What is a good way to design multiple grinders on 1 VFD

Status
Not open for further replies.
D

David Metzger

Joined
Oct 8, 2010
Messages
109
I have a KMG and 9" disc grinder and 1 VFD. I would like to be able to reverse the disc grinder, and I would like to be able to add one more KMG. Can I use toggles or what kind of switches should I buy. I would like to keep it under $70-$100. All motors are 3 phase, 1.5HP.

I know this has been discussed but couldn't find much in a search.

David
 
Here's what I did with my setup. I currently run a disc grinder, KMG, and another 2x72" grinder off the setup with one speed control located centrally.

The main thing, you just don't want to have any way of sending power to two devices at the same time or you risk blowing your VFD.

switchbox.jpg


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 remote controls and VFD to control all three of my grinders!
Click to expand...

--nathan
 
I had considered going Nathan's route with a switch box in similar fashion but wanted to keep things simple to facilitate adding tools.

I wired a dryer outlet after my VFD and wired dryer cords to my motors and do have to unplug and re-plug to change tools.

Now that I'm set-up like this a $20 dryer cord is all thats needed to add another tool for VFD use.

I currently run my KMG, disk grinder, and surface grinder from my VFD

I'm hoping in the future to also add a horizontal grinder, integral grinder, buffer and if I ever decided to convert my mill to 3 phase (to eliminate using the pullies to change speed) I'll be good to go.

With the future in mind I decided using a switch set-up may get a bit complicated although it could be done.

045-1.jpg


Take care, Josh
 
David Metzger said:
I have a KMG and 9" disc grinder and 1 VFD. I would like to be able to reverse the disc grinder, and I would like to be able to add one more KMG. Can I use toggles or what kind of switches should I buy. I would like to keep it under $70-$100. All motors are 3 phase, 1.5HP.

I know this has been discussed but couldn't find much in a search.

David
Click to expand...


What kind of VFD?

You should / may be able to put the reversing switch in the VFD itself completely separate from the switch box as Nathan has setup.


I like the plug idea, no limit to the # of end devices and easy to plug a motor in to test it if buying a used motor.
 
+1 on what Josh said. I too wired my VFD to a female outlet. I just have cords with plugs on my KMG, Lathe, Mill, Horizontal Grinder and Disk Grinder. Just plug in what you want to use. Very simple.
 
I have one 220V outlet in my shop, and it's a good distance from where the grinders are (I have a REALLY big RV extension cord run to the VFD). That's why I went with the switch box route so I can seemlessly switch between grinders while working on something. The bummer is that my Evenheat oven also uses the one 220V outlet I have in my shop, so I cannot heat treat and grind at the same time :(.

In the new (smaller) shop, I'll have 2x220V outlets and a bazillion 110V outlets :D.

--nathan
 
I probably don't need to say this, but - do not switch from one to the other whith the VFD running.

If you want simple switching, use a 3PDT rotary drum switch rated for the HP of your motors. A suitable switch will run $35-75 on ebay.
Wire the VFD to the switch center poles, and put two 3PH sockets on the two out poles. Plug each device into a socket. You can easily change equipment at any time, as nothing but the VFD is hardwired.
 
Last edited:
I used to have plugs for each machine, but rewired for switches to switch seamlessly, as Nathan says, between grinders when working. The plug/unplug worked great but got old.

I set up my power hammer with a 3 phase motor, so now I have to add another switch.

I've just been using 3 pole, double throw on-on switches for three phase power switching. They have nine pins, wire the power in to the center row of three, and the power out to machines from the outer two rows of three. The switch takes the power from the center, and directs it to either of the outer rows. The lines of power are broken simutaneously by the switch when thrown.

Here is is link to such a switch, from McMaster with a 25A rating.
Part# 8001K41
High-Amp Toggle Switch 3PDT, on-on, 25 Amps, Quick-Disconnect
In stock at $12.58 Each

I wired my VFD with not only a run/stop, but a master power switch in the line before the VFD.
A 6-pin 3 pole single throw on-off toggle works well for simple power cutoff with 3 phase. Here's one at McMaster-Carr:
Part# 8001K39
High-Amp Toggle Switch 3Pst, on-Off, 25 Amps, Quick-Disconnect
In stock at $11.95 Each


To add a machine I'll add a switch by wiring from one of the outer rows of three pins on the first switch, to the inner row of three on the second switch. I can have a machine, or another switch wired to the other outer row of pins on the first switch, and could endlessly add a switch again to one side, and run a machine off the other side.

That may have been hard to understand. My apologies if this is so.
 
Those are some good ideas, Salem Straub, thanks for the parts numbers, searching the net for these parts give a ton of parts that wouldn't work. Any other ideas welcome. Dryer plugs - pretty cheap but a little tiresome to change.

Thanks everyone, David
 
Ok, so I have a couple questions before I order. Im not the best electrician. I have a KBAC 27D running my 2hp leeson motor on my grinder plugged into a single 220outlet in my shop. I want to add a 9" grinder and share the VFD. Do I need a 2hp motor for it to use with that VFD or can I use a smaller 1hp leeson motor. I seem to recall the VFD had a minimum hp rating, but maybe I am wrong. And because Im a little slow, I want to make sure I understand the wiring route. 220 to VFD. VFD to switch box that will have a switch, from McMaster with a 25A rating.
Part# 8001K41
High-Amp Toggle Switch 3PDT, on-on, 25 Amps, Quick-Disconnect that will control which motor has power? Does that sound right to yall?
 
I've run a 3/4 hp motor off my 2hp VFD with no trouble. Your basic path sounds fine, and that switch looks like it will work. Make sure your motor is fully stopped or at least not drawing power from the VFD before switching over, and you should be good to go.

--nathan
 
CWendling said:
Ok, so I have a couple questions before I order. Im not the best electrician. I have a KBAC 27D running my 2hp leeson motor on my grinder plugged into a single 220outlet in my shop. I want to add a 9" grinder and share the VFD. Do I need a 2hp motor for it to use with that VFD or can I use a smaller 1hp leeson motor. I seem to recall the VFD had a minimum hp rating, but maybe I am wrong. And because Im a little slow, I want to make sure I understand the wiring route. 220 to VFD. VFD to switch box that will have a switch, from McMaster with a 25A rating.
Part# 8001K41
High-Amp Toggle Switch 3PDT, on-on, 25 Amps, Quick-Disconnect that will control which motor has power? Does that sound right to yall?
Click to expand...

Keep us posted on how things turn out.
 
Cory, this is an old thread, and the OP hasn't posted on BF in two years. I will close this thread. If you need more info, best to start a new thread.
 
Status
Not open for further replies.
Back
Top