Estimating a VFD

[Olaf Vogel]

I managed to purchase a (new to me) old pattern lathe. Not much background on it, but seems to be from about 60-70's, used by and possibly made by Canadian Machinery Corp. max 32" dia, about 6' c-c, roughly 1500 lbs.

So I'm currently cleaning it up, repainting some spots and fixing a few small issues. But otherwise, its seems to run fine.

It currently has a 1 hp motor and a 3 speed transmission, with a stick shift, that looks like something off a tractor! I'd hoped to fit a larger (and newer) 3 hp version I have sitting around. At the same time, I'd like add a VFD to control the speed more accurately. So a couple of questions.

1 - any recommendations on what to look for in a VFD? Feature wise, it seems I want: (a) constant HP, (b) soft start, (c) easy speed control (a good ole fashion knob would be nice). I really don't want to use any PC interfaces, rather control everything from the box. The shop is way too dusty for a PC.

2 - any good sources? eBay has a ton.

3 - What size? If I go the "dumb" route and just get something higher rated like 5 hp, is that sufficient overhead? Or should I work through some calcs to figure this out, have found some sources.

Thanks for your help.

Olaf

[Dan Hintz]

1 - any recommendations on what to look for in a VFD? Feature wise, it seems I want: (a) constant HP, (b) soft start, (c) easy speed control (a good ole fashion knob would be nice). I really don't want to use any PC interfaces, rather control everything from the box. The shop is way too dusty for a PC.

2 - any good sources? eBay has a ton.

3 - What size? If I go the "dumb" route and just get something higher rated like 5 hp, is that sufficient overhead? Or should I work through some calcs to figure this out, have found some sources.
Google Hitachi VFD... they make some nice quality ones in the 3-5HP range for around the US$300 mark. There's a cheaper one people seem to like, but the website escapes me at the moment. One of the Hitachi's has a removable control panel so you can hie the controller itself and mount the control panel to the lathe.

[Mike Cruz]

I got my 2 hp FM-50 from Factorymation.com, talk to Jeremy...great guy. It works great. Mine was $145. I think the 3 hp unit was $250. Yes, you can control your lathe through the VFD, but I would get separate controlers because of two reasons. 1) you have to mount it close enough to be able to comfortably be able to access the buttons, and 2) VFD buttons are kinda small, and they are arrows that you have to push (I mean that to increase from 2 to 9, you have to push the up arrow 7 times), that kinda thing. Whereas if you have a knob to turn, it is much more user friendly. They have all those things. I got a box, a forward/reverse switch, and potentometer (knob to control lathe rpm speed) with room in the box to also mount the tach display that I bought for the lathe.

Also, what I learned about this whole process is that while my FM-50 is rated as 2 hp unit, what is really important is the motor amps, not really the HP. What I mean by that is that my unit is rated up to 7.5 amps. I replaced my 1 hp motor with a 2 hp motor. My 2 hp motor is only 5.4 amps. So really, if I had found a 3 hp motor that was 7.5 amps or less, I would have been fine. Likewise, I had to make sure that the 2 hp motor I got wasn't over 7.5 amps. Really, I don't know how many lathes require a 3 hp motor. I believe that even the new PM lathes are using 2 hp motors.

Also, just to make sure... You are talking about a VFD for a 3 ph motor, right? I am. Not sure if VFDs work on single phase or not.

If you have any other questions, I'd be happy to give it my best shot. But, again, Jeremy at Factorymation.com knows the real answers.

[Olaf Vogel]

Thanks for the feedback. I really would like to have a dial to change the speed, so not having push the buttons too much. Good point about the amps, vs hp. I'll call a few of the shops and see what they recommend. The Hitachi units seem popular and easily available.

