Three motors, one VFD

silver_pilate

silver_pilate

Well-Known Member
After going through the trouble and expense of setting up my VFD in a clean box and running the remote controls for it for my KMG, I just didn't want the headache or bill from doing the same thing two more times. However, after adding a disc grinder set up on a 3/4 hp 3phase motor and another 2x72" grinder with a 2 hp 3phase motor, I needed an option to control the extra grinders.

I had the idea of using change over (rotary cam) switches. These types of switches are designed for use when changing over 3phase power from shore to a generator on big boats, but the switches are pricey. Pretty much all of the rotary cam selector switches that can handle the load were just too pricey to pull the trigger. So instead, I opted for plain on toggle switches. After some searching, I found these 3 pole, 2 position, screw post toggles rated at 30 Amps @ 250V. I ordered two of them and set up the switch box tonight.

It has the capcity to add another switch if I add a horizontal grinder in the future.

The input comes in from the VFD via 14/4 stranded wire and on to the first switch. When the switch is in one position, power goes to my 2hp KMG. When it is switched to the second position, power is sent to then input on the second switch. The second switch can be thrown to either control the disc grinder or my EERF 2x72" grinder. All the grounds are tied in to each other seperate of the switches.

My VFD is 2hp, and you can control anything at or under 2hp with it. I use the same controls and VFD to control all three of my grinders!

switchbox.jpg


Just thought I'd share. Thanks for looking!

--nathan
 
Wow! Nathan,you must have really done some thinking.:D

Just funnin with ya my friend.That is a good idea.I would have never thought of it.Thanks for sharing.

God bless,Keith
 
that's a good solution. I was going through that a few years back and looked at the rotary switches. They were pricey and I never did it. I'll have to look closer at your way now.
 
Nathan,

I thought long and hard about going that route with my set-up but never found the correct 3 pole switches and didn't want to go with 2 2-pole switches to accomplish the change between grinders.

I know that's not complicated to wire up but a wiring diagram and source with a part number for the switch would make a great addition to your website, hint hint.

Great Job ! Josh
 
Thanks, guys. Something to remember is to never throw the switches with the VFD running. In fact, on BF, Stacy suggested a safety cover, and that's a good idea.

You may want to look into larger gauge wire as well. I may be on the shallow end of 14/4's power handling capacity, though it's never even been warm to the touch after grinding, and it's been running my 2hp KMG for over a year.

--nathan
 
Josh, I got the switches from Mouser Electronics. They were part number 633-S832-RO (3PDT ON-ON HIGH CAP). They're NKK switches, and they are beefy for what they are with a very firm switching action. You won't trip these with an accidental bump. Something substantial would have to drop or bump on them to throw them. I picked up the box from Lowe's.

Wiring is very simple. There are nine screw terminals on the back of each switch. Basically your input to the switches goes to the 3 middle poles. Think of it like this: if your switch is oriented to you so that the action occurs from left to right, the three middle poles would be the ones running in line with you in the middle. Then your outputs go on either side, matching up the colors. If you throw the switch to the left, the right terminals are activated. Here's the wiring diagram. The switch I have is S832 on the second page.

http://www.nkkswitches.com/pdf/stoggleshighcap.pdf

Hope this helps :D.

--nathan
 
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