Why star ground????

[Kitwn]

If I were building from scratch I'd definately be going for the AXBB-E and UCCNC software combination rather than my current parallel port and cheap BOB combo. I have spent a lot of time fault-finding on that in the past and am not impressed with my failure to see the real cause before. But as that's what I have and I'm used to LinuxCNC and I've had it all working correctly in the past so I'm going to stick with it for now, though I have recently checked what the delivery time to Australia would be. The local supplier's markup equates to an arm and a leg so I would not use them. If this hobby turns into a money spinner in my retirement then an upgrade to a more reliable system would be a sensible investment.

Having seen the amount of noise present on the earthed case of my controller and everything inside it when the VFD is running I'd want a filter on the mains to protect everything else nearby. For $35AUD it's an easy fix (fingers crossed) though they want $40 for a simple aluminium box to put it in!! I've gone for a 10A two stage filter very similar in design to the one Muzzer linked to. RS are sending it from the UK so many readers on here could have one sooner than me if required. It's this one... https://au.rs-online.com/web/p/power...lters/1863517/

As I mentioned before there is no filtering on the earth cable and interference at high frequencies can escape via this route. There is no such thing as an earth at radio frequencies. Muzzer mentioned clamp-on ferrites as good for RF supression and one option for a filter I plan to test out is simply three ferrite rings with the live, neutral and earth wires into the VFD threaded through one each. This would prevent the spurious tripping of earth leakage breakers which can occur with conventional mains filters.

Kit

[Voicecoil]

There is no such thing as an earth at radio frequencies.
Kit

Well I was taught that this is not quite true, but only if it is a plane (which could be the walls of an enclosure as long as they're conductive and conductively bonded across any joints etc.) - as soon as you give it length >> width (i.e. a piece of wire) it has inductance and everything goes to rat shit, and smelly piles of it.

[Kitwn]

Well I was taught that this is not quite true, but only if it is a plane (which could be the walls of an enclosure as long as they're conductive and conductively bonded across any joints etc.) - as soon as you give it length >> width (i.e. a piece of wire) it has inductance and everything goes to rat shit, and smelly piles of it.

Absolutely true, but you have to take great care.

When I was a shiny new trainee at the BBC Transmitter Dept. back in the early 80s there were two demos that brought home the point I was wanting to make...

In the antenna fields of Daventry shortwave radio station the open wire feeders were supported on insulators hung about 3m up from tubular steel posts about 200mm in diameter which were firmly concreted into the ground. If you held a coin and ran it down the post under a live feeder you could clearly see sparks between the coin and the post.

At the Droitwich station there was a large neon bulb connected between the outer ground of a medium wave feeder where it left the building and the station earth strap which ran all round the inside of the building. It glowed a lovely neon pink and flickered in time to the music.

Happy days!