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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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Singing VFD
I have two different VFD's. Both turn a motor (different motors) just
fine. One is completely silent (TECO), the other one makes a noticeable and irritating whine (actually the motor makes the noise). The noise is coming from the PWM in the drive. I haven't tried every PWM frequency, but I have tried about a dozen. They all whine until I get up to 16kHz, where I don't hear it. This would be fine except that above 12kHz the drive is only rated at 80% (2.4HP); I intended to run a 3HP motor with it. The noisy VFD is a 3HP Cutler Hammer that I just bought. I have it set up for test with 4' of Romex connecting between the VFD and a 3HP motor. The motor is grounded to the VFD and has no load. I would appreciate suggestions on how to quiet the drive but keep the PWM frequency at 12kHz or below. Will a load change things? Will a different motor change things? Thanks, Steve Smith |
#2
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The motor is the problem. Chances are it is not a high quality motor and
this means the windings and laminations are not supported by resin impregnation as well as they could be. Even a high quality motor will make some noise, but it will be more of a hiss than a whine depending on the enclosure type and pwm freq. Randy "Steve Smith" wrote in message ... I have two different VFD's. Both turn a motor (different motors) just fine. One is completely silent (TECO), the other one makes a noticeable and irritating whine (actually the motor makes the noise). The noise is coming from the PWM in the drive. I haven't tried every PWM frequency, but I have tried about a dozen. They all whine until I get up to 16kHz, where I don't hear it. This would be fine except that above 12kHz the drive is only rated at 80% (2.4HP); I intended to run a 3HP motor with it. The noisy VFD is a 3HP Cutler Hammer that I just bought. I have it set up for test with 4' of Romex connecting between the VFD and a 3HP motor. The motor is grounded to the VFD and has no load. I would appreciate suggestions on how to quiet the drive but keep the PWM frequency at 12kHz or below. Will a load change things? Will a different motor change things? Thanks, Steve Smith |
#3
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On Sun, 10 Apr 2005 11:16:30 -0500, "R. O'Brian"
wrote: The motor is the problem. Chances are it is not a high quality motor and this means the windings and laminations are not supported by resin impregnation as well as they could be. Even a high quality motor will make some noise, but it will be more of a hiss than a whine depending on the enclosure type and pwm freq. Randy A quick check would be to pick up a used $5 motor and wire it up while its sitting on the floor and fire the sucker up. Gunner "Steve Smith" wrote in message ... I have two different VFD's. Both turn a motor (different motors) just fine. One is completely silent (TECO), the other one makes a noticeable and irritating whine (actually the motor makes the noise). The noise is coming from the PWM in the drive. I haven't tried every PWM frequency, but I have tried about a dozen. They all whine until I get up to 16kHz, where I don't hear it. This would be fine except that above 12kHz the drive is only rated at 80% (2.4HP); I intended to run a 3HP motor with it. The noisy VFD is a 3HP Cutler Hammer that I just bought. I have it set up for test with 4' of Romex connecting between the VFD and a 3HP motor. The motor is grounded to the VFD and has no load. I would appreciate suggestions on how to quiet the drive but keep the PWM frequency at 12kHz or below. Will a load change things? Will a different motor change things? Thanks, Steve Smith Leftwingers are like pond scum. They are green, slimy, show up where they are not wanted, and interfere with the fishing. Strider |
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R. O'Brian wrote:
The motor is the problem. ... I'm certainly no expert, but I have a little direct experience with this. I have a 3 ph motor and VFD on my drill press. It is the 2nd VFD. The first one sang, this one does not. Same motor, same wiring. Bob |
#5
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It isn't the motor I'll be using the VFD on. I suppose what I should do
is get some hydraulic oil and fire up the forging press with it (intended 3HP use). Gunner, I think your idea is how I got to where I'm at...except it was more than $5. Steve Gunner wrote: On Sun, 10 Apr 2005 11:16:30 -0500, "R. O'Brian" wrote: The motor is the problem. Chances are it is not a high quality motor and this means the windings and laminations are not supported by resin impregnation as well as they could be. Even a high quality motor will make some noise, but it will be more of a hiss than a whine depending on the enclosure type and pwm freq. Randy A quick check would be to pick up a used $5 motor and wire it up while its sitting on the floor and fire the sucker up. Gunner "Steve Smith" wrote in message ... I have two different VFD's. Both turn a motor (different motors) just fine. One is completely silent (TECO), the other one makes a noticeable and irritating whine (actually the motor makes the noise). The noise is coming from the PWM in the drive. I haven't tried every PWM frequency, but I have tried about a dozen. They all whine until I get up to 16kHz, where I don't hear it. This would be fine except that above 12kHz the drive is only rated at 80% (2.4HP); I intended to run a 3HP motor with it. The noisy VFD is a 3HP Cutler Hammer that I just bought. I have it set up for test with 4' of Romex connecting between the VFD and a 3HP motor. The motor is grounded to the VFD and has no load. I would appreciate suggestions on how to quiet the drive but keep the PWM frequency at 12kHz or below. Will a load change things? Will a different motor change things? Thanks, Steve Smith Leftwingers are like pond scum. They are green, slimy, show up where they are not wanted, and interfere with the fishing. Strider |
#6
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So I need to try a couple more things to know where the problem lies.
