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Author Topic: VFD Noise  (Read 1081 times)

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VFD Noise
« on: November 17, 2017, 11:07:53 AM »
Hi
Been getting a tripped emergency switch every half hour or so while running my machine. I know I have some noise interference so decided to try and isolate it. I ran my machine for a couple of hours just cutting air without the VFD and spindle running no tripping so I am confident there lies my problem. My question at one point while running the g code maybe 45 minutes into the program everything stopped no emergency trip just stopped could not move anything even by rewinding g code ended up shutting down the computer and restarting ran the same gcode for a couple hours with no problem was checking other noise sources florescent lights, my water pump for the spindle, dust collection. just  the VDF trips it will work on that. any idea why it would just stop.

I read this forum everyday for a couple years, and have learned a great deal from all you guys
Thanks for sharing
Bill
Re: VFD Noise
« Reply #1 on: November 17, 2017, 12:18:28 PM »
Bill,
Show us a picture of your control panel wiring and we may be able to help easier.
Re: VFD Noise
« Reply #2 on: November 17, 2017, 12:34:03 PM »
Hi,
electrical noise is both radiated and conducted. The high frequency currents in the VFD output are very likely to be radiated to other circuits.
The electrical demand of the VFD will induce voltage fluctuations on the 230V input an can be conducted into other power supplies/devices.

As an experiment try plugging in your VFD into a separate socket to your PC and machine supplies.

Craig
My wife left with my best friend...
     and I miss him!
Re: VFD Noise
« Reply #3 on: November 17, 2017, 02:21:35 PM »
Hi
My VFD is plunged into a separate circuit from my control box, if I am understanding you correctly. From what I have read on the forum over the years is that the spindle wires and power to the VFD should not be in proximity to the limit switch wiring. while I am using shielded cable on everything I thought I would try moving The VFD and the spindle wire to see if that might be my problem.
Thanks for your interest
Bill
Re: VFD Noise
« Reply #4 on: November 17, 2017, 03:22:39 PM »
Hi,
yes you are advised to separate your VFD wiring from signal wiring. This is a strategy to reduce RADIATED interference but does not address CONDUCTED interference.

You say that you have your VFD in separate 230V outlets but what degree of electrical separation is there between the outlets?

In New Zealand at the current time in the province in which I live there has been a major upsurge in agricultural irrigation much powered by multi hundred kW
VFD pumps. The electrical noise which is reflected into the power grid is causing major issues. The local power companies are having to insist that line reactors and
filters be used. The farmers hate it, line reactors and filters can cost tens of thousands dollars.

Small VFDs such as we use are not likely to come under official scrutiny but they do 'pollute' the electrical supply in their vicinity. My suggestion relates to the fact
that many hobbyist CNCers pollute their own power supply and then wonder that their sensitive electronic systems go cranky.

Try running your VFD, or alternately your machine controller/PC, from an extension lead well separated (physically an electrically) from the other.

I have given similar advice to others and about half have found that it solved the problem. Some have gone on to buy line reactors per VFD manufacturers recomendations
to achieve a permanent solution.

Conducted electrical interference is often overlooked. You could spend many hours and dollars trying to stop radiated interference and achieve nothing. Try the conducted
noise experiments until you are 100% positive that it is not the fault before trying the radiated noise reduction strategies.

Craig
My wife left with my best friend...
     and I miss him!
Re: VFD Noise
« Reply #5 on: November 17, 2017, 05:34:19 PM »
Hi
My VFD and spindle are three phase all separability fused and lines in the building. My PC and control box are single phase and separate also.
Bill
Re: VFD Noise
« Reply #6 on: November 19, 2017, 01:54:58 PM »
Hi
Thanks for your interest, I don't know a lot about interference, You mentioned conducted interference could this be a possible cause in my case the 3 phase power for my shop comes into the building as a separate line that is used for my spindle and the VFD. the power for my PC and control hardware in single phase and again comes into my building as a separate line they are both isolated and not shared . As I get into trying to find my noise issues would this be something I would add to my list of possible causes.
Bill
Re: VFD Noise
« Reply #7 on: November 19, 2017, 02:51:15 PM »
Hi,
I suspect not. It seems unlikely that you have seperate single and three phase supplies.

More likely you have one three phase connection into the building with a single phase picked off for your
single phase circuits. It is not impossible therefore that noise on the three phase circuit is being impressed on
your single phase circuit. It seems more likely that you have a radiated interference problem rather than
conducted interference.

Craig
My wife left with my best friend...
     and I miss him!