Is there too slow of a motor speed?

blackhawk357m

blackhawk357m

AzB Silver Member
Silver Member
I just bought and mounted a 1021W Marathon Motor 115v 60 HZ 1725 RPM 1/4 HP, 1/2" shaft to power my spray booth station. I hooked it up to a variable speed router control box.

Is it possible to spin the motor too slow and burn it out?


Thanks,
Nathan
 
blackhawk357m said:
I just bought and mounted a 1021W Marathon Motor 115v 60 HZ 1725 RPM 1/4 HP, 1/2" shaft to power my spray booth station. I hooked it up to a variable speed router control box.

Is it possible to spin the motor too slow and burn it out?


Thanks,
Nathan
Click to expand...

Yes, anything slower than 1725 rpm will be detrimental to the motor. To economically run a motor slower than it's listed speed the motor needs to be a DC or an AC/DC motor. To run a slower rpm for a spray booth it's best to get a small gear reduction motor or slow the system down with different size pulleys or you could go with a DC system and have variable speed.

Dick
 
blackhawk357m said:
I just bought and mounted a 1021W Marathon Motor 115v 60 HZ 1725 RPM 1/4 HP, 1/2" shaft to power my spray booth station. I hooked it up to a variable speed router control box.

Is it possible to spin the motor too slow and burn it out?


Thanks,
Nathan
Click to expand...

Does it work?

Speed controls and most AC motors don't make good neighbors. Usually, the only way to control the speed on an AC inductions motor is with a Variable Frequency Drive. The motor gets its speed from the number of poles on the armature, and the frequency of the line current, which is a constant 60 Hz. A VFD can alter that frequency up and down to control the motor speed.

Royce Bunnell
www.obcues.com
 
RBC said:
Does it work?

Speed controls and most AC motors don't make good neighbors. Usually, the only way to control the speed on an AC inductions motor is with a Variable Frequency Drive. The motor gets its speed from the number of poles on the armature, and the frequency of the line current, which is a constant 60 Hz. A VFD can alter that frequency up and down to control the motor speed.

Royce Bunnell
www.obcues.com
Click to expand...

well, lol, it spun. But after a little bit i noticed that the motor was getting pretty hot so I shut it off and haven't turned it on since. Then I posted my question. I guess I'm gonna try to find a DC motor, and maybe try to sell the AC one I tried. Oh well, live and learn :o
 
RBC said:
Does it work?

Speed controls and most AC motors don't make good neighbors. Usually, the only way to control the speed on an AC inductions motor is with a Variable Frequency Drive. The motor gets its speed from the number of poles on the armature, and the frequency of the line current, which is a constant 60 Hz. A VFD can alter that frequency up and down to control the motor speed.

Royce Bunnell
www.obcues.com
Click to expand...
What would the negatives be of using a VFD on a standard AC motor be?
 
cueman said:
What would the negatives be of using a VFD on a standard AC motor be?
Click to expand...

I am no expert but running a standard AC induction motor that was designed for 60Hz/1750rpm at a much slower speed might cause motor cooling problems. Running it too fast might reduce bearing life. Note that this is not the same cooling issue as the OP noticed by simply reducing the voltage to the motor. In that case the current goes up significantly and you get big-time heating of the windings as a result. Using a VFD won't drive up the current, rather the "heating" is caused by a lack of cooling as a result of the motor spinning slower.

Also standard AC induction motors typically do not have a rotary sensor for feedback to the VFD (no tachometer), so maintaing a constant speed under variable loads is difficult.

Dave
 
Last edited:
cueman said:
What would the negatives be of using a VFD on a standard AC motor be?
Click to expand...

The cooling issue(if there is one)can be controlled with a fan(of course). The motor itself needs to be 3 phase to start with though. The only negative I can think of is the added cost.

I believe Monarch's revered 10ee's had some sort of drive didn't they?

I am starting to see newer manual lathes come out with variable drives.

I have some vfds here and when I get well enough, plan on hooking them up proper. That would mean with pots to control the spindles, breaking, custom ramp speeds....ect....ect. I don't plan on running the spindle much over 2500, even though I think my chuck can handle 3k. It is pretty scarey seeing it spin 2k.
 
cueman said:
What would the negatives be of using a VFD on a standard AC motor be?
Click to expand...

