Replacement motor w/ higher rpm/VFD

Awl--

I acquired this incredible Engleberg 4" pedestal belt sander, but w/ shot motor, shot driveshaft, on which I've posted elsewhere.

The replacement motor is proving to be a problem. Direct replacment is possible, but expensive. (Cast iron finned, 1700 rpm, 143 frame). Rewinding is expensive.

But I've been finding possible motors, but w/ 3450 rpm, 3 ph, 1 hp.

Would this motor on a VFD be a viable solution? As a direct drive unit, I don't have the luxury of mixing pulley ratios, so would torque be a problem, at dialed-down speeds--actually, 50% speed? Would the higher speeds be any advantage for some materials??

What are people paying for these sized VFDs? TIA!

---------------------------- Mr. P.V.'d formerly Droll Troll

Reply to
Proctologically Violated©®
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I have a pair of Hitachi 1hp VFD's on my lathe and mill. They were NOS and were about $100/ea They work fine.

That said, a VFD would probably work. I have no problem with torque at 50% speed.

OTOH, I'd be scared shitless that some sort of malfunction or missuse would give the motor

100% speeed, or worse - 150% or 200% speed and detonate the wheel...
Reply to
Jim Stewart

What is "NOS"? Where'd you get'em from?

---------------------------- Mr. P.V.'d formerly Droll Troll

Reply to
Proctologically Violated©®

New/old stock. Old stock that has never been used.

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Same seller I've done business with, no problems.

Reply to
Jim Stewart

You did not say what the original motor horsepower was, but a 1 horsepower

3450 motor will have half the torque that a 1 horsepower 1700 RPM motor does, because torque, motor speed, and horsepower are all related. The motor is designed to supply the nameplate horsepower at the full rated speed. If you slow the motor down with a VFD, the torque will be the same at a lower speed, or nearly the same, but the calculated horsepower changes. If you are running the motor with encoder feedback and a vector drive, you will have more torque available at very low speeds than if you are running open loop.
Reply to
John Busby

If you install a 1HP 3450RPM motor and run at 1725RPM you'll only have

1/2HP available.

Is the trouble you're having locating a motor a result of the combination of the CI frame and 143 frame size? I believe a 145 frame differs only in that the mounting hole spacing parallel to the shaft is a bit greater.

You can get a basic (non-programmable) VFD in the 1HP range for under $200. You should be able to get a good used drive for under $100. If you do buy a used drive, make sure you get the required parameter unit/programmer/display with it, and that a manual comes with the drive or is available online.

Ned Simmons

Reply to
Ned Simmons

I'm no expert by any means, but when looking into this solution for replacing a DC spindle drive on a CNC lathe with an AC drive the big problem would be the loss of power at lower rpm. I.E. the slower the motor went, while maintaining constant torque, the lower the HP delivered to the spindle. Now, VFDs have progressed much since then. It may be that the torque will be doubled with the halved RPM. If that's so then then it's all good, just provide enough cooling with an extra fan. But, if the torque remains the same, HP will be half. If you need the full 1 HP at 1750 rpm then maybe a two HP 3 ph motor would be best. ERS

Reply to
Eric R Snow

If you need 1 HP at 1700 RPM, then get a 2 Hp 3450 RPM motor and a 2 or

3 HP VFD. (2 HP is fine if you have 3 phase power, 3 Hp is better if you are going to run it on single phase.)

You can probably get the VFD for less than $150 on eBay or Dealers Electric. Maybe a LOT less, it just depends on who is selling at the moment.

Jon

Reply to
Jon Elson

Probably not a good idea -- but slower speeds might be an advantage at times -- for certain plastics to prevent melting.

But most VFDs have the ability to set a maximum allowed frequency (you have to spend some time in the manual to find which parameter to change and how to change it), so there would be no risk of running at 200% speed.

Enjoy, DoN.

Reply to
DoN. Nichols

Sounds like a plan. Cupla people have mentioned programmable/vector drive stuff. I would imagine this "costs extra". Is it worth it? Is there anything ito of older/cheaper VFDs that I should avoid?

---------------------------- Mr. P.V.'d formerly Droll Troll

Reply to
Proctologically Violated©®

Probably not for your grinder. True vector drive requires encoder feedback and is desirable when you require full torque at very low RPMs, or accurate speed control. Sensorless or flux vector control is a compromise between V/Hz drives and true vector drives and is included in many low cost programmable drives these days.

The programmable drives will have literally hundreds of settable parameters that you don't need if all you want to do is turn your grinder on and off with a switch and change the speed with a pot.

Some of them generate more electrical noise than newer or higher end drives. I'm a big fan of Yaskawa drives. Both the older GPD series (which you may see with a Magnetek label) and the newer V7/F7/G7 drives are good solid drives and are well documented. Mitsubishis are also generally very good, but the documentation can be cryptic.

Ned Simmons

Reply to
Ned Simmons

If you're repairing the unit to put it to work for your own use, you could probably fabricate a mount for a common 1725 RPM TEFC motor and use a coupler to connect it to the input shaft.

Almost any good quality 1/2 to 1 HP motor should be adequate for a belt sander, depending on how big the parts are that you want to grind/sand. Don't be too easily impressed by HP, a 1/2 or 3/4 HP motor delivers a lot of power for a belt sander.

TEFC is highly recommended because the grinding dust will get into a open-frame motor.

If you decide you need other speeds, a jack shaft can be added to almost any application with some parts and additional base plate area. Otherwise, you might also consider a variable speed DC drive.

WB ................

Reply to
Wild Bill

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