Please help me choose a motor & VFD for a vintage Rivett lathe

[cazclocker]

I'm buying a vintage Rivett 715 plain-turning lathe (no screwcutting capability) from a friend in the next couple of months. I have a fair idea what I'll do for a bench, but I obviously need to choose a motor. Right now, I'm in the process of narrowing down my choices of an AC motor from Surplus Center.

I will also need to choose a VFD - I watched the videos by TubalCain with great interest on how he installed a VFD on his drill press. Do I need to wait until I pick a motor to choose a VFD? Or can I start choosing now? My electrical source will be a 220VAC dryer outlet in my shop.

Thanks in advance...
...Doug

 

[JimDawson]

Before you choose a VFD, you will need the motor horsepower. You will be choosing a 3 Phase, 230/460 volt motor. And connecting it for 230V. That's all there is to it.

 

[CluelessNewB]

Make sure you read the fine print on the Surplus Center motors. Make sure it is "Continuous Duty". When selecting a VFD typically the horsepower rating will get you the right one but you should also check the current rating. The VFD should be rated for at minimum the rated amperage of the motor. For example on a 230/460 volt motor you may see amperage 2.8/1.4, the higher number (2.8) is the current at 230 volts and is what you would use to select a VFD. You will want a "sensor-less vector" type of VFD for a lathe (so skip the Teco FM50). I have used Teco N3 and Teco 7300 both work well. If I was buying today I would look at one of the Teco JNEV VFD's. Hitachi has a good reputation also. I have one eBay cheapo but I would recommend spending a few extra bucks.

 

[cazclocker]

Before you choose a VFD, you will need the motor horsepower. You will be choosing a 3 Phase, 230/460 volt motor. And connecting it for 230V. That's all there is to it.

Thanks, Jim! With the parameters you mentioned, my choices just got cheaper - that's a good thing. I need at least 1 horsepower. So Surplus Center offers a 1 HP motor and I'm also looking at a 1.5 HP motor.

So how do I now choose a VFD? I'd like to stick with Surplus Center - no particular loyalty here, I've had good experiences with them in the past and I'd rather order the motor and VFD from one place unless there's a compelling reason not to. Their line of VFD's can be seen HERE.

Thanks,
...Doug

 

[cazclocker]

Make sure you read the fine print on the Surplus Center motors. Make sure it is "Continuous Duty". When selecting a VFD typically the horsepower rating will get you the right one but you should also check the current rating. The VFD should be rated for at minimum the rated amperage of the motor. For example on a 230/460 volt motor you may see amperage 2.8/1.4, the higher number (2.8) is the current at 230 volts and is what you would use to select a VFD. You will want a "sensor-less vector" type of VFD for a lathe (so skip the Teco FM50). I have used Teco N3 and Teco 7300 both work well. If I was buying today I would look at one of the Teco JNEV VFD's. Hitachi has a good reputation also. I have one eBay cheapo but I would recommend spending a few extra bucks.

Clueless, sorry I didn't see your post! On the 1.5 HP motor from Surplus Center I don't see the word "continuous" anywhere, but I do see a pair of amp ratings (4/2 amps). So I see that this motor will run at 4 amps at 230 volts.

If it was you, where would you shop for motors?

 

[Ulma Doctor]

just a fyi ...
you can over-rate the VFD, that is to say, if you are running a 1 hp motor, it doesn't hurt if the VFD is rated for 2 hp.
if the price is right and you have the ability i would go a little larger if possible.

but that's just my 2 cents, but, i get paid to repair other's mistakes.

as far as where to get a motor many surplus companies have them pretty cheap
baldor is a good name
sew eurodrive also is top notch
the dayton motors can be used with sucess
but any 3 phase air compressor duty motor around 1740 rpm will work fine but you'll have to watch out for using the motor at low speeds for too long a period of time.
an inverter duty would be optimum but they can be expensive
i hope the info helps out

 

[rdean]

I agree with Ulma Doctor on sizing up. I have used Woods, Allen Bradley, Lenze, and Siemens VFDs over the years and I always up one size when installing. All drive manufactures I am familiar with have cheapened their drives to save money and be competitive. Some even tell you they are not for continuous full load amps.
Go one size larger and it will be well worth the price.

Ray

 

[JimDawson]

Doug, I just took a look at the motor you linked to. I think it has sleeve bearings, not what you want.

In the same price range, they also have some 1.5 HP Chinese motors, that are ball bearing, continuous duty, and are 230V only. The down side is that (1) they are Chinese, and (2) they have a 22mm shaft rather than a 7/8. It is a standard metric size, so you can get pulleys for it, or use a 0.005 shim wrapped around the shaft to use a 7/8 pulley, and modify the (6mm?) key to fit.

I agree with Ulma Doctor that upsizing the VFD can't hurt.)

 

[CluelessNewB]

Also do you really want a motor that runs that fast? Typically on a lathe you would want an approximately 1800 rpm motor not a 3600 rpm motor. Note the 1hp motor link you shared has a very weird oddball shaft and a duty of only 2 minutes (not continuous).

The Surplus center VFD's are all TECO FM50's (not ideal for a lathe) except 11-3424 which is a Teco JNEV 101-H1 which would work well but it is 115V input (might even be preferable). Just remember when you go with a 115V input VFD the currrent draw on the 115V line will be high so you probably can't share that circuit with much else. As others have said oversizing a VFD isn't a bad idea.

If I was buying a new motor I would look for a TEFC (totally enclosed fan cooled). For a small lathe like that 3/4 or 1hp should be plenty.


Surplus Center has some cool stuff but make sure you check shipping prices, they can be a deal breaker.

I have bought VFD's but not motors from http://dealerselectric.com/ they also sell VFD/Motor combined packages that look attractive.

 

[cazclocker]

Yes, I am positive that I need a motor rated at 3600 RPM or thereabouts. The lathe is a vintage precision bench lathe that was originally designed to run at a maximum of 3500 RPM. The lathe spindle runs a pair of size-matched V-belts which pass through a hole in the bench straight down under a headstock cover. I just found out that my friend who is selling the lathe to me will supply the SAME SIZE pulleys for mounting onto the motor shaft, so the drive ratio will be 1:1.

So far I now know that I want a 230/460 VAC motor, 1hp - 1.5hp, 3600 RPM (+/- a few RPM's) and (for reasons I don't understand) I don't want sleeve bearings.

Why are sleeve bearings not desireable?

I have yet to pick a VFD - thanks for suggesting dealerselectric.com.

...Doug