I've done a similar thing Strantor, and 500 RPM is totally unsuitable for a 20k RPM universal motor. The nature of series would motors makes them have very low power and/or unstable when under about 1/4 of their normal RPM.
You really need a DC motor, pref a shunt wound or perm magnet type. There are a lot available including treadmill motors which are specifically designed for fairly low RPMs.
And even with a DC motor 500RPM is far from ideal, so you are better with a DC motor at (say) 1500 RPM and 3:1 reduction gearing. What are you driving?
All motors run in the thousands.I've been told elsewhere that treadmill motors are also fairly high RPM (in the many thousands).
500 RPM is totally unsuitable for a 20k RPM universal motor. The nature of series would motors makes them have very low power and/or unstable when under about 1/4 of their normal RPM.
I have used triac control on a small Unimat lathe with a universal motor. In my opinion, triac control is almost totally unsuitable for speed control on a lathe because of the torque issue.
Of course, the universal motor can also be run on DC. We're experimenting here, so why not build a beefy rectifier/filter circuit and follow it up with a PWM speed control just to check things out. If it works well enough, you can add the speed feedback/control later.
Given your rough dimensions and weights you plan to run I doubt that a 1/2 Hp Dc motor is going to be anywhere near capable of running your lathe unless you don't mind only being able to take a few thousands of an inch cut with each pass which gets old really fast.
I have a Smithy 1340I Lathe/Mill combo unit that came with a 2 HP DC motor from the factory. It was crap and I killed it and its overly complicated speed control unit after only a few dozen running hours. After that I switched it over to a full VFD unit and 2 HP three phase motor which made a world of difference in the low end power and speed control aspects plus a good VFD unit has loads of programmable functions including ramp up time, ramp down time, auto reverse, upper speed limit, lower speed limit, timed torque boost, and external potentiometer based speed control interface.
I for one vote for three phase motor and VFD unit if you are looking for sustained high torque and low RPM operating capacity.
A good used 2 Hp four pole (1740 RPM) three phase motor will set you back about $20 or less and a good used VFD to run it can be anywhere from free to around $100 at most.
What I meant was, I need to step up 220V (1ph) to (minimum) 380V or (optimal) 480v.Actually going from 380 to 480 is cheap and easy.
I agree, I don't. Ebay is my source, and I haven't seen anything near those prices on ebay. Any pointers where I should be looking?As far as getting the motors and VFD units apparently either you don't know the right people or the right places to look!
**broken link removed**
Search on VFD Drive and list by price. There are quite a few new ones for less than $100 that take single-phase input.
The reason I didn't know that these inexpensive drives exist is probably because when I searched for them previously, I was probably searching by brand name for drives that I was familiar with (Allen Bradley, Yaskawa, Emerson, Eurotherm)let me warn you that the Huanyang drives are very low quality and I've personally had trouble with them and know of others the same.
I would strongly recommend you buy the VFD in UK,
It's a metal lathe and I plant to be able to thread on it. That area (driving of spindle VS lead screw) is still up in the air right now. I'm thinking I might do it seperately, with a servo on the leadscrew. Not quite sure, have to look into my options for gearing.Edit; BTW, is this a wood lathe or metal working lathe you are building? If metal, will you have threading capability?
I don't know. maybe 2 acme nuts with a spring between them? Can you tell me how does it effect, so that I can use this information to decide?Will you use half/split nuts on the lead screw? If you need instant stop, that may affect your choice of control type.
John
I don't know. maybe 2 acme nuts with a spring between them? Can you tell me how does it effect, so that I can use this information to decide?
Ok, So for the time being I'm 100% sold on the idea of using DC. I trust you guys and your first hand experience, but I've been digesting your comments for the past half day and I'm wondering (theoretically) why the universal motor with triac control at low speed is a no-go.
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