couple questions about 1 VFD to multiple motors

NickWheeler

NickWheeler

Joined
Dec 3, 1999
Messages
9,437
Hey guys- :)



The DC motor+controller set up that runs my 9" disc has been trying really hard to crap out on me this year.

Thanks to some posts by Nathan, Ben, Salem, Erin, and Sam... I decided to try running multiple motors off one of my VFDs. I went with the KBAC-27D that's on my 2hp KMG.

I got a great price on a brand new 2hp Baldor, and also had a "new" Leeson 1hp (it was taken off a new industrial fan by a guy that replaced it with a single phase motor, then it sat in his shop for a few years).

So I got it all wired up with toggle switches...

Questions:

#1.)- Since the motors draw the amps in... It won't hurt the 1hp motor to be controlled by the 2hp rated VFD will it? I can't see how it would... but since there's a little hp designation lug inside the VFD, I thought maybe I'm overlooking something.

#2.) The Baldor seems to "start kind of hard." :foot: I don't know the proper lingo for this, so it's hard for me to even ask the right question here. :o But when I switch power over to the Baldor it almost seems like it has a big surge of torque right as it starts turning. But then it spins super smooth and quiet---as you'd expect a Baldor to do. Any ideas what's going on there? :confused:


Thanks guys! :)
 
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But when I switch power over to the Baldor it almost seems like it has a big surge of torque right as it starts turning.
Click to expand...

Does that mean that you've been switching running power from one motor to the other? The VFD has ramp-up and down parameters that control stop and start of the motor. It's good to switch the VFD from "run" to "stop", then switch the output lines to the other motor, then hit "run" again. My apologies if this is not the problem and seems to obvious...

As for the jumper, I don't know about the KBAC. I run a Teco FM50 203, which just handles motors up to 3hp. I don't know why the KBAC would have a jumper- it would seem that as long as the max horsepower is not exceeded, it's simply a variable frequency 3 phase output of so many amps. Perhaps the KBAC is more efficient when optimized to a more specific hp range?
 
Sounds like it could be the ramp up is really slow. That makes it slower to get going but easier on the motor. There is a constant torque jumper that could need to be changed. I would call kb and speak with the tech dept. Charles was very helpful with setting up my baldor 3hp grinder motor. The manual is very thorough but 2 motors adds complexity to the solution. Good luck. Keep us posted.
 
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NickWheeler said:
Thanks to some posts by Nathan, Ben, Salem, Erin, and Sam... I decided to try running multiple motors off one of my VFDs. I went with the KBAC-27D that's on my 2hp KMG.

I got a great price on a brand new 2hp Baldor, and also had a "new" Leeson 1hp (it was taken off a new industrial fan by a guy that replaced it with a single phase motor, then it sat in his shop for a few years).

So I got it all wired up with toggle switches...

Questions:

#1.)- Since the motors draw the amps in... It won't hurt the 1hp motor to be controlled by the 2hp rated VFD will it? I can't see how it would... but since there's a little hp designation lug inside the VFD, I thought maybe I'm overlooking something.

#2.) The Baldor seems to "start kind of hard." :foot: I don't know the proper lingo for this, so it's hard for me to even ask the right question here. :o But when I switch power over to the Baldor it almost seems like it has a big surge of torque right as it starts turning. But then it spins super smooth and quiet---as you'd expect a Baldor to do. Any ideas what's going on there? :confused:


Thanks guys! :)
Click to expand...

If I'm the Sam in that list then, glad I could help.

I had the same question as your #1.
It seems reasonable to assume what you are and it's not covered in the manual- but that's some pretty expensive smoke so I also asked the KB electronics people the same question.

The HP designation jumpers set the internal protection limits for the controller.

So a 1HP motor cannot exceed the limits of the 2HP controller, but if you do use a 1HP motor on a 2 HP controller, you have less protection for the motor.

In our application letting a disc spin up has practically zero startup load compared to some industrial applications like starting up a loaded conveyor belt (or whatever)
-so no probames expected with that.



Re# 2

As Salem mentioned, I turn off before I switch over (I use plugs instead of switches so It's kind of inherently forced.)

Are you using the settings Rob suggests on his web page?
http://www.beaumontmetalworks.com/VS-setup.html
"Tuning adjustments for optimum performance"

He adjusts
Acceleration, boost and comp
to basically use a softer lower torque start.


It's odd that the motors would act differently when the controller is the same.

Are you testing this with a load- like the disc installed on the motor ?
I do remember when I first hooked up the controller to a bare motor I got all sorts of jumpiness that disappeared with a drive wheel on (flywheel effect)



(I don't mean to pester you, but I still haven't been able to receive your email on the RP. Perhaps the attachments are too large?
Maybe cut and paste text to the email or just one photo per email or something may work out better.)
 
