KBAC27D question???

melsdad

melsdad

Joined
Apr 3, 2008
Messages
522
I did a search and didn't find what I was looking for.

Can this VFD run two motors? Not at the same time of course! I have a 2x72 grinder with this drive in use now.

I am looking to build a disc grinder. I have a second 2hp. 3 ph. motor I could use. It would be nice to save some cash and not have to buy a second VFD if possible.



Thanks
 
I am pretty sure the answer is yes: I do not have a KBAC, but it is no problem on most VFDs I have used.

Ideally, you would use identical motors, so that the protection settings are the same (and if you have a Sensorless Vector drive, it's even more important because the SV control looks at the power factor and adjusts the Voltage on the fly to maintain the motor rated power factor).

For a basic V/Hz (non-SV) drive, you could use the settings for the bigger motor and live without the full protection on the smaller motor.

I use plugs and a socket to change between machines and have a remote control box on a long lead that moves to the machine being operated.

It seems to be important that the output circuit is not broken under power. My feeling is that plugs and a socket give me more stop and think time than a changeover switch, so make it less likely I will break the circuit without first switching off and allowing the DC bus to discharge.

Others use changeover switches without problems.
 
I also use the socket with two plugs for my KMG and Disk grinders. With the KBAC-27D, it is important to wait until the two indicator lights go dark after powering down before disconnecting the motor. There is logic in the drive which can get confused if you disconnect the motor before the capacitors have discharged. -Doug
 
Now I decided to just use plugs to change power to which machine I want to use. One other question I can't seem to find the answer for is.

Do the r.p.m.'s on all the motors need to match? Can I run a 1725 r.p.m. then have a 3450 r.p.m. on another machine?
 
melsdad said:
Now I decided to just use plugs to change power to which machine I want to use. One other question I can't seem to find the answer for is.

Do the r.p.m.'s on all the motors need to match? Can I run a 1725 r.p.m. then have a 3450 r.p.m. on another machine?
Click to expand...

Do the r.p.m.'s on all the motors need to match?
No


Can I run a 1725 r.p.m. then have a 3450 r.p.m. on another machine?
Yes


You can mix HP too
 
Again, I can't answer specifically for the KBAC, but it's not been a problem on any of the other drives I've used.

If you are using higher-than-mains frequencies, you need to be aware of what you are running and set the speed accordingly.

120 Hz on a 4-pole motor is usually OK (assuming whatever it is driving can cope with the speed) at around 3600 PRM.

120 Hz on a 2-pole motor is around 7200 RPM and is much faster than the motor manufacturers design speed.

Most motors seem to be designed for 3600 RPM from the purely mechanical perspective. The same basic motor can then be fitted with 2-, 4- or more-pole stator windings to get different speed/power ratings.
 
Same voltage and phase. Don't exceed the HP rating of the drive with a motor.

I use a small drive with SO cord and twist lock connectors between the drive and motors.

4b9x.jpg
 
Thanks guys!! Appreciate the help!!

Now my wheels are really turning. A few years ago I got a Buffalo 15 bench top drill press. It had a 3/4 h.p 3ph motor on it. I switched it out for a single phase motor. I may put the 3ph motor back on and gain variable speed out of it. Running 4 machines or possibly more off of one drive seems to make the investment very worth while.
 
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I run both of my motors of of one VFD. Different set up than Ron, but way cheaper than a 2nd VFD
 
DougSeward said:
I also use the socket with two plugs for my KMG and Disk grinders. With the KBAC-27D, it is important to wait until the two indicator lights go dark after powering down before disconnecting the motor. There is logic in the drive which can get confused if you disconnect the motor before the capacitors have discharged. -Doug
Click to expand...
Mine doesn't have a power switch, so the lights stay on all the time
Should I install a switch, there is a place for one, or would unplugging the drive do the same thing? Don't mean to hyjack, but seems like it fits with he OP
 
Cody Hofsommer said:
Mine doesn't have a power switch, so the lights stay on all the time
Should I install a switch, there is a place for one, or would unplugging the drive do the same thing? Don't mean to hyjack, but seems like it fits with he OP
Click to expand...

I would suggest checking the drive literature for any cautionary bits, but other than that powering down your equipment is a pretty normal operation.
 
I plug the drive output into one of two motors currently. When I finish my drill press rebuild it will be three motors the one VFD will power individually. The switches on the output of the drive are forward and reverse. The second plug on the left of the drive is the same circuit, but it provides straight line power to another piece of equipment.

Like Salem mentioned, it gets old. I chose to do it this way for time, cost, and safety reasons. Though to be really safe I would ideally have a forward and reverse switch in between the motor and drive rather than two switches which can potentially short circuit your phases on the motor if you don't set them correctly before applying power.
 
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