A/B switch for VFD?

[Troy H]

Is there a switching box available to use a single VFD on two different motors? It seems that it would be a simple enough device, but I haven't been able to find one. Does anyone have any experience with them if they do exist?

Thanks

 

[silver_pilate]

I made one for my KMG and disc grinder. You just have to make sure the switches you use are rated correctly for your motor's amperage draw and voltage. You can get dual toggle switches with on-off-on positions. There are heavier duty rotary switches out there as well.

--nathan

 

[PIndelicato]

I made one for my KMG and disc grinder. You just have to make sure the switches you use are rated correctly for your motor's amperage draw and voltage. You can get dual toggle switches with on-off-on positions. There are heavier duty rotary switches out there as well.

--nathan

Nathan, I've been thinking about this recently. Do you have any specifics about the kind of switches you used and/or any pics of the wiring and your setup?

 

[silver_pilate]

Paul, I'll see if I can take some. I used switches rated at 6 amps, 250V as my KMG motor's peak draw is 5 amps. I believe this is the switch I used:

http://www.radioshack.com/product/index.jsp?productId=2062514

I had to use two switches to accommodate the three powered legs to the motor. Also, make sure your wiring is secure, you don't want you connections to come loose or short. With these switches, power comes in on the middle post and is distributed on either side.

A better choice is a three position rotary cam switch. I'm on the look out for one. They're rated for higher amps and can accommodate all your leads on the same switch, but they're a good bit more expensive.

With the setup I used, I just make sure I turn the power to the motor off, let the motor stop, and then throw the switches. That way there is no juice going through the lines when I switch. Also, I mounted the box for the switches securely so as to not jostle the connections.

--nathan

 

[PIndelicato]

Thanks Nathan, if you take any pics I'd love to see them. I'd really like to have a disk setup, but I sure can't afford buying another VFD and brand new motor to do it.

 

[JTknives]

I don't see why you would need a 3 pole switch or even need two switches. in order for power to flow you need a hot and a neutral line. just one does nothing at all. so how i would do it would be like such. get a DPDT "double pole double throw" switch and wire it like i have drawn in the drawing below.

 

[65535]

That's a very clever way to wire it, I like it.

 

[DAMNENG]

Guys -- All the VFDs I have come in contact with (In real life I work with electronics and electrical controls) have a three phase outputs. All three phases are hot! While it is OK to connect the ground wire (this would be a forth wire connected to the ground lead on the VFD) to both motors at the same time, I suggest you switch all three phases at the same time and only with the VFD in the off position. To do this you need a three or four pole, double throw switch. While you only need three poles, you will probably find four pole double throw switches easier to come by than the three pole versions. You only use three of the four poles. You either need a "Break before Make" switch or a "Center off" switch. This prevents having both motors connected at the same instance should you accidentally hit the switch or have a brain fart and flip it to the other motor position. The three leads coming from the VFD to the switch go to the center row of terminals with one motor connected on each side. To reverse the rotation of a motor, swap any of the three leads.

Jim Arbuckle ABS JS

 

[Josh Dabney]

I debated long and hard about this very question. I just decided to wire a 4 prong dryer outlet after my VFD and put dryer cords on my Kmg motor and disk motor.

I REALLY wanted switches to change between motors but it honestly takes 5 seconds to un-plug one motor and plug in the other.

Tapering tangs is a good example. I hollow the tang on the contact wheel then hog the flats on the tang on the flat platen then grind the tang on the beveled disk.

It takes longer to change belts or change from contact wheel to platen than it does to go from KMG to disk.

I felt like I was settling with the outlet and plugs over hardwired switches but in actual use I'm VERY happy with this set-up.

Just my 2 cents

Josh

 

[blindhogg]

Jt
While that would work for 110v or even single phase 220v but as Damneng mentions all three lines of a vfd are hot. so wiring it up that way is probably a no no. I would just use a 4pdt switch as damneng mentions. I just bought a bunch from surplus center and am pleased with them, they would work in this application and they are only $5.

https://www.surpluscenter.com/item.asp?UID=2108011622085259&item=11-3221&catname=electric