SPI communication error when High Voltage applied

[ikke1983]

Hi,

I just finished retrofitting an old CNC milling machine with VSD-XE drives.
Before installing the drives I tuned one of three drives on the bench with no load applied. Back then I already had a problem connecting to the drive when both High voltage and logic voltage where active, but by trying a number of times it would always connect in the end. Now the 3 drives are mounted in an enclosure on the CNC machine and I just can't get them connected with the GDtool. If I only apply the logic voltage it connects without any problems. I am testing the machine with the no load parameters that where stored in one of the drives, but now I really need to get them to communicate with GDtool to retune them and setup the homing sequence.
Does anyone have an idea on how to fix this, all the power and encoder cables are shielded, and the SPI cable doesn't run parallel to any other cables in the enclosure to minimize interference.

Thanks
Jonathan

[Xerxes]

This is caused by interference to communication (from high voltage signals such as PSU and motor leads). Few things that usually help:

-Ensure that cable shields are connected to FG as instructed in manual
-If you're using laptop, try disconnecting the laptop charger
-Use ferrite beads to suppress interference leaks/influences in cables (especially USB, motor and PSU).

[ikke1983]

I tried following things:

- 330 uF capacitor connected to HV+ and GND, directly on the drive, because the cables running from PSU capacitor to drive are longer than 30cm.
-2 ferrite cores on the SPI cable
-1 nF capacitor between pin 1 and 2 of the SPI connector.
- unplug laptop charger

All motor/encoder cables are shielded. The cable running from the PSU is not shielded, is this a problem?

I have 2 SPI cables, 1 with a 1nF capacitor between pin 1 and 2, and one without. The one with the cap doesn't work at all, even with the HV off.

After all this it still doesn't connect with the HV applied.

Can anyone help me with this?
Thanks
Jonathan

[Xerxes]

Thanks for the photos!

* 1nF caps should not be necessary if drive revision is 2.1 or later (capacitor is on board).
* CMD ribbon cable should be disconnecter when using USB cable (because of shared pins). Did you unplug the 16 pin cables?

[ikke1983]

Thanks for the help so far.

I did disconnect the ribbon cable, it didn't help.
Is there a reason to twist the HV+ and GND wires, to reduce parallel running distance? Or is this useless, since it's a clean (6.5kVA 3 fase transformer+rectifier with a 8200uF cap.) DC voltage? Or do ferrite cores on HV+ and GND have a positive effect on reducing noise or voltage spikes?

Thanks
Jonathan

[Xerxes]

Twisting DC cables gives lower inductance & lower emissions too, so it may be beneficial. Also ferrite beads (meant for noise suppression, not inductor type cores) also always help to reduce emission.

Also note that other interference sources near drives may affect communication. Have you tried unpowring other 2 drives while one is being used from GDtool?