Electronics for New Machine + Chinese Spindle + VFD

[Neale]

Don't get too wound up about the total consumption via the mains plug. The VFD is rated at 2.2KW. That means that it is capable of delivering 2.2KW, not that it actually takes that power all the time from the supply. The chances are that you will hardly ever, if at all, run the spindle at those kinds of levels. So most of the time the VFD will be drawing much less. Similarly, a 600W PSU is capable of delivering 600W, not that it will draw this all the time. Again, chances are that you will hardly ever be running at these levels. However, worst case, VFD draws 2.2KW, PSU draws 600W, total 2.8KW. For rough estimating purposes at normal mains voltages (and it keeps the numbers easy) assume 4A draw per KW. So, that's 4*2.8 = 11.2A. A 13A plug and socket should be able to deliver this continuously (this is electric kettle/washing machine heater kinds of loads, or 3-bar electric fire). That's why you can run any normal size CNC router off a standard 13A socket. The issue about separate supplies for VFD and the rest of the electronics is that the VFD probably generates the most electrical noise, some of which is fed back into the supply and hence to anything else on the same ring circuit. If you have two sockets in the workshop fed from separate ring mains, then it's best to use those to keep VFD separate from everything else. However, that's very unlikely and if you have a double socket, then both sockets will be on the same ring. So it doesn't matter if you use separate plugs, or single cable into the box and then split it - they are still on the same ring main.

My machine has been running happily like this ever since I built it and I have never had any problems. I use an Ethernet-over-mains adaptor to get a network connection into my workshop (useful for copying files from my main machine where I do CAD/CAM things) and that works well until I switch on the VFD. Then - nothing. That's due to noise injected back into the mains. However, I don't need the network while I am machining, so no problem in practice.