Need help with Grizzly lathe motor

terry sims said:
As you may have suspected from reply #11, my problems have been solved by someone with a lot of influence at Grizzly. The motor is now on it’s way to PA for a make over at Grizzly’s in house motor repair shop. It’s nice to know that they can do this if necessary. This is not going to cost me any thing except the one way shipping to PA. Thank you Shiraz Balolia may all your groups be small ones.
Flatlander& Jay- If I had to buy a new motor your VFD suggestion is the way to go. I would love to slow that machine down when threading up to the shoulder, besides if Butch recommends it, it must OK.
Dusty- Called around to some motor repair shops in LR with no luck. Most will not work on import motors any more and those that will charge half the cost of a new import to rework the starter windings. Ben- I think brickeyee is correct about the starter contacts failing as the starter capacitor was toast. Thank to all that replied to this post.
Terry Sims :)
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In my line of work, I see a considerable number of VFD failures, usually from a phase module capacitor or charging circuit. They make a mess when them come apart as well.

With the 3ph option, you lose the starter winding cap, but then you add lots more of them in the VFD.

Although infinite speed control on a lathe is a wonderful thing (I have one at work). It is also more stuff to go wrong, and when it does, can get expensive.

Some times simpler is better.

I think you've made the right choice.
 
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This may be a stupid question but I have never seen it asked or answered anywhere. How does the VFD work with a two speed motor?

Dave
 
Flatlander yes your VFD has a max rating of 3hp and will work but you jeopardize the longivity of both the motor and VFD. When you double the hp rating of your VFD the motor startup is silky smooth and the motor runs cooler which=longivity! You only have to double size when feeding The VFD single phase.
 
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VFDs have changed over the last few years...

Older VFDs were over rated and required to have a 30% higher rating than the desired duty cycle. Today VFDs are rated at 100% of their rated duty cycle. Todays VFDs that are rated at 3hp will service a 3 hp motor.

That said I still recomend a 30% over rated VFD for the application.

My G9730 Grizzly lathe came with a 3hp single phase motor. I switched it out to a three phase motor. I learned the hard way. The first motor I bought was a NEMA three phrase 3 hp motor with a 1.25 shaft diameter. It would have required a lot of modification with the sheive/pullys to keep it geared correctly. After some research I found out that "metric three phase motors" were available. i found one with the exact footprint of my Grizzly three hp motor. It also had the same shaft size as my original grizzly 3 hp motor. Basically it only required a motor switch. The only problem was it was a 5.5 hp motor not 3 hp. Actually it has not been a problem. My lathe just has 5.5 hp now and not 3 hp as before.

I am using a Westinghouse TECO VFD. They can be bought from any HVAC supplier, Grangers, electric motor shop and on line with a company call Dealers direct. It is completely programable and works exactly like advertised.

Rustystud
 
Two speed motor

Dave:

VFDs produce true 3 phase current. VFD stands for Varriable Frequency Drive, this means that the VFD can be adjusted to vary the cycle rating of the current it produces. 90-99 % of the time one would run the VFD at 60 cycles as the norm. With a two speed motor you would not want to vary the frequency as the two speed motor may not have enought torque to drive the motor during start-up. Again that said I know folks who have varried the frequency on the high end leg of the duty cycle without any problems.

There are complete forums on VFDs & Phase converters. on the Home Shop Machinist web sites.

Rustystud
 
Rustystud said:
Older VFDs were over rated and required to have a 30% higher rating than the desired duty cycle. Today VFDs are rated at 100% of their rated duty cycle. Todays VFDs that are rated at 3hp will service a 3 hp motor.

That said I still recomend a 30% over rated VFD for the application.





Rustystud
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VFDs are good for 100% of their rated duty cycle if feed with 3-phrase power!
 
Dave Tooley said:
This may be a stupid question but I have never seen it asked or answered anywhere. How does the VFD work with a two speed motor?

Dave
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You can wire it to either speed, normally you use the high speed windings, and don't bother with the low speed, since you can just lower your speed with the drive.

The only good reason I could think of to use the lower speed windings, is if that speed at 60hz is absolutely as fast as you'll ever need.

Drives do have an efficiency curve, and at lower speed/high torque efficiency suffers.
 
Thanks Guys

I've got 3 phase power to it now. I have a rotary phase converter running everything in the shop. The only problem is it's a 3 HP phase converter and my 14" Clausing is 4.5HP on high speed. It's 3 HP on low speed so that's what I've using and everything is working just fine. There are times when high speeds would be nice to have but most work is done under 1000 RPM's anyway so I don't know if I would be gaining anything by using A VFD wired to the high speed side. There are large gaps in the speeds being limited to using the low speed side of the motor though.

Dave
 
I can't picture any gunsmithing job that would need more than 2 hp motor on a lathe, unless you do production runs of 20 mm cannon barrels. Put a clamp-on ammeter on one wire from the breaker that feeds the lathe, and I'll bet that any threading or chambering job will be reading less than 7 amps for a 240 v single phase motor. That's the equivalent of 3/4 hp, actual power used. A 2 hp VFD will be fine, using a 240 v 20 amp single phase circuit, and running a 3 phase motor from it is nice and smooth. Just keep the speed above 2/3 of its rated speed, for cooling the motor, like 40 hz on the VFD readout. PS: What do I have on my old Atlas? 1/2 hp, and it does 1/16" cuts at 150 rpm just fine. I'll send you the prize winning 8' long curl from turning down my 458 double rifle barrel, if you want.
 
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Dave Tooley said:
Thanks Guys

I've got 3 phase power to it now. I have a rotary phase converter running everything in the shop. The only problem is it's a 3 HP phase converter and my 14" Clausing is 4.5HP on high speed. It's 3 HP on low speed so that's what I've using and everything is working just fine. There are times when high speeds would be nice to have but most work is done under 1000 RPM's anyway so I don't know if I would be gaining anything by using A VFD wired to the high speed side. There are large gaps in the speeds being limited to using the low speed side of the motor though.

Dave
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Dave, I like to run the Clausing variable speed with the lathe in lower gear and motor revved up a little more.

I find if I run the lathe in high gear, and turn the VFD slow, it's hard to get fine speed control when I want to go very slow. Also, I get droop, that is, the the lathe slows down because torque is low in high gear.

So, I'd suggest wiring the VFD high and running the lathe in a lower gear for better speed control.

Ben
 
Terry-
Call my boys at Lynn's Electric Motor 501-337-0018. talk to Lynn or Ken and tell em I told you to call. I spend a little bit of money over there so maybe they'll help you out. if not get it to me and I'll take care of it.
 
update on the update

Good news and bad news. THE GOOD: I received the motor back from Grizzly today. Installed it and took it for a spin. Everything seems OK. Because of the age of the lathe, Grizzly was under no obligation the fix the motor but they did at no cost to me. Thanks again! THE BAD: I have no more excuses.
Terry
 
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