Vfd

DC KNIVES said:
Rob use's VFD's not speed controllers, and the link you gave to the AC speed controller will not work on the OP's motor.That speed controller is for fans and blowers, totally different kind of motor.Dave
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This picture from his web site is of a KB Penta Drive, which is a speed controller.

I was not aware of the AC drive limitations, just looked for an AC speed controller. Apologies.
 

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Well you can use a speed control for an AC motor that runs fans, blowers, pumps. An application where the torque requirement is greatly reduced with speed. A grinder requires at least as much torque at lower speed, therefore you need to maintain torque. That requires a DC or 3PH AC motor with a proper drive.
 
WCK, on my grinder I use a variable pulley setup.(NOT step pullies) The motor and pullies reside in the enclosed base, with a crank coming through the top surface to adjust speed. I don't know why you don't see others using this setup. It gives me speed adjustment of approx. 1500sfpm to 5600sfpm. I don't recall offhand the name on the pullies, but is is something like Vari-Cone. Several manufacturers make this type of speed control.
I previously posted photos and description of my setup.
Good Luck
Alden
 
I just bought a Baldor 2HP 3ph motor off of ebay for $90 shipped. I then purchased this drive. I'm in the new drive and motor for under $250. I am upgrading my 1HP setup with this. I will use the 1HP/drive from my grinder for a disc sander. May be an option for you?
 
I just asked Rob (rfrink) about this today (ordered a 3 HP motor with my KMG).

If I understand correctly, the VFDs drop the power on 3 phase motors by about a third in the process of powering them from single phase 220. So, if you have a motor rated at 3 HP on 3 phase power, you get about 2 HP out of it.

In his pricing, Rob sells the motor as rated by the VFD, and not as rated on 3 phase power. So the "3 HP" motor he offers would really be something like 5 HP if driven with 3 phase.

So, if you end up comparison shopping for motors, make sure you're comparing 3 phase ratings with 3 phase ratings OR VFD-driven ratings with VFD-driven ratings. You may find his prices are even better than expected!

Tait
 
VFD's will run single and 3-phase motors. The advantage to using 3-phase motors is they are cheap to buy and cheap to operate. Some VFD's are biult to accomodate "only" single or three phase, while others can do both.

DC motors can be run on a speed controller. AC motors pretty much need a VFD.
 
tait said:
I just asked Rob (rfrink) about this today (ordered a 3 HP motor with my KMG).

If I understand correctly, the VFDs drop the power on 3 phase motors by about a third in the process of powering them from single phase 220. So, if you have a motor rated at 3 HP on 3 phase power, you get about 2 HP out of it.

In his pricing, Rob sells the motor as rated by the VFD, and not as rated on 3 phase power. So the "3 HP" motor he offers would really be something like 5 HP if driven with 3 phase.

So, if you end up comparison shopping for motors, make sure you're comparing 3 phase ratings with 3 phase ratings OR VFD-driven ratings with VFD-driven ratings. You may find his prices are even better than expected!

Tait
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Static phase converters only give you 2/3 of the motor power.
VFD's will give full motor HP. If the VFD is rated at single phase in/3 phase out your good to go provided the VFD matches the motor.

If the VFD is 3 phase in/3 phase out you need to derate the VFD. In other words, if you have a 2 hp motor you would need a 4hp VFD. You would then get the full 2 hp from your motor.

Michael
www.adammichaelknives.com
 
89diesel said:
VFD's will run single and 3-phase motors. The advantage to using 3-phase motors is they are cheap to buy and cheap to operate. Some VFD's are biult to accomodate "only" single or three phase, while others can do both.

DC motors can be run on a speed controller. AC motors pretty much need a VFD.
Click to expand...
VFD's will only run 3 phase motors. You can run them with single phase power but it must be a 3 phase motor.
 
Mark, for what it's worth, I run a VFD and 2hp 3 phase 3600rpm motor with no troubles. It's not too fast. You just have to choose the correct sheave sizes to get the grinder input shaft rpm's you want.

--nathan
 
tait said:
I just asked Rob (rfrink) about this today (ordered a 3 HP motor with my KMG).

If I understand correctly, the VFDs drop the power on 3 phase motors by about a third in the process of powering them from single phase 220. So, if you have a motor rated at 3 HP on 3 phase power, you get about 2 HP out of it.

In his pricing, Rob sells the motor as rated by the VFD, and not as rated on 3 phase power. So the "3 HP" motor he offers would really be something like 5 HP if driven with 3 phase.

So, if you end up comparison shopping for motors, make sure you're comparing 3 phase ratings with 3 phase ratings OR VFD-driven ratings with VFD-driven ratings. You may find his prices are even better than expected!

Tait
Click to expand...

There isnt any noticable power loss with a VFD...as stated with someone else, phase converters lose 1/3hp...

I have the Teco 1hp VFD and its very simple to set up and program...
 
adammichael said:
VFD's will only run 3 phase motors. You can run them with single phase power but it must be a 3 phase motor.
Click to expand...

Somebody should have told me this years ago when I bought a couple Optidrive VFD's and have been using them to run my 1 HP Single Phase motor on my lathe and my 2 HP Single Phase motor on my Mill!:eek:

Single phase in/Single phase out. As a matter of fact, the first VFD's built were specifically for single phase motors.
 
Interesting, those Optidrives. I think that may be the first time I've ever seen them mentioned here. Nice to know. Thanks.
 
89diesel said:
Somebody should have told me this years ago when I bought a couple Optidrive VFD's and have been using them to run my 1 HP Single Phase motor on my lathe and my 2 HP Single Phase motor on my Mill!:eek:

Single phase in/Single phase out. As a matter of fact, the first VFD's built were specifically for single phase motors.
Click to expand...
There was no mention of the Optidrive in any of the previous posts. The drives that were mentioned were for 3 phase motors.:eek:
 
Alden Sherrodd said:
................... It gives me speed adjustment of approx. 1500sfpm to 5600sfpm. I don't recall offhand the name on the pullies, but is is something like Vari-Cone. Several manufacturers make this type of speed control.
I previously posted photos and description of my setup.
Good Luck............
Alden
Click to expand...

Here's a set-up that I played with a while back. This 15 sec video is about 9 or 10 years old.

I'm using a vari-cone pulley on a lever...mounted between the grinder and the motor. This system is/was used on YardMan riding mowers for speed control. At least, that is what I understood at the time and I figured that if it works for a 10 hp mower, then it will work for a 2 hp grinder. I went the the local Yardman mower dealer and we searched through parts books until we found one that looked like it would work.

On the grinder, it worked great....but didn't have the speed range that I wanted. I can't remember what it was....but I wanted faster on the top and slower on the bottom...a little more than this would provide. Perhaps a different vari-cone pulley from a different mower would have done the trick. I used it for about 2 years...then picked up a DC motor and controller on Ebay....then switched to VFDs.

Here's the 15 sec video clip (mpg): http://beaumontmetalworks.com/1st-grinder/varispeed.mpg

-Rob
 
I looked up the post where I posted photos of the variable pulley setup. The name on the pullies is Roto-Cone, although I think most pulley/bearing manufacturers have a similar product. The rpm numbers I gave are as measured. The unit I have had been used on a combine used for grass seed harvest and used to slow down I believe a large fan.
Here is the link to the previous thread, with photos.
http://www.bladeforums.com/forums/showthread.php?t=606858&highlight=grinder
I hope this helps someone.
~Alden
 
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