Electric Motors - which is what?


Old 06-16-10, 11:00 PM
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Join Date: Jun 2010
Location: australia
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Electric Motors - which is what?

Moderator: sorry if this is the wrong area - I couldn't find anything for 'electric motors' - please move it where it belongs if this is wrong.

I need to replace an electric motor in a concrete mixer and I need some information/advice so's I can do that.

The mixer is a very old type with a very old electric motor and the motor slows and stops nowadays when it gets hot.

I've actually got two mixers like that, same type, same type of motors. But the second one the motor seems okay so far.

I've got a new motor donated by a friend but it is not quite the same as the old motors.

The old motor has a 'can' on the side which I'm told helps it in starting up. The new motor doesn't have such a can but it is wired up to a plug as though you just plug it right in. And it only has two wires into the plug, too, which I wonder about.

The new motor has a plate on the side with all kinds of info. Unfortunately the old ones don't have any such plate after all these years.

So the question is: can I replace an old motor with this new one? How should I wire it? Are there any dangers?

I did read a bit on Google but found it quite daunting, all that technical stuff about motors, I soon got lost. Couldn't learn enough to solve my problem myself.

However I was caught by what it said about some induction motors drawing 9 or 10 times the full load current when started DOL ( a techie term I just learned ) (Induction motor - Wikipedia, the free encyclopedia)
which I suppose is what is happening with a motor wired direct to the plug without any 'can' on the side.

And 9 or 10 times full load current sounds like enough to blow house fuses to me (single phase australia 240v ).

so I'm after help. anyone?

pictures of the motors at: http://picasaweb.google.com/abrogard...eat=directlink


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Old 06-17-10, 04:48 AM
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Just one question to get things rolling. The old motor, you say you just plug it in and it runs (most of the time?). The replacement motor you have is a 240 volt motor. Do you have ready access to 240 volts where you use this mixer? Most likely not. Just curious about the voltage requirements of the old motor.
Old 06-17-10, 04:53 AM
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Yes, I just plug it in and it always works. But on a hot day after a couple or four loads - maybe an hour's working - it will start to just cut out and I figure that's from overheating?

I leave it a while and come back to it and it always starts again.

So I've gotten into the habit of switching it off while I barrow the concrete away and pour it.

I'm using it close to the house, next job is to pour a slab for a 6m x 9m shed. That's why the two mixers, so's we can produce more concrete. So there's 240v to hand all the time. Single phase, as I say.
Old 06-17-10, 04:56 AM
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Are the RPM's of your old and new motors the same? Electric motors are available in different RPM's. Put a mark on the shaft of your new and old (running) motor and turn them on. You should be able to see if they spin about the same speed or if one motor is turning twice as fast.

Are the motor output shafts the same diameter? If not you will have to have to get a new pulley or have your pulley machined to fit the new motor.

Do you know the horsepower of your old/existing motors? I would not go to too much effort until you know the new motor has enough power to do the job.
Old 06-17-10, 05:19 AM
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Location: australia
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No, I don't know about the RPM's as yet. No drama, I can figure all that out.

The point of these questions is they'll set me up for swapping the motor when I do I have one of the correct horse power and rpm's (assuming this one doesn't).

I guess there's a fair amount of variation allowed in mixer speeds. There's a belt on the side of the thing which I can change to help with adjusting speeds, too.

These old mixers have, I'm told, traditionally been run with motors cannibalised from washing machines...

I'm hoping to discover something about the function of that 'can' on the side of the other motors and what's it signify that this one (and many other motors) doesn't have one and can I/should I start this motor directly from the power source... stuff like that...

p.s. There's something I've never seen before happening here. I'm getting email notification of posts to this thread which are from Facebook, apparently. My browser throws up a danger message claiming to have detected malware. This forum, this site, hasn't been infected with something has it? I got my first notification okay, but since then......

Here's the message I get:

Warning: Visiting this site may harm your computer!
The website at home-sun-tube.net appears to host malware – software that can hurt your computer or otherwise operate without your consent. Just visiting a site that hosts malware can infect your computer.
For detailed information about the problems with this site, visit the Google Safe Browsing diagnostic page for home-sun-tube.net.
Learn more about how to protect yourself from harmful software online.
I understand that visiting this site may harm my computer.

How about that? Anyone seen that before?

I've put screengrabs of what I got up on the web at Picasa if you want to look:

Last edited by abrogard; 06-17-10 at 05:36 AM. Reason: provide link to picasa pics of malware warning
Old 06-17-10, 06:17 AM
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The can on the side is a starting capacitor. It aids in handling the starting load until the motor gets up to full speed.
Old 06-17-10, 06:21 AM
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It sounds like you are getting some unrelated spam. I've never had virus problems from surfing this board. I would not even open an E-mail that looks suspicious.


Good, it sounds like you can get whatever you need for RPM and HP. You already have a very small pulley on the motor and it looks as large as you can go on the mixer so you are about out of reduction that you can do with the belt.

If you can get whatever motor then I would go for a capacitor start. It is better at starting with a load on the motor (if your mixer does not turn freely or already has some material in it). You could get away with a non-capacitor motor but you would have to make sure the drum is empty and let it get up to speed before you put a load on it.

This link has a pretty clear description of the difference between a capacitor and non-capacitor (split phase) start motor.
Old 06-17-10, 08:15 AM
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Pretty much as long as the motor have the right frame (how it mounts to your mixer) RPM, HP, voltage, and shaft diameter for your pulley you should be good to go. If you can tank to a motor shop they should be able to get one that will work for ya!
Old 06-17-10, 05:01 PM
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Join Date: Jun 2010
Location: australia
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Ah.... no weird virus-type reactions this time...

That was an excellent link, thank you.

I'd say it is obviously preferable to have a capacitor start motor.

The link doesn't say if my (or any other) motor can be converted to a capacitor start? Or have I got to go looking for one that is designed as 'capacitor start'?

Motor shop? I guess we must have one somewhere in the local town but I don't know where it is, I've never seen it, I'll start searching.

What I'm doing currently is just looking at second hand motors from dealers and a couple on offer from friends....

It would be good information really to consult with a 'motor shop' and hear what they have to say about what I need and the cost for getting it new. I'll do it if I can find such a shop.

Or maybe I can find a company on the internet.....

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