3ph Plasma cutter wired backwards

[brightspark]

the vast vast majority of stuff is fine running backwards, at least for a while time while you turn it on, realise it's going backwards and turn it off to rewire it

anything that isn't will have a phase rotation relay on it to warn you it's wired backwards


my go-to for testing rotation it to turn it on and see

very technical no they wont

 

[knighty]

very technical no they wont

what won't ?

 

[brightspark]

what won't ?

be fitted with a rotation relay

 

[knighty]

be fitted with a rotation relay

why not? they're cheap as chips

anything I see that can be plugged in multiple places has them... transport refrigeration, steam cleaners, rental stuff etc. etc.

and that's just to idiot proof them

I have a meat drying machine (like a big oven you can walk around inside) it's fixed in place and made to be hard wired in, it has one...

I've seen them used a lot in a double glazing factory, machines which are fixed in place and hard wired in


I'm not saying EVERYTHING will have one (EDIT: ok I didn't say it's not everything... it's not everyhting)

 

[carbon]

anything I see that can be plugged in multiple places has them... transport refrigeration, steam cleaners, rental stuff etc. etc.

If you mean hot high pressure cleaners then the only one I’m currently aware of is the karchers, as they have to run one direction only to make sure the burner works. The fan/fuel pump is directly driven from the pump motor and if rotates the wrong way it doesn’t work. Lots of the rest don’t care which way they are connected as they use a separate single phase burner motor so the direction is always correct.

 

[Munkul]

We spent half a day with the "experts" trying to get a £70,000 homogeniser commissioned from new. It ran, but none of the hydraulic functions worked. Took a shift electrician to walk past and suggest checking rotation...
(having said that, the "experts" were utterly useless anyway)

 

[Screwdriver]

Having worked recently on some large thee phase installations (woodworking workshop), I can see how easily that can happen. Bit like fuse spec floating up over time, it only takes one owner to swap over a couple of phases to "fix" a backwards motor and over time the whole system can migrate!

I have seen a machine with a miswired socket being fed from a miswired plug. You only discover it when troubleshooting something else(!) because everything seems normal.

As has been said, three phase is relatively tolerant of phase reversals depending on where exactly that might occur, "tolerant" as in things still work but nobody notices. If you start swapping things around to be "correct" just be careful to start out from first principles and follow the chain all the way through the system. While you can sometimes "get away" with just swapping the odd phase to reverse a motor, if you start swapping power input feed, things can get dangerous pretty quickly if the system also provides balanced single phase loads.

I had a devil of a time with some lighting which had been (badly) installed running off a poorly wired three phase supply.

After checking with phase rotator it turns out that all my 3ph sockets are wired backwards, although the cutout is correct rotation, so there is a cross somewhere between the cutout and the sockets, and as a result my machines which were left in the unit when I purchased it such as the old Hypertherm are wired backwards to make them correct rotation at the machine.
I’ve just wired all the sockets for correct rotation and will rewire the machines to suit.

I’m glad I checked as I’ve got a 3ph lift on the way and would’ve wired it up assuming correct rotation at the socket

Err, yeah. Isn't that exactly what I just said?

You can thank me later.