help slowing down electric motor

[selmerzodiac]

I recently purchased a dough kneader from france, but it is moving too fast to properly mix the type of bread that I prefer. I originally tried hooking the mixer up to my variac and even when lowering the voltage the mixer speed did not decrease. As I am learning I might need a variable frequency drive, but I have had a hard time finding one that puts out single phase, and I don't want to over buy on features. All I need is a simple device to cut the speed in half (or close to that), and exact speed is not critical. After four hours of calling places looking for one, I figured I should ask someone that knows their stuff if it is even what I really need. Here is what I know about the motor from the manual.
Motor:
Thermal protection, Single phase
110-120 V - 50/60 Hz - 650 W, 6 Amps
1500 RPM (50 Hz) - 1800 RPM (60 Hz)
Speed rotation : 84 RPM (60 Hz).

Let me know if you need any more info on the motor and I will contact the company with specific questions. I would like to thank anyone willing to help in advance, as I in am way over my head here!

 

[itsmoked]

Man.. You are in a tight spot.

There is no reliable way to slow a single phase motor.

Three phase with a VFD is The Way.

Possible solutions:

1) Contact the maker. You cannot possibly be the first to have this problem. They may have a retrofit kit.

2) Use a gearing change. You may have to find a tinkerer who can essentially hack your mixer.

3) Alter your mixing blade to effectively seem like the mixer is running slower. Like remove some center pieces.

4) Figure out if the motor is a standard NEMA frame size. If it is find a 3 phase replacement. There are VFDs that can run on single phase 120VAC and put out 3 phase 240VAC.


Keith Cress
kcress -

http://www.flaminsystems.com

 

[dpc]

Does it have a gear box or a belt drive to get from 1800 rpm to 84 rpm?

 

[selmerzodiac]

wow, you guys are fast! I am not sure if it has a gear box, or a belt drive, but I do know that there isn't much room in there. I am going to check on the possibility of changing out the motor, and try to find out how it gears down. THank you both so much!

 

[ozmosis]

You could try this:

http://www.invertek.co.uk/product_optidrive_e21_products.aspx

They are one of the few companies who offer a 1ph in-1ph out VFD.
I understand they sell in the US via Bardac.
However, make sure the motor is suitable and do not just hook up your power supply of the dough kneader to the VFD as other devices internally could be connected to the same supply and you wouldn't necessarily want a PWM supply from the VFD feeding other devices.

 

[selmerzodiac]

OK, here is a breakdown of the parts inside, so maybe it is possible to gear it down? Not sure who could do that for me if it is even possible.

http://www.santos.fr/images/vuesgif/18C000309.gif

And here is a schematic of the wiring (about half way down page)

http://www.santos.fr/dossierstec/us/18-manu-US-071002.pdf

The wiring looks pretty simple in there. Can you tell from the schematic if I can just hook up the bardac? I am curious to find out how much that costs. Looks pretty fancy!

Maybe a new motor would be the cheapest alternative. I will try to find out from the manufacturer if they can give me more specs. I know they have said that they can't help me to slow it down.

You are all amazing!

 

[jraef]

The motor has a starting relay and a capacitor (the manual has warnings as such) which means you will NOT be able to use any kind of speed control device on it, sorry. It also looks like a very small custom made motor and a small custom right-angle gear drive on it. Unless the mixer manufacturer has some sort of options, you are out of luck I'm afraid. The only possibility would be if you know of an exceptional machinist who can cut custom gears and have him machine gears for you that would change the ration AND fit in that housing. That's an extreme long shot though.




"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[edison123]

How about a rewind of the motor to a lower speed ? Any good motor repair shop should be able to do it a minimal cost. Contact local EASA chapter. (

http://www.easa.com/)

 

[jraef]

Better yet! Why didn't I think of that?

 

[edison123]

One caveat though. By redesigning for a lower RPM, the motor has to be derated and OP has to check whether the new lower HP will meet his load requirement.

 

[edison123]

jeff

We rewinders have to look out for each other.

 

[selmerzodiac]

I use this machine at a much lower capacity than maximum. So far any mixing that I have done has appeared to cause no strain on the motor. It seems over powered (if that's possible). Does anybody have a rough guess as to what a fair price is for a rewind?

 

[ozmosis]

Hmm, as jraef points out, the VFD will not work on this motor.
Can you see a make on the gearbox? I know a company called Parvalux supplied to a few kneading machines in Europe but not sure if this is one of theirs.
You might be a little stuck with fixed speed on this one. Go and buy a loaf
It seems a little strange that a machine whose sole purpose in life is to mix dough and it is not doing that right.

 

[edison123]

selmerzodiac

$300 - 400. But hey, I am from India.

If there is a centrifugal switch or any such speed dervied device/relay, you might have to change that too.

 

[edison123]

That should be $ 30 to 40.

 

[itsmoked]

That is the screwiest looking mixer I have ever seen...

It uses a Pressure Angle Worm Gear (high ratios).

Any changes will cause dimensional issues.

Then they used the motor as part of the structure so changing the motor dimensions will cause immediate issues also.

The only thing I can suggest if a rewind doesn't work for some reason would be a true hack.

You mount a motor parallel to the existing one.
You gut out the existing stator windings.
Cut a hole in the motor case and belt drive the existing armature from the new motor...

Now I ask.. Would it not be easier and cheaper to sell this pile on ebay and buy a better unit there?



Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

If you are considering rewinding, investigate the possibility of rewinding for three phase. Then you can use the VFD.
Overload at slower speeds; The drop in power is mostly from the drop in speed. The torque should hold up fairly well.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[roydm]

It seems to me there is a golden oportunity for some VFD manufacturer to make a VFD specificaly for single phase motors. I see no reason why a typical 3 phase VFD cannot be reprogramed to produce two phases 90° apart One phase for the start winding one for the Run. The start winding phase could have a different set of parameters to match the winding.
Am I out to lunch?
Roy

 

[LaffeyDD724]

Looks like the supply voltage frequency might be the key. The motor data says that it will run 300 rpm slower on 50 Hertz.
Now what could be done to lower the supply voltage frequency?
Maybe you could put together some sort of electronic gadget to to drop the supply voltage frequency.

Tom

None of us is as smart as all of us.

 

[jraef]

t seems to me there is a golden oportunity for some VFD manufacturer to make a VFD specificaly for single phase motors. I see no reason why a typical 3 phase VFD cannot be reprogramed to produce two phases 90° apart One phase for the start winding one for the Run. The start winding phase could have a different set of parameters to match the winding.
Am I out to lunch?

There ARE drives that work on some 1 phase motors. The problem is not in the ability to make a VFD, the problem is in the motor design. Single phase motors to not inherently spin on their own, they have to start spinning somehow, then they stay spinning. There are a multitude of ways to start them, most are too expensive and/or come with other consequences. The majority of manufacturers settle on Capacitor Start motors with a speed switch or voltage relay that switches out the capacitor when the motor gets to speed. That process exposes the VFD to damage from the capacitor charging current AND damage to the motor capacitor from the rapid rise rate of the PWM pulses. Plus f the motor speed is dropped to a point below which the Starting capacitor gets switched back in, the damage process is greatly accelerated. Motor choices without capacitor starting tend to produce too little torque for many applications, such as this one.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376