Electronics for New Machine + Chinese Spindle + VFD

[mturneruk]

OK.... Thanks Neil.

Do you run your whole system from one physical plug socket or 2 - E.g. One for VFD and one for CNC ?

Why can i not use a 10Amp mains emergency stop button which cuts power in the AC mains line, thus doing away with the relay, transformer and all associated wiring....
e.g. Like this...

I want to keep things simple.
I really like the idea of having one physical kettle lead plug into my box, but I need to understand how many amps a VFD on full chat + 600Watt PSU driving stepper motor drivers will pull.
I have done some more research and a standard household plug socket is 13A max.

One things for sure is I need to check my consumer unit and understand my ring main better. I don't know what ring it's on or what else it's driving. Will do tomorrow.

[mturneruk]

Found some maths.... Not sure if it's right.

I (Amps) = P / V


So for my 48V power supply...
600 Watts / 48V = 12.5 Amps Potential...
Is that right. Something tells me it's more complicated than that..

[Clive S]

Found some maths.... Not sure if it's right.

I (Amps) = P / V


So for my 48V power supply...
600 Watts / 48V = 12.5 Amps Potential...
Is that right. Something tells me it's more complicated than that..

That is 12.5 A at 48 volts BUT you are using about 230V so 600/230 = about 2.6A

[mturneruk]

Ahhhh. Right. Thanks Clive.
That's better.

So lets say 3 amps from the PSU controlling stepper motors and i think i read 9 max from a VFD.. ?
So does that mean I could potentially run it all off one plug then with a 13a fuse?
Sorry for the dumbness on my behalf. I had to remind myself how a ground / fuse works earlier.

Getting there...

[Clive S]

Ahhhh. Right. Thanks Clive.
That's better.

So lets say 3 amps from the PSU controlling stepper motors and i think i read 9 max from a VFD.. ?
So does that mean I could potentially run it all off one plug then with a 13a fuse?
Sorry for the dumbness on my behalf. I had to remind myself how a ground / fuse works earlier.

Getting there...

I think you said that you read every word 5 times. It has been said several times that you can power your system from one plug. You really should take the advise from the good people on here all these questions have been asked lots of times.

[mturneruk]

Thanks !
Really getting somewhere now.

So it's decided that I need one power input into my enclosure and split it. Not listening to the bloke that told me I had to run two plugs any more.

So one side of the internal mains split will go to an EMI filter and then to the VFD.
The other side of the split will go directly to the 48V PSU.
One single all in one 10Amp chassis connector / fuse / power switch.
Easy. Job done.

Apart from Emergency stop.
So can anyone confirm why I can't just use an inline mains e-stop button. How does a relay do the job better ?

Thanks massively for your help.
Martin

[mturneruk]

Clive.

Just been trying to work out who the good people are!
I've had so much conflicting advice, it's hard to tell what's real and what isn't.
Found the answer to that now.

NJ. Thanks.
Neale. Thanks. I use those Network plugs to around my house. Will look out for the drop out. Wonder if the EMI filter might stop that.

Thanks
Martin

[mturneruk]

Thanks NJ...

I read that somewhere to, but what's the difference?
Surely if you cut the power to the VFD with a relay or with a switch your still cutting the power ?

Thanks
Martin

[njhussey]

Thanks NJ...

I read that somewhere to, but what's the difference?
Surely if you cut the power to the VFD with a relay or with a switch your still cutting the power ?

Thanks
Martin

The absolute correct way to do it is to use a relay to tell the software to say stop to the VFD, meanwhile a timed relay cuts the power after a second or so by which time the stop signal has reached the 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.