motor reversing

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oddjobfortwo
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motor reversing

Post by oddjobfortwo » Wed Jul 08, 2009 10:36 pm

hello all does anyone have a simple scematic for reversing for an a/c motor with a couple of limit switches? be gentle this is my first post thanks

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reloadron
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Re: motor reversing

Post by reloadron » Thu Jul 09, 2009 3:35 am

Hi and welcome aboard!

Much of what you are asking will depend on the motor in question. Would this be a single phase reversible AC motor or a poly-phase AC motor?

Ron

oddjobfortwo
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Re: motor reversing

Post by oddjobfortwo » Tue Jul 21, 2009 7:29 pm

im not sure but it has a neutral wire and the red and blacj wire you alternate for forward and reverse. i also need a stop button so it just doesent run continuaslly

mthornton
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Re: motor reversing

Post by mthornton » Tue Jul 21, 2009 9:02 pm

Assuming Mr. oddjobfortwo has a single-phase motor
Many 1-ph motors have separate run & starting windings. Reversing the direction of the motor is a matter of reversing the polarity of the start winding WRT the run winding(s). careful, because many 1-ph motors have 2 run-windings both brought out, allowing connection on either 240V or 120V. The start-winding is identifiable due to one winding end being connected to a centrifugal start-switch. Many start windings are 120V, and connect to the half-taps on the run windings.
You can go to your local tech college library, and look in an electric motor-book.
But, many 1-phase motors are not easily reversable at all. Some (shaded-pole) can only be reversed by swapping the stator ends WRT the end-bells

If Mr. oddjobfortwo has a three-phase motor, then you would likely be in an industrial setting, and you should get your electrician to show you how to reverse any 2 of the 3 phases to reverse direction.

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Bob Scott
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Re: motor reversing

Post by Bob Scott » Wed Jul 22, 2009 1:22 pm

I bought a 120V single phase surplus gearhead AC induction motor to make an actuator for rotating my C band sat dish. I had to make it reversible. There were two windings connected in parallel. I just had to reverse the AC power to one winding to make it run in reverse.
-=VA7KOR=- My solar system includes Pluto.

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dacflyer
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Re: motor reversing

Post by dacflyer » Wed Jul 22, 2009 2:40 pm

a pic of a data plate and wiring diagram would help a lit if you can provide that for us to see..

some motors are easy to reverse, they usually have 2 wired connected together, just reverse them..i see that a lot on condenser fan motors.

Dean Huster
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Re: motor reversing

Post by Dean Huster » Sat Jul 25, 2009 11:45 am

Be careful as it can be hard on the motor and the load to simply zap from forward to reverse and vice versa without a slow-down or full stop. Not to say that you can't do it -- after all, is a technique of motor braking, often using a plugging switch to handle the power removal when the motor speed has sufficiently slowed.

Dean
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

R.I.P.

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dacflyer
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Re: motor reversing

Post by dacflyer » Mon Jul 27, 2009 6:04 pm

i have played with some motors that were reversable, but they are supposed to come to a full stop before it will work,, if you switched them while running, they would continue to run the same direction, it is actually the start winding that would kick the motor the right connection..

rshayes
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Re: motor reversing

Post by rshayes » Sun Aug 09, 2009 6:13 am

Motors that are designed as capacitor run motors (as opposed to capacitor start motors) often have two identical windings that are desigend to be excited 90 degrees ot of phase. One winding is connected directly to the power source and the other winding is fed through a series capacitor. Often only three leads are brought out of the motor. One end of each winding is connected to a common lead. The other ends of the windings are brought out separately. The phase shifting capacitor is connected between these leads. If power is supplied directly to one winding, the phase shifting capacitor drives the other winding and produces torque in one direction. Moving the power connection to the other winding reverses the motor. This is quite convenient, sinces it allows a single SPST center off toggle switch to both turn the motor off and on and also control its direction.

As far as your original question is concerned:

Limit switches usually only operate when a limit has been reached. They are arranged to stop motor operation in one direction but allow the motor to be reversed to allow travel away from the limit switch. Relays or logic can be used to remember the direction of motor operation and limit switches can be used to cause the relay or logic to reverse the motor direction.

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