Recommendation? Do I really need a VFD?

If you elect to stay with 120vac, buy a 2hp motor for the grinder. Set the VFD for 1.5hp and it will work just fine. Then if you ever do have 220vac you've already got the 2hp motor. Actually you don't have to set the CFD for 1.5hp, leave it at 2hp is just fine. The VFD doesn't have a clue what hp the motor is, only how much current is being pulled by motor. The only time that 2hp motor will pull full current is when you're REALLY leaning on it trying to bog motor down (pulling over 1.5hp of current), then the VFD will "protect" itself by shutting down on overcurrent. Do a reset and go back to grinding. The starting current surge is no load so won't be an issue.

Comments on that idea?
 
Ken H> said:
If you elect to stay with 120vac, buy a 2hp motor for the grinder. Set the VFD for 1.5hp and it will work just fine. Then if you ever do have 220vac you've already got the 2hp motor. Actually you don't have to set the CFD for 1.5hp, leave it at 2hp is just fine. The VFD doesn't have a clue what hp the motor is, only how much current is being pulled by motor. The only time that 2hp motor will pull full current is when you're REALLY leaning on it trying to bog motor down (pulling over 1.5hp of current), then the VFD will "protect" itself by shutting down on overcurrent. Do a reset and go back to grinding. The starting current surge is no load so won't be an issue.

Comments on that idea?
Click to expand...

I was actually just thinking about this idea. A KBMA-24D which is for 1HP motors came with my disc grinder. I am wanting to upgrade my regular grinder now too and use this VFD until I upgrade the VFD down the road. I called tech support for KB and they didn’t see a problem using a 2HP motor so I have it for when I upgrade to a larger capacity VFD. They just stated I wouldn’t get 2HP out of it.
 
Got the grinder (Black Fox One) and got the VFD on order (KBAC-27D). Now I need a 2hp 3ph motor.

And Automation Direct is out until - late August! Surplus Center - nada. McMaster-Carr - Success! at $700! :(

Any other ideas???

Thanks,
 
12345678910 said:
Crack the yellow pages for local motor sales and repair shops.



http://www.electricmotorwholesale.com/LEESON-119972/
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Ken H> said:
Automation Direct is out of stock on the 3600 rpm motor at $165 shipped, but they do have the 1800 rpm motor at $220 shipped in stock:
https://www.automationdirect.com/ad...eneral_purpose/general_purpose/mtrp-002-3bd18
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The 3600 version is the one I was looking for, or it's equivalent, both in tech specs and price. I really don't want to spend +$200 to solve a two month problem. :(
 
Albin said:
The 3600 version is the one I was looking for, or it's equivalent, both in tech specs and price. I really don't want to spend +$200 to solve a two month problem. :(
Click to expand...

Use the jumper wire setting for the speed double feature.

Lots of folks prefer the 1700 rpm motor - you can read lots of posts two pole vs four pole, more wire in the windings, running cooler and so on.
 
12345678910 said:
If you go three HP, you need to go to the more expensive vfd, the vfd needs 220 input. That's all stuff you said you wanted to avoid.

Where are you ?
and are you really an engineer.?
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Where did I say I wanted to avoid all that? I've always planned on 2hp 3ph at 230 VAC with a VFD.

2hp: 12 ga wire, 20 amp 2 pole CB both of which I've already got. KBAC-27D at $357
3hp: 10 ga wire and 30 amp 2 pole CB, which I don't. Plus I'd have to pull the 10 ga wire, yuck. The 3hp motor is a $50 hit. I'm debating whether it's worth it for the two months. The KBAC-29 is $360, a $3 wash.
 
Albin, I think the Count got you mixed up with the OP who was wanting to stay with 120vac input.

You might be surprised the 12 ga wire and 20 amp breaker working for the 3hp motor. Note the motor specs that give 7.4 FLA with 230 vac input. While the FLA starting amps is going to be more, the no load starting amps won't be all that bad.

The deciding factor is how far from breaker box will the VFD be located to be sure the voltage drop won't be excessive for 12 ga wire. As long as you're less than 50 ft distance VD won't be an issue.
 
Albin said:
Where did I say I wanted to avoid all that? I've always planned on 2hp 3ph at 230 VAC with a VFD.

2hp: 12 ga wire, 20 amp 2 pole CB both of which I've already got. KBAC-27D at $357
3hp: 10 ga wire and 30 amp 2 pole CB, which I don't. Plus I'd have to pull the 10 ga wire, yuck. The 3hp motor is a $50 hit. I'm debating whether it's worth it for the two months. The KBAC-29 is $360, a $3 wash.
Click to expand...


