Low-speed with high torque 3

[Juleen]

Hello, I am new here and don't know much about motors but I hope you could be kind enough to help me find what I look for.
I need a 240V electric motor with 5+ Nm of torque. It will run at 0-180 rpm and I wonder what kind of motor I should use that has that torque no matter what speed it's running at. 5x5x5 inches size or smaller would be nice.
Not sure about what to use for adjusting revs of the motor, preferably something small enough to fit in a hand-held unit.

As you can tell I'm clueless about this stuff which is probably the simplest thing in the world to you guys, but I don't know who else to ask so please bare with me.

A list of what specs the motor I need would be lovely.

Thanks

 

[itsmoked]

For that torque at 180RPM => 1/7 HP or 100W

You are going to have a problem with varying the speed of a 100W AC motor.

That puts you below common 3 phase motors and the VFDs that can control their speed.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[sreid]

Possibly, an electric bicycle hub motor. These are low RPM, high torque brushless motors. The motor speed controllers are usually integrated with the battery pack but the battery pack could easily be replaced with a simple unregulated power supply, i.e., stepdown transformer, rectifier, capacitor bank).

 

[Juleen]

What do you think of this?

http://www.bodine-electric.com/Asp/...Name=48R-F Series Parallel Shaft AC Gearmotor

So many motors to choose from there.

 

[itsmoked]

What do I think?

I think anything with Bodine written on it is one solid unit.

The three phase 0641 would certainly provide the twist and speed you need. Then you need a VFD to turn it down since you stated 0 rpm in your original question.

It sure misses the 5" requirement being 11" long.

What are you building?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScottyUK]

"...torque no matter what speed it's running at..." basically a servo motor if you include a requirement for torque at zero speed. I'm pretty sure you'll get a DC servo in that size which can deliver the power you need, it will just cost you a fair bit of money.


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If we learn from our mistakes I'm getting a great education!

 

[Juleen]

Thank you so much for the replies! I'm afraid I can't tell you what I am trying to build <blush>

The motor being 11" is ok, if you say it has enough power then I'll go for one of those.
What is a VFD?

 

[electricuwe]

If you do not want to use a geared motor, the term for this kind of drive would be "direct drive"

For speed variation you will for sure need some kind of inverter.

 

[itsmoked]

Not inverter.. VFD please.

Juleen; You need to look up VFD or Variable Frequency Drive.

Get educated on the subject if you are contemplating one. Come back with a specific question/s.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Juleen]

Alright. I have been doing some reading and got another question.
If I understand correctly a DC motor is easier and cheaper to speed control than an AC motor. I thought of two things to do.
A power supply thingy from a computer and then use a 12VDC motor, or wiring a 180VDC with bridge rectifier (25+ amps?)and capaciror (3+ uF?).
I've found lots of nice 110 and 90 motors but since I got 230 in the wall I guess I can't use those.

So to the new question, gentlemen! Would it be a good thing to get one like this

http://www.grainger.com/Grainger/items/6ML58

..and operate it by a simple €10 fully variable fan speed control?

 

[Skogsgurra]

Yes - or no.

It depends a lot. First, a €10 fan controller usually is triac based and produces phase controlled AC, which obviously doesn't suit a DC motor. So you need to add a rectifier, which is cheap and easy. But that will cause lots of ripple, which is harmful to the brushes and the collector. So you may need some filtering (smooting) using a fairly big capacitor. And that will (perhaps) overtax the triac since it needs to charge that capacitor 120 or 100 times per second. Probably 100 times, since 230 V usually means 50 Hz.

You simply need to test it in your application to find out what works and what doesn't.

Why do you blush? Trying overunity? Are you? Then you shouldn't only blush - you should be red as a cooked lobster...

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[sreid]

A 180 VDC SCR rated motor is actually run from 220 VAC Full Wave Rectified. These can be speed controlled with phase controlled SCRs. To get to your speed range, use a 10:1 gearbox. These are available from a number of manufacturers.

 

[Juleen]

Thank you so much for the help!
"220 VAC Full Wave Rectified" What does that mean, sreid?
You saying I should use a rectifier but no capaciror?
Please excuse the newbie questions, I am doing my best to learn.

I changed my mind about motors, I'm gonna but one of these Leeson. Says they are SCR rated.

http://www.electricmotorwarehouse.com/leeson/gearmotor/M1135106.htm

I guess the 250rpm would be a better choice than the 165rpm, since the 250's gear ratio is 10?

"These can be speed controlled with phase controlled SCRs"
Could you explain that with words newbie understands? And perhaps show me a link where to find one of those thingies

Juleen

 

[sreid]

In the link you provided for the motor, there is a link for "DC adjustable Speed Drives." You should purchase one of these.

A DC Motor's speed is determined by the average voltage applied. 220 VAC has +/- 300 volt peaks. If this is "Full Wave Rectified (meaning the negative part of the waveform is flipped to the positive side)", the average voltage is about 180 volts DC. If SCRs are used to do the rectification, you can delay the time that they conduct (phase) and reduce the average voltage the motor sees.

 

[Juleen]

I love you guys! Thank you so much!

Just one more thing then I'll leave you alone I promise! How strong rectifier and capacitor would you recommend?

 

[Juleen]

No wait.. the little box does both rectification and speed control?

 

[rtronics]

Maybe I am missing something, but perhaps you could look at an exercise treadmill motor plus controller, also gearbox?

 

[Juleen]

sreid? Help pretty please

 

[sreid]

My guess would be is that tread mills use a VFD (Variable Frequency Drive) to control the speed of a three phase induction motor which drives a gear box. This combination has a much longer life than a DC motor (Brush Wear). You might find what you want at Automation Direct.

http://web4.automationdirect.com/adc/Home/Home

 

[sreid]

Another good source for induction motor gear motors is Oriental Motors.

http://www.orientalmotor.com/products/ac-motors/