Thanks guys-

Salem- I read enough "don't set up your VFD with multiple motors, you'll blow up your vfd" posts on the interwebz (mostly on practical machinist), that it has me paranoid enough to completely power down everything before switching from one motor to the other. :o so that's not an issue.

There might not be anything wrong at all, it just seems that the Baldor starts up quite a bit differently than the two Leeson motors. I'll try to get a video of it since that would explain it a lot better than I did, LOL.

Thanks again fellas :)
 
Sam- Must have been typing at the same time. Yes, you are the Sam I was referring to ;) :)

I set up my VFD to Rob's suggestions back when I got it in '07 and haven't changed anything in the VFD at all since. Well, other than recently adding a fwd/rev switch to the board.

I tested the Baldor with a Frink 9" aluminum disc, and had it clamped down to the bench also.

As per the email, IDK what the heck is going on. :confused: I'll have to try again.
 
NickWheeler said:
Sam- Must have been typing at the same time. Yes, you are the Sam I was referring to ;) :)

I set up my VFD to Rob's suggestions back when I got it in '07 and haven't changed anything in the VFD at all since. Well, other than recently adding a fwd/rev switch to the board.

I tested the Baldor with a Frink 9" aluminum disc, and had it clamped down to the bench also.

As per the email, IDK what the heck is going on. :confused: I'll have to try again.
Click to expand...

With those settings and the disc on, I'm stumped too.


Thanks for the info resend.
I'll reply to you when I get it so you know.
 
Well.... watching this video makes it look/sound like there's not really anything weird going on... but it does seem a little weird in person. :confused:

[video=youtube;Se7TtNZ2ru8]http://www.youtube.com/watch?v=Se7TtNZ2ru8&feature=youtu.be[/video]
 
Sadly I have no useful info to add. I run 2X 2HP motors of a 2HP rated VFD.

But that new avatar is priceless Nick. Thanks for the good laugh. :D:D:D
 
Nick, are you talking about a rough initial startup or the "pulsing" feel of the motor at lower RPM?

I run same VFD and switch it between 2 identical 2HP baldor industrial motors. I notice the exact same "pulsing" at low rpm that I think I saw/heard in your video. When I adjust the RPM, it smooths out nice and runs great. I started with the settings from Beaumont's site on my setup but then thought it was odd how it was working and spent at least a day tweaking every setting and pouring over the KBAC manual. I think I have mine set as best I can, but it seems my motors do exactly what yours is, and I have 2. So, it's not a motor fault since they both do it.
 
My 3hp Baldor motor on the big grinder pulses a bit at very low RPMs, but it seems to me that Nick is describing (and I can kind of see it in the video) a rough startup and shutoff.

You might call Baldor, or a larger Baldor dealer and ask to speak with the service department. Explain that while you do not own a motor on warranty, you would greatly appreciate it if you could trouble them with a couple of quick questions. You know, nice and polite- I've gotten a lot of free, good advice from service departments and dealerships this way.

ETA: FWIW my Leeson 2hp runs more smoothly at low RPMs than my Baldor 3hp, from the same VFD. I do have another 3hp and two 2 hp Baldor industrial motors sitting around, I'm curious now to hook them to the VFD and test them for smooth starting...
 
I had the twitching/vibrating/hopping at a mid rpm range prior to connecting to the kmg. This is what caused me to call kb and they helped out in the end with torque jumpers. KB really has a good understanding of their vfd and they will sort you out or verify that you have it spec out ideally.
 
Thanks for the replies fellas. I think what I wanted to come through in the video didn't, and sounds like something that isn't there...somehow did. LOL They all run very smooth throughout the rpm range. Well, the 1hp Leeson does act a little jumpy if I turn the rpms down really fast, but that's the only time.

I think it's more a self-worry issue than anything. But the advice to get in touch with Baldor and KB electronics is certainly a good idea.

An interesting note here--- I got the 1hp Leeson crazy cheap, somewhere around $50....BEFORE I looked into how motor rpm (# of poles really) would factor into the equation. The little Leeson is 3600rpm, so I ASSumed, after reading about poles and rpms, that I was gonna be screwed with it... that it was going to act like a little pissant of a motor running off the VFD. But I put a 9" disc on it last night, with 120X rhyno paper... and it still has way more ballz than my 1.5hp DC motor+controller did.

I think when I get a disc set up on the 2hp, 1800rpm motor, it's gonna want to rip my arms off. :eek: ;) :)
 
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