I was debating getting a 2hp 220v and went with a 1.5hp 120v. it's more than enough power, I just finished three 1/4" thick blades and didn't have any issues, for smaller blades I don't even run at max speed or I'll eat through the steel too quickly. I think 2hp would be nice if you are upgrading your electrical anyway but if you aren't I don't think you'll be disappointed with a 1.5 hp 120v VFD.
 
Ken H> said:
Albin, I think the Count got you mixed up with the OP who was wanting to stay with 120vac input.

You might be surprised the 12 ga wire and 20 amp breaker working for the 3hp motor. Note the motor specs that give 7.4 FLA with 230 vac input. While the FLA starting amps is going to be more, the no load starting amps won't be all that bad.

The deciding factor is how far from breaker box will the VFD be located to be sure the voltage drop won't be excessive for 12 ga wire. As long as you're less than 50 ft distance VD won't be an issue.
Click to expand...
I have a 20 amp circuit (12 gauge wire) run to the box that my 120V VFD is plugged in to. A run of perhaps 20-25 feet. Occasionally I will have real problems running the VFD at 80-100% (it will not settle down, try to run, shut down, try to run again, shut down, etc .... exactly what Ken is talking about). If I baby it and sneak the speed up, I can mostly get it to settle ..... but you perhaps can use this experience as a data point.......
 
Ken H> said:
Albin, I think the Count got you mixed up with the OP who was wanting to stay with 120vac input.

You might be surprised the 12 ga wire and 20 amp breaker working for the 3hp motor. Note the motor specs that give 7.4 FLA with 230 vac input. While the FLA starting amps is going to be more, the no load starting amps won't be all that bad.

The deciding factor is how far from breaker box will the VFD be located to be sure the voltage drop won't be excessive for 12 ga wire. As long as you're less than 50 ft distance VD won't be an issue.
Click to expand...

3hp = 10 ga wire; can't do much about that; I refuse to violate the NEC on something as basic as this.

The deciding factor for 3 hp is the VFD: KBAC-27d is good 2 hp. KBAC-29 is good to 3 hp (also good for 2 hp). So 3 hp = 10 ga + KBAC-29.

The distance I have to run wire is about ~75 or so. 100' of 10/2 w/gnd is about $100, so minimum of $150 to go to 3 hp and save 2 months.

Decisions, decisions.
 
Ken H> said:
Albin, I think the Count got you mixed up with the OP who was wanting to stay with 120vac input.

You might be surprised the 12 ga wire and 20 amp breaker working for the 3hp motor. Note the motor specs that give 7.4 FLA with 230 vac input. While the FLA starting amps is going to be more, the no load starting amps won't be all that bad.

The deciding factor is how far from breaker box will the VFD be located to be sure the voltage drop won't be excessive for 12 ga wire. As long as you're less than 50 ft distance VD won't be an issue.
Click to expand...


Yes, start your own thread ffs.
 
Albin said:
3hp = 10 ga wire; can't do much about that; I refuse to violate the NEC on something as basic as this.

The deciding factor for 3 hp is the VFD: KBAC-27d is good 2 hp. KBAC-29 is good to 3 hp (also good for 2 hp). So 3 hp = 10 ga + KBAC-29.

The distance I have to run wire is about ~75 or so. 100' of 10/2 w/gnd is about $100, so minimum of $150 to go to 3 hp and save 2 months.

Decisions, decisions.
Click to expand...


Why are you stuck on 3 HP?

Unless you're grinding off heavy forge scale from huge bowies and billets, 1.5 or 2 hp will do you.

Start with 2 hp, in a kgac27D, plugged into a normal 120vac 15 amp plug.
It will work in any plug.
It will probably do all you need to.
Get some experience with it before you go 3 hp.
 
12345678910 said:
Why are you stuck on 3 HP?

Unless you're grinding off heavy forge scale from huge bowies and billets, 1.5 or 2 hp will do you.

Start with 2 hp, in a kgac27D, plugged into a normal 120vac 15 amp plug.
It will work in any plug.
It will probably do all you need to.
Get some experience with it before you go 3 hp.
Click to expand...

No offense, but it sounds like you have a reading comprehension problem.

I'm not "stuck on 3hp". 2hp 3ph motors aren't all that available right now. 1 or 1 1/2 aren't an option. I'm not spending all this money to just go half way. Buying a 2hp, then choking it on 120 VAC makes no sense - at all - unless someone simply doesn't have 220 vac available in their shop. I've got power to burn. Plus "buying a 2hp" is the problem; not cord size or power or whatever.

As far as starting a new thread, this one seemed like a good option since the OP got his question answered and we obviously had a bunch of grinder experts on hand already. (I consider anyone who can spell VFD a grinder expert.)

I'm just looking for a 2hp 3ph grinder motor for a decent price; it normally shouldn't be hard, but now that I have a grinder, they all disappear. :(
 
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