

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

MeanMachine1980 said:

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

Click to expand...

start by reading the vfd manual you are looking to buy and see what it says about sine filters.

Besides its probably cheaper to overrate your VFD by the 20-30% required by higher switching frequency and add du/dt filter to keep motor insulation happy.

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.

JST said:

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.

Click to expand...

By all means "The manual". Essentially ALL - even very old ones - are free for the download, online. Any question likely and many that are less-so is already answered - enclosure sizes, which filters, all of that and more.

Weirdness, even.

I just threw out an older Altivar 71 - didn't want to be bothered with the condition of its capacitors, going forward, and no longer had need of any VFD's anyway.

That one was spec'd and optioned to handle the full RPM band even of 400 Hz motors as well as 50/60 Hz.

I think that was probably uncommon, but doubt it lacked competition, either.