Vector Control of AC Drives

[khan]

Is anyone familiar with using Variable frequency drives (VFD) to control AC motor speeds?? Seems to be cheaper than using DC with a controller.
The control for a 1/2 hp AC motor runs about $100 or so. Maybe im missing something but man they seem really smooth and precise.
This is the page i was looking at but i just did a random search ... i dont really know where the best place to buy would be.
https://www.automationdirect.com/adc...ontrols/Drives

[Mute]

What are you controlling?

[Mute]

What are you controlling?

Ha, you must think this a place to get shit done.

Counter productive is the name of the game IMO.

Goes like this
1. Never give someone the direct answer.
2. Repeat step 1.
3. Reap benefits.
4. Deny
5. Repeat step 4.

[Cerberus]

Those drives are for controlling 3 phase 230VAC motors, not 115V household motors. That is significant.
I have not used this type of controller and don't know what other components are required, if any.
If you are working with 230/3Ph then you should call the application assistance and see what is required. I'm sure it's more involved than a dimmer switch but do not know to what extent.

[Mute]

Those drives are for controlling 3 phase 230VAC motors, not 115V household motors. That is significant.
I have not used this type of controller and don't know what other components are required, if any.
If you are working with 230/3Ph then you should call the application assistance and see what is required. I'm sure it's more involved than a dimmer switch but do not know to what extent.

The page had them in various models.

They have single phase 120 available. Yet they are significantly cheaper at 59$. But I'd guess he needs 3phase since that was the price point chosen.

[Mute]

I bet if we can get Mr.$essions or the committee of fools in here, I'm sure all the questions will be answered.

[khan]

Well i was thinking about someone wanting to set up like a Beth 100 or something similar or even a bigger lathe ...
THe DC controllers are pretty expensive and i had just never seen an AC control that gives you all the options of DC...
Would be a great way to set up a lathe because you wuld be using a AC motor and they are pretty cheap by comparison,

Khan

[khan]

After reading all the responses im reminded why we have the Higher learning page.
Probably should post it there.

Khan

[Mute]

Well I'm sorry if I made this experience a bad thing. All I can say about that higher learning thing, is that you are limiting your possibility of ideas and input.

Regardless of how obnoxious or how much of an asshole I am, my intent is always to get the job done.

Simple as that.

And I get flack about that all the time here. From day 1.

Love this place, don't get me wrong. But people expect me to act differently than they themselves do and that's not how I work. I treat others like I want to be treated.

[somewhere]

A dc motor is a better solution for slower speed operations, no loss of torque all the way down. Think treadmill motors and speed controls they can be had through different surplus places or on eBay I'm sure. Second option would be 3 phase with a vfd. Last would be an oversized 220 volt single phase motor and a vfd that way when you lose 75% of the power it can still turn.

[Greymatter Glass]

What? Quality DC motor and American made controller for under $400? Sure, why not!

https://www.automationdirect.com/adc...se_(up_to_2HP)
https://www.automationdirect.com/adc..._50V)_Enclosed

I have a little 1/3hp setup on my F lathe, even down at <20RPM it takes some effort to stall the motor out.

[snoopdog6502]

Most ac motors will over heat at slow speeds that is why so many use step pulleys.

Go DC or 3 phase and VFD. 3 phases motors are better for all day every day use. 3 phases motors are cheap because lots of people cant use them.
Good deals at industrial auctions.

I built a wood lathe with an AC motor and it is limited in speeds, I can add a jack shaft for a low,low speed. Any electronic speed control would make the horse power drop to nothing.

[PyroChixRock]

After reading all the responses im reminded why we have the Higher learning page.
Probably should post it there.

Khan

If you'd like me to move it I'd be happy to.

[khan]

Misha... I think those involved have taken a more serious tone
so its probably good .

but thanks..
Khan

[khan]

Thanks Snoopdog thats what i was wondering. I had never seen a VFD and i wondered if that was something new they had just come out with.
All my variable speed machines use machanical control of the speed so i suppose that hasnt changed as the best approach.
Khan

[khan]

What? Quality DC motor and American made controller for under $400? Sure, why not!

https://www.automationdirect.com/adc...se_(up_to_2HP)
https://www.automationdirect.com/adc..._50V)_Enclosed

I have a little 1/3hp setup on my F lathe, even down at <20RPM it takes some effort to stall the motor out.

Very cool Greymatter... !!
That has to be the best option.

[BurntHands]

I use a big 3 phase motor with an ac speed control on it on a Steinert lap wheel, the motor control just controls the hz between like 10-60hz but it's smooth and torquey through the range but the motor's huge. The digital controller has a weird braking system too, makes weird noises. I don't need it to reverse or anything but it works good speed up/down, not as good as a knob.

I have a few other projects I could use a variable speed motor for, I've got a treadmill ripped apart but haven't found an easy way to rig up a speed control, been eying up Chinese ones. Good timing, thanks.

[Cerberus]

I don't see that there is a right or wrong answer or way to go about powering a device.
One could make the argument that time = money and base a decision on that. AC drives may be less expensive up front but it depends on your skill set to determine the VALUE of each option.
In my case I would likely need to spend a day or two figuring out programming a VFD but a DC control I would have running in a couple of hours. I would find more VALUE in the DC price because I would spend the weekend melting glass instead of swearing at a little plastic box of wires. If you really like electronics or learning new tech then you may find more VALUE in the project than the glass.
If the cost difference was a couple grand then I may put effort into learning the VFD but for a couple hundred bucks difference I would do what I am familiar with, especially because I don't have tons of free time.
If you don't know either then the DC option will be the quickest way to an operational device (short of buying a turn key machine). The VFD doesn't appear to be plug n play but DC is exactly that.
Depends on your situation.
With Dougs link I may dust off my lathe idea this summer, that's pretty affordable!

[somewhere]

Skycraftsurplus has treadmill 1,200 watt motors with dc to pulse width modulators for $30. I bought a few of them. If you need to slow it down to a crawl you may have to add resistors in line. These are imo perfect for lathe or mill operations. Hands down one of my favorite semi local picks. I was in there last week and closed the place down. Ended up spending less then a bill for more stuff then I should be allowed to own.

Google skycraft surplus treadmill motor and you should find it.

[snoopdog6502]

Lots of home machinist buy treadmill motors and run them with Pulse Width Modulator to power small lathes and drill presses.
Pretty darn cheap way to go.

I have been doing a lot of research and window shopping for motors and controls for machine tools Im building and possibly making my recumbent trike electric.
Iv made a glass grinder, a belt sander and a wood lathe in the last couple months.
Possibly powering and charging everything from solar power. Off grid machine shop if you will.

The units Greymatter Glass linked are realy good in price.

I would not bother with the variable frequency drives till you get into 3 HP or above and feeding 240V. Way more then a typical glass lathe would need.