Help with motors and controllers

[justaccord]

I am totally ignorant of things electrical. I have a new Vicmarc mini-lathe (VL100) and need to power it.

1. Should I get a DC motor and variable speed controller such as sold by Craft Supplies or an AC motor and VFD (the combination of which would appear to be several hundred dollars less expensive)?

2. If the choice is AC and VFD, (a) how do I match the controller to the motor (b) should I get a 3-phase or 1-phase motor and (c) 220v vs 110v?

Hoping some of you technical sophisticates can talk down to me enough so I can understand it. 🙂

Thanks in advance.

Dave

 

[robo hippy]

I have a Jet 1220VS which has a 3/4 hp DC motor on it and it works surprisingly well (99% of my turning time has been on big lathes). For a mini lathe, I think that is all you need. If you want to go big like PM or Robust size, then a 3 phase, 3 hp motor on 220 is what you want.
robo hippy

 

[Bill Boehme]

For a mini lathe, the DC motor and variable voltage control (which is essentially the same thing as a light dimmer) is the simplest and cheapest way to go. You need to be aware, however, that there is a significant performance penalty when using an electronic speed control vs. using a stepped cone pulley arrangement. If you are willing to accept the performance trade-off of very little power at slow speeds which goes along with the convenience of changing speed with the turn of a dial as opposed to having full power available at all speeds for a mechanical pulley speed control then it is an acceptable option.

 

[CBSears]

Dave,

As I recall, the VL100 is a pretty solid lathe with a 12" swing - more so than most of the popular mini/midi machines. I also believe Vicmarc offers this machine with a 3/4 HP motor.

Although the options you list are probably OK, a third option is to simply buy a 3/4 HP 110 single phase/single speed motor. That's probably your simplest, fastest and, by far, least expensive choice.

Your second option is workable, but it isn't going to be cheap and there is a fair amount of complexity involved in both hooking-up and programming the VFD. Do your homework before you buy. (Pay attention to details like motor frame size to be sure the thing will fit where you want it to go, the shaft diameter fits your pulleys, etc., etc.) Make sure you have a good understanding of what needs to be done, and above all identify and call several candidate companies and talk to their tech support folks before you buy. You want to be comfortable that they are willing to help you, when you need them. (Most of these guys are used to speaking with engineers - caveat emptor!) (You can also search this and other forums for folks who have undertaken projects like this and learn from their mistakes.)

Either way: best of luck and let us know how things go.

 

[john lucas]

Having done all of the above I prefer the VFD. you can get them in 110 versions up to 1 or 1 1/2hp. I found the settings on the VFD as they came from the factory were just fine so i didn't have to set any, although I did play with electronic braking and ramp up times. I prefer the VFD because you have much more power at the low speeds.
DC variable speed is inexpensive if you don't want much power. Penn State Ind. has a kit for $100. I have not purchased one of those but I've heard they aren't bad. You do lose a lot of power at the slow speeds. If you can go the extra money buy 3/4H DC motor, then you won't suffer quite as much on the low end.
Step pulleys and 3/4H motor work great. I have that on my old Nova Comet. I tend to use mini lathes on 1 speed for most projects. On my big lathe I prefer variable speed.

 

[robo hippy]

Hmmmm, just thinking here. With my Jet, it has six pulleys to vary the speed range and the DC motor. If you change the pulleys, you can go pretty slow and lose very little power/torque. This could be more of a problem if you have only 2 or 3 pulleys, like on the PM or my Robust. Haven't tried that kind of set up though. I did try a Nova before the DVR which had 6 or 8 pulleys and the DC motor (1 hp or more, can't remember), and didn't have torque issues, but I never really had a chance to push it to its limits.
robo hippy

 

[john lucas]

That's why I changed my Nova from DC to VFD. I first had the AC motor which eventually broke it's shaft which was common with these lathes. I replaced it with a DC motor but honestly can't remember if it was 3/4 or 1 horse. Turning large platters I would frequently stall it at the lower speeds. I switched to a 1 horse 3 phase VFD and didn't have any issues. In fact the production turner that I sold it to still uses it.

 

[Steve Worcester]

A DC motor with a speed controller is more likely to have torque issues at the bottom range than an AC 3 phase with VFD.

The use of more pulleys mitigates this a bit because it will lower the range on each pulley set.

 

[Rick M]

I am totally ignorant of things electrical. I have a new Vicmarc mini-lathe (VL100) and need to power it.

<snip>

2. If the choice is AC and VFD, (a) how do I match the controller to the motor (b) should I get a 3-phase or 1-phase motor and (c) 220v vs 110v?

Hoping some of you technical sophisticates can talk down to me enough so I can understand it. 🙂

Thanks in advance.

Dave

You didn't indicate whether you plan to use this lathe in a home-based workshop or a commercial building. Homes are typically wired with only single-phase ~220v power tapped at the center to produce 2 "legs" supplying ~110v. Your electric utility would charge handsomely not only to install 3-phase power and the appropriate metering where it's not already supplied, but also for it's use at a higher commercial rate.

For home-type use, single-phase 220v motors are employed to produce higher horsepower at lower current (amps) than could be accomplished using a 110v motor.

 

[Steve Worcester]

What a VFD does is to allow three phase out to the motor. This is what gives you variable speed.

 

[john lucas]

Ditto what steve said. You are using a 3 phase motor but the VFD converts the 110 or 220AC single phase to 3 phase. Without getting into all the tech, it changes the frequency so you are pulsing the motor with more or less full power even at slow speeds. This is why they seem to have more pull at low speeds than DC. DC controllers change the speed by changing the voltage going to the motor, which makes it weaker as you slow it down.

 

[Rick M]

Ahh-h-h, technology. 'Tis a wonderful thing. Thanks for that bit of enlightenment Steve and John.

 

[justaccord]

Thanks!

Your replies have been extremely helpful. I am beginning to get a turner's smattering of electrical knowledge (even though a little is definitely dangerous). Thank you all for the information.

It turned out that a friend of mine had a 3/4 horse 180Volt DC motor at a not-to-be-turned-down price. With that and a new DC controller, I ended up at less than the cost of a new AC motor alone (before adding the VFD).

I bought the controller from a local motor store the owner of which came highly recommended. He said the motor was excellent (made in Indiana) and should have excellent low-speed torque.

Without this option, I probably would have gone for an ac motor with or without vfd.

Even VFD can have torque problems, though, in my experience. I have stalled out my 2 hp Powermatic several times while roughing out bowl blanks. I doubt I will turn anything with similar torque issues on the mini.

Dave

 

[Steve Worcester]

It turned out that a friend of mine had a 3/4 horse 180Volt DC motor at a not-to-be-turned-down price. With that and a new DC controller, I ended up at less than the cost of a new AC motor alone (before adding the VFD).

I bought the controller from a local motor store the owner of which came highly recommended. He said the motor was excellent (made in Indiana) and should have excellent low-speed torque.
Dave

What do you use for a power source that will give 180V DC?

 

[kenvalaska]

What do you use for a power source that will give 180V DC?

220 volt single phase AC -- 120 results in about 90 volts DC or less.


Ken in juneau

 

[justaccord]

The DC motor just plugs into 220. More precisely, it will be hard wired to the controller, which will plug into 220.