KB AC drive

[PT Doc]

Hi guys. Have a 3hp Baldor and KB drive. This was running my KMG grinder with 6” drive wheel. I want to convert to direct drive. The motor is 1750 rpm so the resulting sfpm will be lower than what I want when direct driving. The Baldor if a gold high efficiency motor. Can I use the 2x option of the ac drive without creating a problem with the motor. Another option is to get a 10 or 11” drive wheel and not use the 2x feature. Thanks

 

[tkroenlein]

Yes. Just use the 2X feature. You will have a full range of speed control top to bottom. I rarely go above 70% with a 7" drive wheel.

 

[Hubert S.]

The KBAC drives also have a max speed trimpot that adjusts from 70-110%, so you can adjust that down if 2x is too fast. I have one set up with the 2x jumper and max speed trimpot pretty far down with a 7" wheel. Works well.

 

[DanF]

Not to derail the OP’s thread, but how do you know if a particular motor can be used with the KBAC 2x feature?

 

[Stacy E. Apelt - Bladesmith]

Almost any 3Ph motor suitable for a grinder will run at 2X on a VFD. We don't run them for hours on end at that speed.

 

[DanF]

thanks.

 

[Drew Riley]

Just a couple of notes for those who might be hesitant to "2x" their motors:

1) Motor bearings are typically rated for well past their operating RPM. For a double shielded 6205, for instance, the recommended limit is around 8,500 rpm. Even with a 3600 RPM motor, you're not going to hit that by doubling your speed, but DEFINITELY not with a 1750-1800 rpm motor. Depending on the type of bearing, it may even be rated in excess of 10k or more.

2) If your motor spins faster, your motor's fan spins faster, and it actually cools more efficiently. It's a little bit counterintuitive perhaps, but you actually risk over heating a slower turning motor more than a faster one.