Appropriate size motor GIB/EERF

B

Brian.Evans

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Aug 20, 2011
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Owners especially chime in. What size motors are you all running on your single speed or VFD controlled motors.

Here are my options
The VFD is $250 shipped

Single phase 2 hp 1750 rpm - $125
Would be used for a single speed grinder. Arguably the cheapest route, but I'd really like variable speeds.

3ph 1.5 hp 3600 rpm - $78
Would be used with the VFD

3ph 2 hp 3600 rpm - $175
Would be used with the VFD. Is the extra .5 hp worth $100??

I'm really leaning towards the 1.5 hp with the VFD. The VFD is a NEMA 12 rated for 3 hp, so would be upwards compatible if I wanted to upgrade later.

I guess what I want to know, is 1.5 hp "enough"? I'm not a full time maker by any stretch, I just want a nicer grinder.
 
IMHO YMMV etc etc, 1.5hp is sufficient, especially with vfd, but I wouldn't go lower. My *impression* is that 90% of the vfd grinders used by fulltime makers are probably no more than 1.5hp, since a kbac 27d will only produce 1.5hp with 110-120V input.

I've recently upgraded my primary grinder to 3hp, running a kbac 29, from 220V 3ph input, and I'm loving it, but I only notice the difference with the flat platen. I never bogged down the previous 1.5hp motor with a contact wheel, since they have traction, but could, on the platen.

Hope that's helpful.
 
Just to be clear, a 2hp motor will only output 1.5hp with 110v input, with the kbac 27d, regardless of the motor rating, for anything higher than 1.5hp you'll need 220v. That may make the choice obvious.
 
I have a 1.5hp 3ph motor running off 110v. I do slow it down when running at full speed on the flat platen.
I'd prefer a 220v 2hp if I had dedicated power.

Also, when running a motor with a VFD, it's recommended to run a 1725 RPM motor as it will operate well at high speeds, and get better performance at lower speeds than a 3450 motor.

My KBAC27D VFD has a 2x speed setting that allows my 1725 motor to be run at 3450....I have a GIB running on mine.



I know you said you have 220 in your shop, so I'd go 220 2hp.
 
javand said:
I've recently upgraded my primary grinder to 3hp, running a kbac 29, from 220V 3ph input, and I'm loving it, but I only notice the difference with the flat platen. I never bogged down the previous 1.5hp motor with a contact wheel, since they have traction, but could, on the platen.

Hope that's helpful.
Click to expand...

How nice to see someone running the 29 single phase input vfd. I have this on order and will be controlling a Baldor 3hp 1750.

Any issues connecting yours to your motor? What rpm is your motor? What size pulley on the motor and grinder? What size drive wheel?

Sorry for all the questions, I'm just very excited.
 
Let me be clear, my 29 is a weird model; 9528B, which accepts both single phase and 3 phase input. It claims only 2hp output with 220v single phase input. I'm not sure what the real internal differences between this model and the other 29's are that can power 3hp with 220v single phase are, but I bought this vfd a while back before there was much clarity about the 29s, and the site I got it from had it listed as being capable of powering 3hp from 220v single. I only realized months later when I got around to installing it, that there was a discrepency.

Since I've got a digitally controlled 10hp rotary phase converter, I'm just supplying 3ph power via it. Afaik, there isn't any reason not to.


As to the config, I'm running it with a 4" drive wheel, it's a 1750 rpm motor, and I'm using the 2x multiplier on the vfd. No pullies, since this is a gib build. Haven't had any probs. I'm sure I could run a larger drive wheel if I wanted, but I'm not a stock removal guy, so I've never needed half the speed.
 
Well, I have found two motors locally:
Both 1800 rpm and 2hp and 3ph.

One is brand new and is $195

One is a 1986 Baldor used at $125.

What do you guys think?
 
medicevans said:
Well, I have found two motors locally:
Both 1800 rpm and 2hp and 3ph.

One is brand new and is $195

One is a 1986 Baldor used at $125.

What do you guys think?
Click to expand...

I replied to this same question in the other post but will post again.

To give you a frame of reference, I bought a 3 hp 3 phase new Baldor 1750 rpm for 250. Likely could have gotten it cheaper. What brand is the other motor? I'd pass on the 26 year old Baldor.
 
Per Local Baldor office, choose a "super e" motor when using with vfd. These motors will have an e in the motor number:EM####T.
 
I have a single phase 2hp motor running on 220 with belt/pullies. It runs 3600 rpm and I NEVER run it full speed. Mostly because I am afraid of a belt snapping on me at that speed. It is a 4 speed and I find that the lowest three speeds more than enough suit my needs.

