Very strange noise from PCI-6229 with servo motor power on

[InteLink]

Dear all,

Currently I'm struggling on a problem:

The system include a IPC + PCI-6229 and a Rexroth servo motor(8kW).

When I power on the servo motor I get strange signal from each channel. When power off the servo motor controller every thing is OK.

I tried add bias resistor(2kΩ)/isolate the DC power, the problem still exist.

Below is the signal I collected:1k sampling rate20kbps

This kind of noise happened around every 2 seconds, it start with small then become big then come to zero.

Did any of you meet such kind of issue before?

[InteLink]

Is there anybody know this problem?

[GerdW]

Hi Link,

did you contact Rexroth when their servo motor introduces those noise (apparently)?

[Worle · Accepted solution]

Electrical noise can be difficult to find and fix.

I'd suggest doing the following things:

- Unplug things one by one until the noise dissapears so you know what is causing it

- Check that all noisy power cables (Motor power cables especially) are routed well away from your analogue signals, are screened and the screen is connected ground at both ends

- Make sure that the motor driver is as close to the motor as possible and as far away from your signals as possible

- Make sure you have followed any EMC requirements of your motor driver properly (This might involve putting chokes/filters on the power cable, specific types of screened cable etc)

- Make sure the common terminal of your DAQ hardware is properly connected.

There are literally thousands of things that might be wrong and without pictures of your setup it is difficult to offer more advice.

The PDF attached is a good guide to EMC best practices (There are also some others on the REO website)

Interestingly I had a very similar problem years ago that I never did manage to get rid of entirely (With a stepper driver) so I am interested if anyone else has any other input

[InteLink · Accepted solution]

Really appreciate for your help.

Final solution as below:

1. Add power isolation transformer at PC side.

2. Add signal optical isolator for all signals from test bench what ever it's current or voltage signal.

[InteLink]

Thanks for your help. Final summary as below: 1. The motor create inductive voltage and create differential voltage to daq throw torque sensor. Solved by add plastic coupling.