The existing motor is single phase 110V, the new one is 3P, 220v. Maybe its overkill, but I've already got it.

thanks

[Richard Bell CA]

Olaf:

I installed one of these on a 20" disc sander and it works well. This site has a wide variety of drives.

http://dealerselectric.com/item.asp?PID=394&cID=28&scID=165

Richard

[Olaf Vogel]

After looking at a bunch, I do like th Hitachi VFD: decent controls including a speed adjust knob, readable instruction manual (in reasonable english). There's 2 versions recommended.

X200 - 037LFU
http://www.driveswarehouse.com/documentation/Hitachi/X200B.pdf
- 16 amp output to cover my 13 amp needs)
- variable torque - seems like a good idea to be able to get more torque at lower speeds/larger diameters - but not sure if VFD's work that way. Since there is a transmission, I'd but it in low gear anyway for a large piece.

I read somewhere that variable HP was more important for lathes than variable torque. Obviously starting a large piece will take torque, but then continuously cutting a large diameter may take HP (If I remember my automotive theory correctly)

- trip avoidance - I read that as a the VFD regulates the load so the circuit breakers don't trip. I.e. heavy load gets accelerated slower?
- second motor setting: I heard that at low rpms a motor could overhead because the internal "fan" doesn't move enough air. I guess a secondary fan could be bolted on to provide airflow. Again, seems like a good idea, but I don't know if I'd really need that.
- doesn't have a remote keypad - nice feature - don't really want to reach around a large spinning (esp. flying) object to shut down the lathe.
- $100 cheaper


SJ200 - 037LFU
http://www.driveswarehouse.com/documentation/Hitachi/SJ200B.pdf
- 17.5 amps, a little more overhead - not sure I really need that
- 2x regular starting torque. I'm guessing this doesn't come for free, so might require more amps in the circuit.
- remote keypad - just remove and add wires - I like that!

Plus a bunch features I don't understand, so likely won't figure out - kinda like my TV remote controls. :)
- analog set point

The only major improvement I see from this version is the remote keypad option.

Thanks for any feedback. Olaf

[Dennis Ford]

I have the X200 version and have installed the same on friends machines. It is a good unit, I am not sure the extra features of the "SJ" are worth the cost for use on a wood lathe. Variable torque does not mean that you get more torque at low speeds unfortunately it is the other way around. Actually the torque is fairly constant except at very low speeds. Either the "X" or "SJ" will have a lot of features that you won't use.

You may not need a remote keypad, my controls consist of: potentiometer (speed control), toggle switch (forward, reverse), start button and stop button. I also have and recommend an additional stop button. The instructions are good and show several ways to wire up controls.

Airflow through the motor is a concern at low speeds but so far has not required a separate fan.

[Olaf Vogel]

Dennis, thanks for this feedback - exactly what I was looking for. I was inclined to skip the extra features and go with the simpler version.
I think I'd be ok with the standard controls, I'll just mount the VFD near the tail stock and out of firing range. Thats just a bit more cabling.

Thanks!

[Andrew Frandsen]

I recently did my General 260 with a VFD (Delta brand). I love it and it is a definite move up from the Reeves drive. A friend who is an industrial electrician did the wiring and programming for me and was very helpful. Mine is mounted on the wall behind the headstock. Two recommendations from the electrician were to not operate it below 20 Hz under load for very long as this would cause the motor to heat up and to protect it from dust. The internal fan draws dust through it as it cools itself. I have toyed with the idea of building an enclosure for it but I'm not sure how feasible that would be. The best solution, I am now thinking, is to move it some distance from the lathe and use a remote control pad. One further note is that my unit stays running while power is supplied to it so I added a switch in front of it on the circuit. Stop and start is wired into the existing lathe controls.

Good luck! Andrew

[Olaf Vogel]

So its turns out I needed to learn a little more about electricity. Rats...

My house is only single phase (I had no clue), the original motor is 1ph, so is my back up. And it seems the VFD's won't output single phase at the 3 hp level. So becoming much wiser... it seems that I'd need a 3 ph motor in order to hook up a VFD.

