Simple AC Motor Question

[kirscp]

Hello,

Simple question .. I have a 115V 1hp AC motor, which I'll be using to power a ball mill (a big rock tumbler for refining powdered chemicals). It's a used motor, so there are no wiring diagrams.

There are three wire connections .. my assumption is the one would be direct connect to the ac .. and the other two are for a switch to be placed inbetween. If I connect them both directly, the motor would be always on when plugged in. Is that correct? Or how should I wire to run it directly?


Thanks in advance!!

Here is a pic

**broken link removed**

The red and yellow are in the rear posts of 5 & 2

 

[Klaus]

Looking at your picture I would assume you have a single phase induction motor there. These have a start and a run winding. Sometimes there is a capacitor as well, I assume there was none with your motor?

The black part where the wires connect to would be the centrifugal switch that disconnects the start winding once the motor had attained speed.

So, you have a common to both windings and one end of the start and the run winding coming out of the motor.
You have to figure out how the centrifugal switch contacts work to find out where to connect the motor to the mains. An on/off switch would be wired as a double pole switch to the mains supply.

If you want to find out which winding is the start winding, its the one with the higher resistance.

Klaus

 

[kirscp]

Alright,

I hooked my AC up to the top two and the motor attempts to run, but will not start unless I give it a spin, then it runs at speed.

It was a motor from a treadmill, if that helps any.

Would there be a way to power the motor up without having to give the pulley a spin? I'm thinking that because it was off a treadmill it needs that first help starting it, but I could be wrong.

 

[John Sorensen]

Just out of curiosity, when you give it a spin, does it continue to spin in whatever direction you start it?

j.

 

[kirscp]

I haven't tried to spin it the other way .. YET .. I'll do that and let you know.

The other thing .. the motor has been sitting for over 10 years and not been used. Could it just be just dust and what not causing enough friction to keep it from starting?

Again,

Thanks for all the information guys. Been a great help. (Didn't think the motor would be the tough part of my build) :roll:

 

[kirscp]

Double Post

 

[RGBrainbow]

Hi,
normally a single phase AC motor looks like this:

                                   .
                                   |
                                   |
                                   |
                                   |
                                   |
                                   '
                      o------------o--------------------o------o
                      |                                 |
                      |    centrifugal switch           |
                      |                              || |
                      |         _--o---------------o-||-o
                      o        o                     ||
                      |        |
                      C|       C|                            mains AC
         run winding  C|       C| start winding
                      C|       C|
                      |        |
                      o        o
                      |        |
                      |        |
                      o--------o---o---------------------------o


                                   .
                                   |
                   inside motor    |   outside motor
                                   |
                                   |
                                   '
created by Andy´s ASCII-Circuit v1.24.140803 Beta [url]www.tech-chat.de[/url]

How to identify the windings:
You can measure 3 different resistance values of the windings:
- high: start winding ---- run winding
- middle: common ---- start winding
- low: common ---- run winding


The capacitor is used to create a phase shift between run winding and start winding what causes the motor to start always in the same direction. If no capacitor is used the motor can be started by spinning it in any direction.
The value of the capacitor is ~7µF/kW motor power.

If the motor has not been used for 10 years have a look at the bearings. They might be dirty and/or rusty and should be changed.
Also have a look at the centrifugal switch. If it's not working correctly the start winding will not be switched off and might be overheated after a while.
When starting a single phase AC motor has low torque, so it might be usefull to start it with no or low mechanical load.

hth
regards
joachim

 

[RGBrainbow]

oops
sorry for double posting

 

[kirscp]

Just out of curiosity, when you give it a spin, does it continue to spin in whatever direction you start it?

j.

It will run either way I spin it. If I'm able to get something apart, I can figure out how it works, but this motor is welded togeter.

As far as the low/medium/high I'm guessing the motor is now attempting to run in high and not enough torque to start?

 

[Exo]

That probably means it's a 3-phase engine. Running it on 2 phases doesn't give it enough power to start (unless you help it)...

 

[Klaus]

That probably means it's a 3-phase engine. Running it on 2 phases doesn't give it enough power to start (unless you help it)...

He's trying to run it on single phase - it would rule out your 3 phase theory.

I think, from the hand spinning report, either the start winding is not connected ( dirty/ faulty centrifugal switch), it is incorrectly or not at all connected externally or it is burnt out.

And, while many single phase induction motors have a capacitor to increase the starting torque, they do NOT have to have one to start, if the motor is designed for capacitorless starting.

Klaus

 

[dano]

maybe if you could post the resistance readings : red-black, red-yellow, yellow-black we might be able to figure which are the start and run windings. (this assumes there is no capacitor)

Dan

 

[panic mode]

and what about nameplate?

 

[kirscp]

maybe if you could post the resistance readings : red-black, red-yellow, yellow-black we might be able to figure which are the start and run windings. (this assumes there is no capacitor)

Dan

Readings at 20 OHMS

Red-Black - 3.4
Yellow-Black - 4.9
Yellow-Red - 1.6

Red to Black will not start it, but after a few seconds it starts smoking .. Looking closer there are thinner copper wiring that is melting the plastic. I assume Red-Black is for starting and after starting it should switch to Black-Yellow .. However NOW Black-Yellow trips my breaker (didn't happen before). Could the running combo be the red-yellow though they are on the same side?

This motor is sure a pain in the ass. I remember why I don't like treadmills!! :lol:

Nametag:
**broken link removed**

 

[kirscp]

scratch the yellow-red for running. Now those also start it, but start smoking after running for 10 seconds.

When the black-yellow worked it never smoked. I need to figure why it's now shorting out ..

 

[kirscp]

I took the switch apart and found out how the switch works .. however now the thing copper switch is fried, so I'll have to figure out how to fix that .. or I'll just have to make my own switch.

Here is a picture of the switch -

**broken link removed**


The copper piece that is circled in red is what burnt off. When the motor got up to speed the force of the motor pulled down (green arrow) and allowed the connection between the top two.

Basically it needed to be oiled also .. as i had to spin start the motor no matter what series I connected them.

If I would have known it was that easy to take it apart I would have done that from the start

Hopefully I can get it now ..


EDIT:

Red - Yellow/Black for start

Seems either Red - Yellow or Red - Black for run.

 

[computeruser]

Is it possible this motor is DC voltage? Generally all treadmill motors (being variable speed) are DC. Three leads out is odd - common lead to 1/2 of field and armature?