I have never even almost bogged it down and have had no issues at all with the belt slipping. The running motor does vibrate the table it is bolted to just a bit but not that bad. I would gladly build it again.

Jason
 
jawilder said:
I have a single phase 2hp motor running on 220 with belt/pullies.

It runs 3600 rpm and I NEVER run it full speed.
Mostly because I am afraid of a belt snapping on me at that speed.

It is a 4 speed and I find that the lowest three speeds more than enough suit my needs.

I have never even almost bogged it down and have had no issues at all with the belt slipping. The running motor does vibrate the table it is bolted to just a bit but not that bad. I would gladly build it again.

Jason
Click to expand...

This brings up an excellent point.

The use of the phrase "step pulleys" on the KMG is pretty vague

In most cases, there is a 3 step pulley and a 1700 rpm motor

The pulley ratio is usually

234
432

so the effective rpm of the drive wheel is

50% of 1700
100% 1700
2x 1700 (which is equal to the 3400rpm that direct drive grinders like Bader, and others use.

so those steps are equivalent to full, half and quarter speed of a Bader with a 3400 rpm motor (assuming same size drive wheels)


the 4 steps with a 1700 rpm motor will be

2345
5432

40% of 1700
75%
133%
250% which is an extra 700 prm faster than the 3 steps

with 3600 rpm motor, those are all doubled again - I would be afraid of that too.
a smaller drive pulley could bring those speeds down so you have a greater variation at the low end.


SFPM is really a better and more comparable measurement but it takes some calculations.
3400 rpm direct drive on a 6" drive wheel is 5100 SFPM surface feet per minute = a pretty common max speed.
step pulleys and jack shafts take more math.
 
Last edited:
PT Doc said:
I replied to this same question in the other post but will post again.

To give you a frame of reference, I bought a 3 hp 3 phase new Baldor 1750 rpm for 250. Likely could have gotten it cheaper. What brand is the other motor? I'd pass on the 26 year old Baldor.
Click to expand...

The date code is a neat bit of info, but motors aren't like fruit.

I have motors that must be 60 years old or more and work well.
maybe they aren't as efficient, and they sure are much heavier, but overall I don't see any disadvantage to using an old motor.


Especially if you can buy NOS new old stock that has been on the shelf for years, it's essentially new at a great price.

Why not buy old motors ?
 
12345678910 said:
Why not buy old motors ?
Click to expand...
I tend to agree with you Sam, although I did just run in to what might end up becoming a problem for me down the road with a DC motor. While searching around for an optional foot mounting kit for it, I have discovered GE discontinued the model some time ago and they no longer have its parts in stock. So when it comes time for replacing brushes/springs/caps or bearings I might have some challenges. AC motors would not have as many of these issues though.
 
Phil Dwyer said:
I tend to agree with you Sam, although I did just run in to what might end up becoming a problem for me down the road with a DC motor. While searching around for an optional foot mounting kit for it, I have discovered GE discontinued the model some time ago and they no longer have its parts in stock. So when it comes time for replacing brushes/springs/caps or bearings I might have some challenges. AC motors would not have as many of these issues though.
Click to expand...

that's a good point Phil, but I suspect that at least bearings and brushes will be so generic that you won't have any troubles.
 
Brian,

What I don't see you listing is whether the motors are TEFC or "Drip Proof". Here's a guess... anything running in the 3600 RPM range is "drip proof" and not suited to be your grinder motor. It's not all about horses and RPMs. You need to pay attention to the enclosure too.
 
Thanks Greg. Actually, all the motors I've listed are TEFC. I've passed on some awesome deals on ODP motors because they were ODP. There are several several 3600 rpm TEFC motors out there.

That is a good point for future readers of this thread though. TEFC is the way to go, NOT ODP.


As far as the 26 yr old Baldor, it's used, not NOS, but the lady behind the counter said she has more faith in the old Baldor motors than the new ones. I tried for $100, but she wouldn't budge. Haha.

26 year old Baldor, or new no name brand?
 
You should take note of some of the other threads about motors posted recently. There are some good deals (even on Baldors) out there at HGR and HGRauctions.
 
There's another thread a little ways down the page started by David66 that pointed me to a good seller.

I believe he's in Chicago and has a 3hp 1740 rpm 3ph USA made Leeson for $235, and a 2hp for $209, delivered.

Three hp here I come?
 
Greg, help me out with a listing? I can find any larger motors on HGR auctions, but I'm on my phone so that may be why.
 
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