VFD interference problem

[eurikain]

Yes, the building earth goes to the electric company I believe. Standard setup here. I am actually not using any box anymore, it's all out of the box, screwed on a fireproof plate (not metal). I am sorry I haven't posted pictures. Here it is:

The X motor plates have been unmounted to prevent the gantry from twisting. The fireproof board is out of the box for easy access and testing.


All relays are not wired, there is no e-stop, no reset button, no contactor, not fans, no switches (only a switch on the power cord extension), no 24V power supply (Earth and Neutral are daisy chained with the 5V PSU, but there is no Load going to it as you can see).


So, here is what happens:
1. drivers powered, Mach3 in reset mode, motors disabled, VFD powered, spindle off
2. click reset in mach3, motors are powered, enabled and locked
3. I can jog fine on each axis
4. press RUN on the VFD, spindle starts spinning right away. half a second after pressing RUN, I can feel (with my hand) and hear the motors move a few steps (ike 2-5 I would judge by feeling). Obviously I can't put my hands on all motors simultaneously, so I try one by one (the VFD is wired separately so I can carry it around with me).
5. press STOP on the VFD, same thing, right before the spindle stops spinning (so I would say in the lower frequency, around 500/1000 RPM), the motors move a few steps.

There are two parameters to the noise:
1. the time offset between the moment I press RUN or STOP. I guess this depends on the time it takes to get to the problematic frequency.
2. the number of uncommanded steps the motors move

If I press RUN, then wait until the spindle reaches the desired speed (100Hz), then press STOP, wait until it stops, and repeat this process a few times, I would say the problem occurs 7 times out of 10. The number of uncommanded steps and the time offset are always random.

Hope you can see things better now :)

Cheers,
G.