I have VFD(variable frequency 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

Alex wrote:
I have VFD(variable frequency 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

Alex wrote:
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?

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:
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

On 14 Mar 2006 16:31:39 -0800, Alex wrote:

I have VFD(variable frequency 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

In article .com, Alex says...

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

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

Jim


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"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.

jim rozen wrote:
In article .com, Alex says...


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


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

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
cheaper and far more convenient to buy a second
VFD (clip)
^^^^^^^^^^^^^^^^^^
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.

Leo Lichtman wrote:

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

cheaper and far more convenient to buy a second
VFD (clip)

^^^^^^^^^^^^^^^^^^
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.

In article , jim rozen
wrote:

In article .com, Alex
says...

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

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

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 :

"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?

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.

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--- Black Holes are where God is dividing by zero ---

"Alex" wrote in message
oups.com...
| 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

Try "reversing motor starter" and then rewire it so that it doesn't
reverse the phases. They switch power between them but lock the other side
out so that they can't both be operated at the same time. Most have a lever
between them as a backup to the electrical control circuit, since idiots
sometimes tend to wire/rewire them. Firing both contactors at the same time
is likely to be a rather dramatic event as it shorts two phases without an
overload.
Used on ebay is good. If you feel so inclined, it would be good if each
motor has its own overload and can drop out its own contactor when there's
an overload. You might want some help doing this, but the actual buttons
you need for the task are really simple.
Make sure the contactor is equal to or better than your motors, and that
the overloads (assuming you use overload heaters instead of a magnetic
circuit breaker type) are proper for your motor, and since they're cheap,
worth having spares on hand.