Thanks people, Steve Bob Engelhardt wrote: R. O'Brian wrote: The motor is the problem. ... I'm certainly no expert, but I have a little direct experience with this. I have a 3 ph motor and VFD on my drill press. It is the 2nd VFD. The first one sang, this one does not. Same motor, same wiring. Bob |
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On Sun, 10 Apr 2005 17:12:48 -0400, Bob Engelhardt
wrote: R. O'Brian wrote: The motor is the problem. ... I'm certainly no expert, but I have a little direct experience with this. I have a 3 ph motor and VFD on my drill press. It is the 2nd VFD. The first one sang, this one does not. Same motor, same wiring. Bob The Mitsubishi drives I have at home allow modification of the PWM frequency. Allen-Bradley drives I use at work do as well. Changing this frequency may reduce the noise generation, particularly if it moves away from a mechanical harmonic frequency. Pete Keillor |
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Steve Smith wrote:
It isn't the motor I'll be using the VFD on. I suppose what I should do is get some hydraulic oil and fire up the forging press with it (intended 3HP use). Oh, heck, if you're going to be running a hydraulic pump with it, you most likely won't hear the whine. I don't know of ANY hydraulic pump that could possibly be called quiet. But, if it still is a problem, an output reactor has a chance of helping. It filters the very square output waveform of the VFD to be much more rounded off. This should reduce the magnetic effects that are causing the windings to sing. Jon |
#9
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The second vfd is running at a pwm freq. that your motor does no respond to. Motor susceptibility to "singing" varies all over the place depending on motor size, insulation system, enclosure, mass, air gap, etc. There are many variables. Virtually all small vfd's generate very similar waveforms. The main variable is the pwm freq. This is user adjustable on most vfd's and is provided by the manuf. to help eliminate or suppress "singing", as many users think the noise is detrimental or annoying. The only other way is to install a reactor between the vfd and the motor. However, this is expensive, inefficient, and takes up space. Randy "Bob Engelhardt" wrote in message ... R. O'Brian wrote: The motor is the problem. ... I'm certainly no expert, but I have a little direct experience with this. I have a 3 ph motor and VFD on my drill press. It is the 2nd VFD. The first one sang, this one does not. Same motor, same wiring. Bob |
#10
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You know Jon, that finally occurred to me. It is getting pretty close
to solving the whole thing, except I was planning on also running a (2HP) lathe off of it (NOT hot switching them!). This may be sufficient; the lathe motor is enclosed, so I bet it will be pretty hard to hear 12kHz. Thanks, Steve whose head would be clearer if he wasn't bone tired from limping around after falling on the stairs Jon Elson wrote: Steve Smith wrote: It isn't the motor I'll be using the VFD on. I suppose what I should do is get some hydraulic oil and fire up the forging press with it (intended 3HP use). Oh, heck, if you're going to be running a hydraulic pump with it, you most likely won't hear the whine. I don't know of ANY hydraulic pump that could possibly be called quiet. But, if it still is a problem, an output reactor has a chance of helping. It filters the very square output waveform of the VFD to be much more rounded off. This should reduce the magnetic effects that are causing the windings to sing. Jon |
#11
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Jon Elson suggested a reactor as well (thanks guys). I thought about
this, but was worried about creating excessive voltages at the VFD. Has anyone actually used a reactor to filter a VFD output? Steve R. O'Brian wrote: The second vfd is running at a pwm freq. that your motor does no respond to. Motor susceptibility to "singing" varies all over the place depending on motor size, insulation system, enclosure, mass, air gap, etc. There are many variables. Virtually all small vfd's generate very similar waveforms. The main variable is the pwm freq. This is user adjustable on most vfd's and is provided by the manuf. to help eliminate or suppress "singing", as many users think the noise is detrimental or annoying. The only other way is to install a reactor between the vfd and the motor. However, this is expensive, inefficient, and takes up space. Randy "Bob Engelhardt" wrote in message ... R. O'Brian wrote: The motor is the problem. ... I'm certainly no expert, but I have a little direct experience with this. I have a 3 ph motor and VFD on my drill press. It is the 2nd VFD. The first one sang, this one does not. Same motor, same wiring. Bob |