You know Chris, I'm not sure.

All I know is that the VFD's that I'm familiar with, and that's not really too familiar, all output 3 phase. You can get single phase or 3 phase in, but they all output 3 phase. I guess it would work on single phase, but the VFD would have to be the right one, of course.


Royce Bunnell
www.obcues.com
 
blackhawk357m said:
I just bought and mounted a 1021W Marathon Motor 115v 60 HZ 1725 RPM 1/4 HP, 1/2" shaft to power my spray booth station. I hooked it up to a variable speed router control box.

Is it possible to spin the motor too slow and burn it out?


Thanks,
Nathan
Click to expand...

The 1725 rpm is fast for a spray booth. You must have slowed it down with pulley ratios.

You have choices..........

Use an AC motor and get a vfd ..... expensive

Use an AC gear motor and use pulley ratios for speed adjustment

Use a DC gear motor and use variable voltage DC to control it... the controller is easy to make using an AC light dimmer and diode bridge rectifier.

Use a treadmill motor and controller. I found one for free on Craigs List. I spin my finish lathe with it.


http://www.surpluscenter.com/electric.asp
http://www.sciplus.com/category.cfm/subsection/18

Kim
 
To the original poster. For the purpose that you stated, I would suggest that you consider a DC motor or a DC gear motor with a variable speed control. They are available is several different sizes. If you are interested or if you have any questions please just let me know. I have some available.

Thanks a Million!!
 
RBC said:
You know Chris, I'm not sure.

All I know is that the VFD's that I'm familiar with, and that's not really too familiar, all output 3 phase. You can get single phase or 3 phase in, but they all output 3 phase. I guess it would work on single phase, but the VFD would have to be the right one, of course.


Royce Bunnell
www.obcues.com
Click to expand...

It has to be 3 phase out and 3 phase motor...
 
whammo57 said:
The 1725 rpm is fast for a spray booth. You must have slowed it down with pulley ratios.

You have choices..........

Use an AC motor and get a vfd ..... expensive

Use an AC gear motor and use pulley ratios for speed adjustment

Use a DC gear motor and use variable voltage DC to control it... the controller is easy to make using an AC light dimmer and diode bridge rectifier.

Use a treadmill motor and controller. I found one for free on Craigs List. I spin my finish lathe with it.


http://www.surpluscenter.com/electric.asp
http://www.sciplus.com/category.cfm/subsection/18

Kim
Click to expand...

Nice links! :thumbup: I found a 72RPM motor with 1/2" shank @ surpluscenter with cap, resistor and the footplate for $33. Think I'll use the step pulleys I got and slow it down more if I need to.

Thank you EVERYONE with your input on this, it was a huge help!! :D

Nathan
 
blackhawk357m said:
Nice links! :thumbup: I found a 72RPM motor with 1/2" shank @ surpluscenter with cap, resistor and the footplate for $33. Think I'll use the step pulleys I got and slow it down more if I need to.

Thank you EVERYONE with your input on this, it was a huge help!! :D

Nathan
Click to expand...


Glad to help.

Kim
 
slow speed motor

i havent tried it yet but a d/c motor out of a old tread mill.
there cheap and almost ever yard sale seems to have one for sale
just a thought
mike
 
Rotisserie motors turn way slow, too slow to shoot finish efficiently.
They do produce some decent torque though.
What this means is that through a series of pulleys, you could provide greater speed
to whatever it is you're driving.
To me, that's a 1/2ass way of going about it.
I've shot finish on a lot of cues & shafts in 23yrs.
For my money, the best system is variable spd. DC w/reverse.
I wouldn't recommend anything else for a spray-booth application.
Get with Todd @ tsp&b here on AZ. He can probably hook you up for under $100.
Go back and re-read post #11.
Do it once and do it right.

KJ
 
Thanks KJ.
I've always held you in high regard for your willingness to share your knowledge and experience with those of us that are eager to learn. Your efforts do not go unappreciated. I may not be posting on these forums, but believe me, I have gained a wealth of knowledge here.
Also, thanks for the cutter! That thing is fantastic!

Cheers!

Dan (the lurker)
 
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