Please, I need any help or information on Servo Drive Electrical Noise Elimination

Hi everyone! XD

-- Very sorry for the long message. If you do not want to read everything, please read only my Hypothesis, and What I need section

I have a degree in Electrical Engineer but have only basic knowledge about Servo Drive, I have much more experience in microcontrollers and programming. The company I work for will be launching a product with a servo drive and I was responsible to make a PCB with a microcontroller to read some information from the Servo using RS485/Modbus. I thought the task would not be hard, but after one month struggling I have exhaust all my ideas.

At least I know what is the problem, a strong electrical noise in the Servo Drive that interferes and destroys my RS485 packages/frames

Let me explain what I have:
Xinje Servo Drive + motor 2.4 N.m 400W single phase 220V DS2-P4-AS
Servo - Wuxi Xinje Electric Co., Ltd.-Products-
Manual - [xinje.pl]

What I have done
I turned off and unplugged everything and let only the Xinje Servo Drive and the motor. I notice that when I put the servo in any control mode (position, speed, torque or even idle) and turn it ON, there is a very strong noise of amplitude of +- 4 V every 125 us in any Servo output. Please check the pictures and photos.

Pictures and photos
1) noiseRS485-ground.jpg - Measure RS485P to ground
2) noise-RS485P-RS485N.jpg - Measure RS485P to RS485N
3) noiseSwitchingPhaseV-to-Ground.jpg - Switching motor phase V to ground
4) noiseSwitchingPhaseW-to-V.jpg - Switching motor phase W to V


My hypothesis
Well, my conclusion was that the Servo is switching the phases every 8 KHz (therefore at every 125 us), since this is not a very good quality servo, the noise is propagating to every output. A friend of mine told me that this could be generating by something related to a term called "Hard Switching for the IGBT bridge", but if he is right the only solution is buying a servo from another brand.


Finally, what I need:
1) Do you think my hypothesis is right? Xinje engineers in China and Xinje sales person in my country think not.
2) Is there any way to solve this or should I tell my boss to buy another brand of servo? what brand do you recommend?


Do not need to read, but what I already tried in the last two weeks:
1) Design and RC or RL filter
Did not work

2) Using another Xinje Servo
Tried other two, same problem

2) Call Xinje Support
This was a total joke! a chinese girl from the technical support started laughing a lot because she could not speak any word in English.
I called twice and talked to two different persons. There is only one person in the support/sales that can write English, not speak. Ok, I cannot write nor speak English well, but I believe a company such as Xinje should have at least one guy that speaks well at the support.

Well, one "engineer" from Xinje said that I should used shield cables, I said I am using original Xinje cables. He also said the problem is in my PCB, even though I told him my PCB was totally disconnect from the circuit and I was measuring at the servo output.

Thank you for you time! Best Regards and I really appreciate any help, even if incomplete or if you not sure.