What switch type?

I have VFD(variable friquency driver) that outputs 3 phase 220V. I want to run two 3 phase motors off this VFD.(Not at the same time of course) VFD output has 3 wires + ground wire.

Which switch should I use to redirect current from VFD to one motor or another?

Thanks

I'd see if you could get a 3 phase switch with a contactor if the two machines are close and you throw the switch and it has an NC (normally closed) contact the turning ON one machine would make sure the other would NEVER turn on.

Basically turning on one of the machines would cut power to the other machine until the first was powered off

I tried to search for "3 phase switch" and "3 phase switch with a contactor" nothing came up. Can you find out what the "official" name or type for this switch is?

Thanks, Alex

I would use a reversing contactor & wire it up accordingly.

"Stephen Young" wrote: I would use a reversing contactor & wire it up accordingly. ^^^^^^^^^^^^^^^ You could run two conductors through a double-throw double pole switch, and hard-wire the third wire to both motors. Is that what you mean by a "reversing contactor?" IOW, are you suggesting a double-throw double pole relay (contactor), which of course would work?

It depends on the size of the motors and whether you ever want to switch them under load. If the motors are small enough, and you do not switch them under load, all you need is a three pole, double throw On-Off-On switch. Also known as 3PDT.

Check out McMaster item 8001K12 for high power switch, it mentions a

125v rating and I am noty sure about 240v rating. You can call them and ask. Do not just buy it without verifying.

I do have a suitable 3pdt switch for 30 amps, but I think that I would rather keep it for myself, for similar applications.

i

My motors are 2HP. I'll never switch them under load.

Please correct me if I am wrong... I need a switch with 9 terminals.

3 terminals to connect to VFD another 3 terminals connect to motor #1 the rest 3 terminals connect to motor #2

Switch in position #1 connects three terminals from VFD to three terminals of motor #1 Switch in position #2 connects three terminals from VFD to three terminals of motor #2

Am I right?

Alex

Ignoramus4546 wrote:

Yes, but it would be good to have a third, OFF, position.

You can get away with a relatively regular switch if you only switch it without load.

i

Three phase drum switch. Do NOT change the switch position while the VFD is on.

Jim

"Alex" wrote: (clip)Please correct me if I am wrong... I need a switch with 9 terminals. (clip) ^^^^^^^^^^^^^^^^^^ It might not be the most PROFESSIONAL looking setup, but I still think you could get by with a switch with SIX terminals. Feed two wires from the VFD to the "swingers" on the switch. Two wires out to motor one, two wires out to motor two, and the other wire from the VFD splits and goes to both motors.

that means that one machine will be energized when the switch supposedly turns it off. Not a very safe situation.

i

I'd add that by the time you're done fiddling with all these expensive plugs, sockets and switches, and then providing a way of relocating the speed and direction controls, it would be cheaper and far more convenient to buy a second VFD and be done with it.

That's what I ended up doing.

"Ignoramus26498" wrote: (clip) one machine will be energized when the switch supposedly turns it off. Not a very safe situation. ^^^^^^^^^^^^^^ Well, I wouldn't recommend working on the wiring with the VFD on. As far as running it is concerned, it's not more dangerous that having power to the motor while you are standing there using the machine. And we are talking about a machine that, by definition, is not being used, because the other machine IS being used.

"Jim Stewart" wrote: (clip) it would be

^^^^^^^^^^^^^^^^^^ The switch I am talking about is two pole, double throw--doesn't have to be switched under load--maybe $20. If you can put the VFD half-way between the machines where it can be reached, I don't see where all the expensive plugs and stuff come in.

Sorry, I might have gotten this thread mingled in my mind with another. There was someone who wanted 3 phase plugs and sockets for a VFD.

Everyone says this, but I've forgotten & done it without disaster. However, it was a 4Kw VFD driving a 1/2HP B/port M head at the time. Lotta excess capacity.

PDW

According to Leo Lichtman :

No -- a "reversing contactor" is two contactors mounted together, with interlocks so only one can be actuated at a given time.

But so far, in this branch of the thread, I have not seen the necessary warning that you should *never* switch between the VFD and the motor while the VFD is outputting power. It risks damaging the otuput transistors on the VFD with the switching spikes.

Enjoy, DoN.