Help on isolation switch fit two circuits/power supplies

[Nathcr3708]

Hello,

I have two circuits in my enclosure 1 is 240vac at 20A and the other is 240vac with 16A. I'm putting my vfd and spindle on the 16A and my controller, drives etc on the other.

My question is this...
I have my rcd box and I've used two mcb's connected them up to two double pole mcb's in my enclosure. How do I go about placing an isolation switch on my enclosure to turn off power to both circuits?

I have contactors for 240vac do I place 1 on each circuit after the 2 pole breakers and wire an isolation switch through them if so how do I do that?
And if that's not the correct way how do I do it?

I want to put an isolation switch for both circuits before they get to the equipment, and then I'm hoping the Estop will be what it says on the schematics I.e through the controller to stop the vfd and the moters through the controller. That should work right? Even if there on seperat circuits the controller should tell the vfd and motors to stop running if im correct!

Would appreciate the help as I need to know what to get tomorrow when I go to the wholesalers for my equipment.

Kind regards,
Nathan

[ShawnM]

Can I ask the simple question of "why" are you doing this?

[Gary Campbell]

A few observations:
In my experience, usually the spindle would be on a higher amperage circuit than the control
Is there a reason to not use a single, higher amperage circuit?
I prefer using a load break switch, usually door mounted as an added safety feature
Your spindles VFD and the drives power or power supply should be controlled by contactors on an estop safety circuit, the low voltage system power supplies should not
Power routing is 1) thru load break (main) switch, 2) distribution blocks, 3) circuit breakers, 4) contactors where needed, 5) individual devices

[Nigelo]

As Shawn correctly asked "Why" and in addition to Gary's comments:

For correct electrical coding, you need to obtain the advice from a qualified UK "sparks" (Electrician in UK parlance). In the UK, the declared voltage and tolerance for mains electricity supply is not 240vac but 230vac -6%, +10%. This gives an allowed (by Statute) voltage range of 216.2 volts to 253.0 volts.

If this was my project, I would definitely not place the VFD inside the same cabinet as the Controller and drives. Apart from any other consideration you are inviting EMI. Not insurmountable but why take the chance? In any event, I would definitely not be supplying 2 separate mains feeds into the same cabinet for safety reasons.

Given a separate metal enclosure for the VFD, with its own mains supply, your controller cabinet appears to require a max current of 4 amps @ 230vac calculated at 210w for each of your 4 PSUs (max output apparently required by each motor 3.5A @ 60vdc) . Strictly subject to your Sparks' advice, you could then run both cabinets/enclosures from the same single 20A breaker as your VFD / Spindle appears to require approx 13A

One final point, are you confident in your choice of PSU? All have the same model number S-350-60 BUT 1 states 6.8A @ 230 vac whilst the other 3 state 5.85A. Then again, they are Chinese so its anyone's guess.

[Nathcr3708]

I understand where you are coming from, al.ost all have one circuit or power supply.

The PSUs were supplied with the kit. My plan over time is to swap out the Chinese stuff for British or German made parts.
I only thought two power supplies made sense I'm OK at electrics but with the spindle and vfd I thought if there's a surge atleast it won't hit my other equipment.

So your saying run them on the same circuit I can change the circuit to a 40A circuit. I just need to understand how with one circuit can I dedicate seperate parts I.e the control unit the drivers and all equipment from the vfd and spindle. How would you go about doing this? Why should I put the vfd in a seperate box I've seen almost all enclosures online with the vfd in the same enclosure.

I'm just a little confused like I said I'm happy to use one circuit I just need to know how I would I.protect everything from the vfd and spindle from everything else?

[Nathcr3708]

Just so you know I'm providing my machine not from.plug sockets but straight from my RCD

[ShawnM]

I guess it would be helpful to know what size spindle you'll be running. It must be huge if you think you need a 40A circuit.

I have an entire CNC router using Clearpath servos with a small 5HP air cooled spindle on it running on a single 30A breaker using 240 VAC from my panel. Everything runs off this circuit including the CNC PC and monitor.

[Nathcr3708]

The machine will not be moved so I wanted to keep it from the plug sockets due to surges.
I ran my old cnc machine off a nano v3 control board connected to my pc and it was a simple set up.
Now I have to do,
Enclosure,
3kw huanyang vfd,
3kw spindle,
Pc cooling system for spindle,
4 350-60v PSUs,
4 nema 34 motors 1600Oz,
4 drivers that use 5v,
Lubrication/cooling unit,
12v psu,
Acorn 4 control board,
Acorn psu,
Pwm laser,
Dust collection unit, but do not have yet so will be added on at a later date so I will be using the workshops vacuum system.
Hp pc,
1 touch monitor,
1 35" tv/monitor, so I can have seperate windows open at the same time so I can see where I'm at on the print and also have the capability to work on the other monitor for other projects.

My original plan was 2 circuits one 16Amp for the vfd and spindle I know the vfd is rated at 13A however I added 3A more amps due to possible surges.
Then I was putting everything else on a 20A for everything else. However the is problems when it comes to.power isolation etc.

Now you have said its fine to put that on one circuit without constantly tripping, I'm hapoy with one.
I Have contacts, thermal overload relay, emi filter, dc fuses Estops, isolation switch and all my cable ready.
What I would like to know since you already have your set ups complete what Amp circuit you thing is good!
I could really use a bit of help and advise.
Maybe a wiring diagram?

I would like to also have controls of stop and start and also have some controls for the cnc router like most people have with indication lights.

My cnc machine which I built is 6ftx4ft.
I really appreciate your help.

[tblough]

Gary has already stated the proper technique. You want a SINGLE power entry point to your machine. This is directly attached to the main disconnect. It is then divided to a series of breakers/fuses sized for the different loads. The wiring is sized to carry the amperage of the last upstream fuse. Fuses are sized to protect the downstream load.

Here's a schematic i did for a lathe refit - https://centroidcncforum.com/download/file.php?id=1583. It's split phase 240V, but the concepts are the same.

[ShawnM]

It's highly doubtful that your 3KW spindle/VFD package will draw anywhere near what you are thinking. We or should I say "I" cannot suggest a circuit breaker size for you, this is something you'll have to calculate from your components.

It's also not advisable to have your dedicated CNC PC doing "other things" while it's working but it's your machine. Just food for thought.

Here's a link to all the Centroid wiring diagrams you could ever want. Just use the search box in the upper left to find what you are looking for. There are lots of "generic" diagrams for you to follow.

https://www.centroidcnc.com/centroid_di ... .php?term=