Some Voltage and Frequency Lathe Questions

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Matabele

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Hi guys,

I was wondering if anyone with some electrical knowledge could give me some advice. Im looking to buy a Grizzly G0509G lathe. So the Grizzly is a 3 phase, 120 Volt machine that is designed to operate on a 60Hz Frequency power supply. I would like to import this lathe into South Africa which uses a 220-240 Volt system but runs on a 50Hz frequency. Is it possible to somehow convert or transform the power supply to get this lathe to operate ok in South Africa?

Any advice appreciated thanks!
 
Actually, that lathe is listed at being 220 Volt , 3 phase, 60Hz. Contact Grizzly to find out for sure, but if you have 220 3 phase power, it should run OK on 50Hz, just a little lower RPM. If you only have single phase available, then a Variable Frequency Drive could be used to generate both the 60 Hz and the 3 phase from the single phase power.

Dan
 
Thanks for the reply Dan, yep sorry I got the voltage wrong on the Grizzly. Good news I can just get a VFD to fix the problem. Is it possible to link several machines up to a single VFD, assuming the power requirements are the same or do you have to have a dedicated VFD for each machine?
 
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I run a mill and a lathe off the same VFD (not at the same time). They both have 1 1/2 HP motors, but one is 1725 RPM and the other 3450. I vary the frequency from 10Hz to 90Hz and have never had any problems.
 
Matabele said:
Hi guys,

I was wondering if anyone with some electrical knowledge could give me some advice. Im looking to buy a Grizzly G0509G lathe. So the Grizzly is a 3 phase, 120 Volt machine that is designed to operate on a 60Hz Frequency power supply. I would like to import this lathe into South Africa which uses a 220-240 Volt system but runs on a 50Hz frequency. Is it possible to somehow convert or transform the power supply to get this lathe to operate ok in South Africa?

Any advice appreciated thanks!
Click to expand...

A VFD will work. However: don't just drop a motor designed for 60 cycle current onto a 50 cycle main and expect happy results. There is a very sound basis for the difference in construction (mostly, 50 cycle needs more iron) and you WILL need to derate a 60 cycle motor, transformer, etc if you run it on 50. Same reasoning applies to using a VFD. Your torque and motor performance WILL degrade above and below design frequency. For a home shop, typically light and intermittent loads, likely no problem- but don't expect to run heavy production all day long.

All that understood, why not ask Grizzly to mount the RIGHT motor for your mains? I'm sure it's an option- ask. The GO509G is a 16 speed, gear-head, gunsmithing lathe. I didn't check, but if it's designed right, the 16 speeds (between 45 and 1800 rpm) will be spaced properly (that is, geometrically), and there is no reason to go through all these efforts when a simple motor swap at purchase would solve the entire problem. Yes, I understand the theoretical basis for infinitely variable speed; in practice, machinists have found that correctly spaced speeds -especially in a gear-head drive- give enough range without additional complexity.

Just get the right motor to start with. Especially on a new purchase, doing more is way too complicated.
 
Thanks for your reply GL, appreciate it. I did ask Grizzly about the possibility of swapping motors but they don't offer anything other than what comes as standard (well in terms of motors anyway), so that's not an option for me. Saying that, how much would a properly rated motor cost, any idea? Maybe I could just buy one 3rd party and have it swapped out. It would void the warranty that's for sure, but i guess in this situation there has to be a compromise somewhere.
 
Matabele said:
Thanks for your reply GL, appreciate it. I did ask Grizzly about the possibility of swapping motors but they don't offer anything other than what comes as standard (well in terms of motors anyway), so that's not an option for me. Saying that, how much would a properly rated motor cost, any idea? Maybe I could just buy one 3rd party and have it swapped out. It would void the warranty that's for sure, but i guess in this situation there has to be a compromise somewhere.
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Certainly. I thought you might have asked Grizzly, but never assume! In the US, a 3 hp, 1800rpm, 206-230v 60 Hz 3ph motor (Marathon, a good brand) is around $250 from Dealer's Electric (also a good source of VFDs). A 50 cycle unit should be available in your location for a similar price, perhaps a few bucks more. I rarely buy new equipment (and warranties are short, anyway) so this hasn't been a problem; I routinely swap out motors on older equipment. One point: check the balance. An occasional motor will have a poorly balanced rotor, and can cause finish problems (hard to find, too). Don't forget to match rpm, or change the motor pulley so you actually get the indicated speeds. Fenner (adjustable link) belts can help, too. Swapping out a motor is as simple as making sure the mounting matches (and the other physical dimension are OK. Get a TEFC unit to avoid problems with swarf, if the motor is exposed at all. The control electrics should work (although, if there's a magnetic starter, the contactors will also be a little light on the core iron). Short summary: this should be a trivial fix. If you're uncomfortable with the electrical side, a local contractor should be available to help (and might have an easy source of motors, too. Also- check local rebuild shops; often deals there, especially small 3 phase units).

I'd push a little on Grizzly, too. Or maybe consider getting a Jet/Wilton. Perhaps Grizzly will consider selling a lathe without the motor (doubt it, but can't hurt to ask). This is light industrial/small shop equipment. It's not reasonable that there are no motor options. (Well, it is- because that's the manufacturer's choice- but the lack of options reinforces my general feeling that Grizzly is simply one of the better places to buy Chinese iron...and no more than that). In the same vein, if swapping a motor voids the warranty on the rest of the machine (presuming you don't uprate hp) previous comments also apply.
 
Mr. GL Carlson;

Nicely stated, well phrased reply. Right on point, to the point. Good work.
 
Matabele said:
Thanks for the reply Dan, yep sorry I got the voltage wrong on the Grizzly. Good news I can just get a VFD to fix the problem. Is it possible to link several machines up to a single VFD, assuming the power requirements are the same or do you have to have a dedicated VFD for each machine?
Click to expand...

There have been several good comments on the use of a VFD, so maybe I should expand a little on what I was suggesting - My thoughts were to simply use the VFD as "quick and dirty" way to generate the required 3 phase, 60 cycle voltage from the 50 Hz source - not to actually use the VFD to control the speed of the lathe by varying the frequency. I am essentially using a VFD as a phase converter in my shop, since I do not have 3 phase available (I run a power hacksaw and a lathe off of mine). At this time, it is set to provide a fixed 60 hz output. I may, at some point in the future re-program mine and add a pot to use it to provide a speed control for the lathe, but I have not yet had a situation where it was worth doing. It may or may not be cheaper than replacing the motor, but it does offer another option.

Dan
 
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