Quote Originally Posted by Cube3 View Post
I had very similar problems until I did this.

https://www.youtube.com/watch?v=DJfiOqaeFDg

Simon
Simon,
Apologies for not getting back to you earlier, I got somewhat sidetracked away from the original reason for this thread.
That's a very interesting video and I especially like the improvised current transformer for investigating noise, I hadn't seen that trick before but it will be useful in future. As I've discovered the VFD is not to blame (yet!), it's enabling the motors that generates the noise I'm investigating at the moment. Once that's been quietened down I can then see if the VFD adds any problems. It wasn't an issue when I had NC microswitches for limit sensors so my fingers are crossed on that one.