Why star ground????

[Muzzer]

"Conventional wisdom" is split. Some recommend only grounding one end of a screen, others recommend both. In practice, there's no right or wrong answer and I've found cases either way where one works and the other doesn't when I've done EMC testing on professional VFD installations.

Most VFDs are sold without a mains filter yet they need one. The reason they don't usually come with one is because it's not possible to define one that will meet the requirements unless you know the exact details of the installation, not least how the motor will be connected up. So many people just connect them up without a filter, then have the devil of a job trying to figure out why they have noise problems.

Here's the recommended filter for the 4kW Yaskawa VFD. It's probably a bit OTT for a 3kW VFD but gives you an idea what to expect. The VFD itself mounts on top of the filter using the 4 threaded holes - very neat - and the wiring provided is even the right length for the model of VFD it's intended for - in this case the 4kW V1000. There's no guarantee this will meet the requirements out of the box but it's likely to get you close if it doesn't.
https://inverterdrive.com/group/EMC-...8-40-07-V1000/

For noise in the 1-10MHz region, the clip on lossy ferrite clamps are great. Even better, they don't require you to disturb the wiring and can be used on both mains and signal wiring. This sort of thing. Genuine TDK ones would be good:
https://www.ebay.co.uk/b/clip-on-ferrite/bn_7024808499

[JAZZCNC]

I think half the problem with noise issues is how people route wires in the box and on the machine, the other half is because they try to do things on the cheap and use components like cheap £5 Bob's using the parallel port with long and cheap cables.

I've lost count of how many control boxes and machines I've wired/built over the years (I've done 6 in the last 2 wks) and I very very rarely suffer from noise issues on stepper based machines, servo based can be a little more touchy but still very minor and rare. I don't fit any filters or ferrite rings on anything, I can place VFDs inside and outside control boxes and this is mostly using cheap Chinese VFDs like Huanyang, Fuling, etc. Now, this isn't because I'm a master electrician or Wizzard or anything it's because I use good components and good cable management along with good wiring practice.

I don't understand why people try to cut corners by using cheap £5 Bob's and the parallel port these days when a decent Ethernet motion controller like AXBB-E which includes the BOB costs approx £200 with the license file. Now, I know some are going to say £200 is a lot of money compared to £5.!! . . . But this is a false economy.

The first time the machine throws a bitch fit because of noise while cutting all your savings can be blown as it breaks the cutter, wrecks the material not to mention time wasted, esp if doing this for a living. Even if you are doing this as a hobby it doesn't take long to recover the costs of doing things correctly. Not to mention the stress and frustration it will save.
Many people spend more money trying to chase the noise away than doing it right the first time.! Then throw in the performance increase and reliability and it just doesn't make sense not to do it.