New 3ph motors seems pretty common. I which case I'd buy a new one and sell the other two I have.
Is there any special requirement I should look for in a new motor? I.e. I've heard about Inverter duty etc, or is that just marketing?

Thanks


However, the lathe is running and I'm finally turning. Its a great feeling being able to work on something larger, without any vibration and make deeper cuts without sloooowwwwing the lathe to a crawl. So far I haven't even been able to make it hiccup. But I've only done 2 small projects so far: 12" dia tree trunk is the largest and it only took 45 in to turn it into a decent bowl. A lot more fun than before!

There's a few little things to sort out
- finding a scroll chuck that fits the 1.5" 6 TPI thread.
- the tool rest adjust is clunky and hard to change - have to get underneath to
- I really want to get the dust collector going. Its a small shop and in the Canadian winter, its tightly sealed, so the dust can get really nasty.

I also had to raise it up 6". I'm 6'2" and the previous owner was much shorter. My girlfriend walked in while I has hoisting it up with car jacks and shoving timber underneath. She took one look and back out. Now its at a comfortable level.

[John E Wallace]

You can use a Rotary Phase converter to run the 3hp 3 phase motor, my brother and I installed one a few years ago on a metal lathe in his shop. Give the folks at Phase-A-Matic's a call at 1-800-962-6976. 3hp is the max for the converter that I helped install. It was about $600. The advantage to the rotary converter is that you do not loose any HP. There web page is http://www.phase-a-matic.com/

John

[Neil Strong]

- 17.5 amps, a little more overhead - not sure I really need that


Can't comment on your particular application, Olaf, but know from experience that one of my 3HP 3Ph (415v) motors peaks up around 17 amps on start up before settling back down to just a few amps while running under low load. If your controller is not rated to handle that peak it may trip out on start up even though it can handle the amps during use. Most controllers have an overload capacity (I think the one you listed is rated at 150% for 60 secs) to cope with start up peak load. If you have 3Ph power in your workshop, I'd be installing your 3HP motor on the lathe and measuring the amperage with a tong meter to check what your current profile is before buying a controller.

BTW, you won't use much more power by installing a more powerful motor if the demand on it is less than its full capacity.

[Dan Hintz]

You can use a Rotary Phase converter to run the 3hp 3 phase motor, my brother and I installed one a few years ago on a metal lathe in his shop. 3hp is the max for the converter that I helped install. It was about $600.
For $600, I'd install a really nice (and efficient) 5HP Hitachi VFD and still have enough left over to take me and my buddies out for quite a few drinks.

The advantage to the rotary converter is that you do not loose any HP.
And you don't lose any with a VFD, not to mention it's a higher efficiency than a static converter.

[Andrew Frandsen]

Hi Olaf,

My shop is single phase only as well and the beauty of the VFD that I purchased is that it takes 220v single phase and outputs it to 3ph to run my 3hp motor. The motor cost me $140 and the VFD was $350 plus HST. I am not far away from you in Welland so if you would like to check it out you are more than welcome to come by.

Cheers, Andrew

[Dick Strauss]

Olaf,
I'm not sure if you have single phase or 3ph power available to you from your comments. The largest motor that I've seen recommended from 220V 1ph is a 3hp motor.

If you use both the VFD and pulleys, you'll have the best of both worlds...more torque at lower rpms via the pulleys and fine speed adjustment via the VFD.

You can power a 3hp/3ph motor from single phase 220V using a VFD as long as its FLA is under 10.5A in the case of the FM50 203-C (my 3hp Marathon motor draws 8.4A). This unit uses a single phase 220V @ 20A input and outputs three phases at 10.5A. I bought the FM50 203-C here for $185 http://www.factorymation.com/s.nl/it.A/id.198/.f.

When John W. stated
The advantage to the rotary converter is that you do not loose any HP. This does not apply to new VFDs. I think John was making the argument of a rotary phase converter vs a static phase converter versus. Also rotary phase converters don't allow you to change the motor speed via frequency.


Take care,
Dick