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Total beginner... so I don't know if what I want to do is easy or hard!

Nafnlaus

Sep 14, 2015
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Hi everyone. My electronics experience doesn't extend much beyond an electronics kit as a child and what I learned in college physics and computer design courses, so I'm a complete beginner here - go easy on me :)

I have an old table saw motor (minus the table and all saw components) that I'd like to repurpose in another project - but for the other project I'll need to be able to reverse the motor - something that I don't know whether it's possible to do. I already have a three position double-throw lever on hand that I could use for the purpose, if I could figure out how to rewire it. But the question obviously becomes, A) is it even possible and B) if so then how? And obviously that depends on the circumstances - and I don't know if those circumstances are obvious to a person with experience or if there's something that will take lots of digging. So, here's what I know so far!

First off, a few pictures. The main motor body info plate:
https://www.flickr.com/photos/[email protected]/21396415926/in/dateposted/

Attached to the motor is a large capacitor and a small wiring box:
https://www.flickr.com/photos/[email protected]/21234570060/in/dateposted/

The wiring inside the box is relatively simple:
https://www.flickr.com/photos/[email protected]/21235687439/in/dateposted/

I made up a wiring diagram, as best I could:

https://www.flickr.com/photos/[email protected]/20800488814/in/dateposted/

(I don't know if the writing (voltages, symbols, etc) on those white screw boxes is actually meaningful or if it's just something that happened to be written on mass-produced parts that they used.)

The challenge is, of course, the white wires disappear into the motor, where I don't know what they do (I could probably open up the motor, although it'd be a bit of work); and the wiring leading into this box isn't straight from the mains, rather from a controller box. And it unfortunately isn't so simple:

https://www.flickr.com/photos/[email protected]/21234777228/in/dateposted/
https://www.flickr.com/photos/[email protected]/20801523443/in/dateposted/

I haven't attempted to diagram that yet, it'd take a long time and would require significant disassembly - if I can do it at all without damaging it.

https://www.flickr.com/photos/[email protected]/21234794928/in/dateposted/
https://www.flickr.com/photos/[email protected]/21235711239/in/dateposted/
https://www.flickr.com/photos/[email protected]/21431054621/in/dateposted/

So the basic question is... is there something that stands out here as a case of "Oh yeah, that's easy, I'm 90+% sure that to reverse directions you just need to reverse wires X and Y", or is it a case of "I have no clue, you have to have a full understanding of the circuitry as a whole to know, you can't even guess without that"?

Thanks, and thanks for putting up with my beginner-ness :)

(Too bad it's not a motor that takes three phase power - if it were I could just simply reverse two of the three phases and it would probably just reverse, right? :) )
 

Tha fios agaibh

Aug 11, 2014
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Changing rotation is accomplished by swapping the leads of the start winding. This is the motor winding with the smaller size wires on the stator that hooks to the start capacitor. I don't see the leads are in the motor box. You may have to crack the case to get access to them. (Not easy)
Another way to change the wise of rotation, is to physically turn the way the armature goes into the stator housing. Sometimes it can't be done because of where the wires rout from.
Good luck.
John.
 

Nafnlaus

Sep 14, 2015
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I'll see if I can crack the case and see which wires lead to the start winding - thanks a lot :)
 

CDRIVE

Hauling 10' pipe on a Trek Shift3
May 8, 2012
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Changing rotation is accomplished by swapping the leads of the start winding. John.

That was my initial thought until I saw the photos of the controller associated with this motor. There's not much one can do with a 1PH induction motor besides the ability to reverse it on some models. So it begs the question what does the controller do?

Chris
 

Minder

Apr 24, 2015
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Usually motors fitted to the likes of a table saw are only expected to run in one direction so often the winding pair are connected internally, you can swap either the run or the start winding WRT the other.
usually both ends of each winding is required with the exception of motors where the windings are identical, which it would not usually be in this case.
Due to the apparent electronics, the technology of the motor may not be Induction motor but universal etc?
That Shurter device is a circuit breaker.
M.
 
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Martaine2005

May 12, 2015
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So it begs the question what does the controller do?
Hi Chris,
That little box of tricks on an Elektra Beckum table saw is normally a soft start, speed control and sometimes a break too.

Martin
 

CDRIVE

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Due to the apparent electronics, the technology of the motor may not be Induction motor but universal etc?
That Shurter device is a circuit breaker.
M.
Hi Chris,
That little box of tricks on an Elektra Beckum table saw is normally a soft start, speed control and sometimes a break too.

Martin

If it's a soft start then it's definitely not a cap start induction motor. It's probably a Universal motor as Minder suggests.

Chris
 

Martaine2005

May 12, 2015
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I think most tools are universal motors. Could be wrong of course.
Also most up to date tools (bench tools) have the green and red stop start safety switches too.
I know all mine do have them.

Martin
 

Minder

Apr 24, 2015
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The capacitor sort of indicates a split phase induction motor, VFD control of 1ph motors is not that successful, but if it is only soft start and used to get it up to max rpm without any speed control, then it could be split phase.
The absence of brushes would confirm it.
M..
 

Tha fios agaibh

Aug 11, 2014
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I agree with Minder. Universal motors are more often used in Circular saws, than table saws.
Where are all you European guys to way in on this?
Nafnlaus: Why the heck do you want to run it backwards?
 

Minder

Apr 24, 2015
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The 50Hz 2800rpm sort of indicates a 4 pole (induction) motor, which for a saw is a little unusual as saws usually run at high rpm, mine is a 2 pole 3480 rpm on 60Hz.
M.
 

Martaine2005

May 12, 2015
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Hey Minder,
Perhaps you could do a resource section on different motors.
You are obviously clued up with them.

Martin
 

Minder

Apr 24, 2015
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I could dig up some references, there are basically 3 kinds of motor found in the home, 1ph (split phase) induction motor, Universal (AC/DC brushed) motor, and dc P.M. brushed in battery operated portable tools.
The universal motor being a series motor essentially operates in a runaway condition, mainly friction and windage (fan) are the deciding factor for max. rpm.
e.g. if you unload a vacuum (series motor) by covering the pipe you hear it accelerate to higher rpm.
Older automobiles use a DC series motor for the starter, so this should not really be ran on a bench with no load due to overspeeding.
M.
 

Martaine2005

May 12, 2015
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I could dig up some references, there are basically 3 kinds of motor found in the home, 1ph (split phase) induction motor, Universal (AC/DC brushed) motor, and dc P.M. brushed in battery operated portable tools.
I really think you should do a resource section on different motors.
But no abbr's. Just a clean cut resource.
You are very knowledgable.
Dare I say it? I love your math and physics too.
Does it always have to be facetious?

Martin
 

Minder

Apr 24, 2015
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Back when I was in the process of taking my electrical/electronic qualifications, a popular 1st year mid term exam question was if you have a shunt wound DC motor and the field winding supply is disconnected while the motor is running:
1/ Does it slowly revolve to a stop?.
2/ Speed up out of control?.
3/ Remain running without change?
M.;)
 

CDRIVE

Hauling 10' pipe on a Trek Shift3
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Back when I was in the process of taking my electrical/electronic qualifications, a popular 1st year mid term exam question was if you have a shunt wound DC motor and the field winding supply is disconnected while the motor is running:
1/ Does it slowly revolve to a stop?.
2/ Speed up out of control?.
3/ Remain running without change?
M.;)

Under load I believe it would be 1. My guess is that if it's unloaded it may keep running (3) do to residual magnetism in the field poles.

Chris
 
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