#12
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Peter T. Keillor III wrote: On Sun, 10 Apr 2005 17:12:48 -0400, Bob Engelhardt wrote: R. O'Brian wrote: The motor is the problem. ... I'm certainly no expert, but I have a little direct experience with this. I have a 3 ph motor and VFD on my drill press. It is the 2nd VFD. The first one sang, this one does not. Same motor, same wiring. Bob The Mitsubishi drives I have at home allow modification of the PWM frequency. Allen-Bradley drives I use at work do as well. Changing this frequency may reduce the noise generation, particularly if it moves away from a mechanical harmonic frequency. Pete Keillor I've tried a number of frequencies with no effect. I should continue and try the rest. Thanks, Steve |
#13
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On Mon, 11 Apr 2005 20:03:48 -0400, Steve Smith
wrote: Jon Elson suggested a reactor as well (thanks guys). I thought about this, but was worried about creating excessive voltages at the VFD. Has anyone actually used a reactor to filter a VFD output? Steve Allen-Bradley sells line reactors for both the load and line sides of a vfd. Apparently they are useful with noisy power or long leads. I've never used them, but most of my motor leads are under 10'. The link below is their tech bulletin for line reactors. http://literature.rockwellautomation.com/idc/groups/literature/documents/td/1321-td001_-en-p.pdf Pete Keillor R. O'Brian wrote: The second vfd is running at a pwm freq. that your motor does no respond to. Motor susceptibility to "singing" varies all over the place depending on motor size, insulation system, enclosure, mass, air gap, etc. There are many variables. Virtually all small vfd's generate very similar waveforms. The main variable is the pwm freq. This is user adjustable on most vfd's and is provided by the manuf. to help eliminate or suppress "singing", as many users think the noise is detrimental or annoying. The only other way is to install a reactor between the vfd and the motor. However, this is expensive, inefficient, and takes up space. Randy "Bob Engelhardt" wrote in message ... R. O'Brian wrote: The motor is the problem. ... I'm certainly no expert, but I have a little direct experience with this. I have a 3 ph motor and VFD on my drill press. It is the 2nd VFD. The first one sang, this one does not. Same motor, same wiring. Bob |
#14
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I haven't tried every PWM frequency, but I have tried about a dozen.
They all whine until I get up to 16kHz, where I don't hear it. This would be fine except that above 12kHz the drive is only rated at 80% (2.4HP); I intended to run a 3HP motor with it. I believe that high switching frequencies are hard on the motor. Particulary if the motor is not designed to be used on VFDs. |
#15
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Thanks! If the final motor makes too much noise, I'll pursue a reactor
(probably at the scrap yard..) Steve Peter T. Keillor III wrote: On Mon, 11 Apr 2005 20:03:48 -0400, Steve Smith wrote: Jon Elson suggested a reactor as well (thanks guys). I thought about this, but was worried about creating excessive voltages at the VFD. Has anyone actually used a reactor to filter a VFD output? Steve Allen-Bradley sells line reactors for both the load and line sides of a vfd. Apparently they are useful with noisy power or long leads. I've never used them, but most of my motor leads are under 10'. The link below is their tech bulletin for line reactors. http://literature.rockwellautomation.com/idc/groups/literature/documents/td/1321-td001_-en-p.pdf Pete Keillor R. O'Brian wrote: The second vfd is running at a pwm freq. that your motor does no respond to. Motor susceptibility to "singing" varies all over the place depending on motor size, insulation system, enclosure, mass, air gap, etc. There are many variables. Virtually all small vfd's generate very similar waveforms. The main variable is the pwm freq. This is user adjustable on most vfd's and is provided by the manuf. to help eliminate or suppress "singing", as many users think the noise is detrimental or annoying. The only other way is to install a reactor between the vfd and the motor. However, this is expensive, inefficient, and takes up space. Randy "Bob Engelhardt" wrote in message ... R. O'Brian wrote: The motor is the problem. ... I'm certainly no expert, but I have a little direct experience with this. I have a 3 ph motor and VFD on my drill press. It is the 2nd VFD. The first one sang, this one does not. Same motor, same wiring. Bob |
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