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Author Topic: NOISE!!!!!! Please help with shielding technique  (Read 3771 times)

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NOISE!!!!!! Please help with shielding technique
« on: March 03, 2008, 03:27:01 PM »
Hi all

Ive just finished building a lathe from scratch.I firstly build-ed the prototype out of wood to get all the dimensions right.

Been playing with the prototype turning wax for about 6 months without any problems, vfd and all.No special attention was given to shielding cables because I have not experience any noise related problems.

Consisting of the following components:

VFD and motor (3 Phase 380 Volts)
Rutex drives (2000 series)
Cambel breakout board and speed control
Servos
Transformer pack (From 220 Volt supply to lower voltages for the electronics)

Now for the fun part.......................

After converting the wood framework to metal all hell broke loose.

As soon as the VFD starts up every thing go's berserk.
I removed the VFD and 98% off my problem disappeared. The only other noise related problem I am getting is that the Z axis jumps about a 0.5mm when the motor starts up.

I really want to fit the VFD back so I need help in shielding all cables. My electronic knowhow is very limited.

So if some one can explain how to shield the following cables.

Shielding cable to be used has a stainless weaved shield.

1. From the wall ac socket to the transformer pack.

2. From the transformer pack to the Rutex drives.

3. From the wall ac socket to the breakout board.

4. From the Rutex drives to the servos.

5. From the breakout board to the Rutex drives.

6. From the speed control to the VFD.

7. From the forward and reverse relays on the breakout board to the VFD.

8.From the VFD to the spindle motor.

9. From the drives to the encoders.

If some one can explain to me fasten the shields and where not, and do I use the shield as ground or as 0 Volts or none at all.

Pretty Please any help will be appreciated.

Thanks
Deon
If A is a success in life, then A equals X plus Y plus Z.
                               Work is X: Y is play and Z is keeping
                                                             your mouth shut.

Offline Hood

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Re: NOISE!!!!!! Please help with shielding technique
« Reply #1 on: March 03, 2008, 03:54:57 PM »
Not an expert on this but then again I have never had any noise issues at all on any of the three retrofits I have done so far and hopefully the one I am working on at the moment will be the same. The shield is is just that and shouldnt be used as a 0V, connect the shield only at one end and try, as far as possible to connect all of your shielding to one single point on your control cabinet. Thats what I have done in the past and its worked for me. Both of my mills have used VFDs.
Hood
Re: NOISE!!!!!! Please help with shielding technique
« Reply #2 on: March 04, 2008, 03:19:52 PM »
Hi Hood

Thanks for trying to help.
In my quest for a solution I tried something tonight that really confused me.I kept every connection as it were and only physically removed the motor from the setup....eg. no physical contact between the motor and the rest of the machine.

Now I can start, run, stop and do dry runs without any problems .......... but picking the motor up while it is running and then touching the machine metal to metal with the motor all hell breaks loose again.

One thing I did manage to fix was the axis movement when I stopped and started the motor manually without the VFD.I have managed this just by shielding the wire from the switch to the motor.

Still battling for a solution.

Thanks
Deon
If A is a success in life, then A equals X plus Y plus Z.
                               Work is X: Y is play and Z is keeping
                                                             your mouth shut.
Re: NOISE!!!!!! Please help with shielding technique
« Reply #3 on: March 04, 2008, 03:24:53 PM »
Ground everything.
Motor case to earth. Make sure you have a good ground back to your service too.
And the drive chassi too.
And the machine base.
No ground loops.
RC

« Last Edit: March 04, 2008, 03:31:53 PM by Overloaded »

Offline Graham Waterworth

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Re: NOISE!!!!!! Please help with shielding technique
« Reply #4 on: March 04, 2008, 04:51:37 PM »
Is all the single phase electrics coming from the transformer or from the wall socket?

Take a single phase from the converter and use it to drive the other electronics.

The wood frame did not allow the phases to cross, metal will.  That could be your problem.

Graham.
Without engineers the world stops
Re: NOISE!!!!!! Please help with shielding technique
« Reply #5 on: March 05, 2008, 09:56:48 AM »
A good point. I've seen no end of nuisance caused by lots of single phase equipment running together on different phases. It all stopped when we got our customer to fit it all to one phase only.

I've got all my 240v control gear, contactors, lamps etc. and 9V control supplies running off L1. L2 and L3 only do motors. So far i've had no problems doing anything despite pretty crappy shielding.