View Full Version : reversing an AC motor

05-01-2016, 02:04 PM
motor is a 1/4 hp Eland Electric 110 1P motor that I want to reverse. I'm used to finding instructions inside the plate cover on whats what to reverse. There are two posts that are already connect to the lines and a screw visible as per photo. Any clue how to reverse this? I thought of just putting a variac on it and trying different combinations, but maybe its obvious to those of you who know these things

if you labelled the three poles 123 left to right in the photo, resistance 1-2 - 2 ohms, 2-3 2 ohms and 1-3 =0.2 ohms.

I'm thinking white should go from pole 3 to 1 to reverse it??

edit: on closer inspection 1 2 and 3 have embossed on on the board S S L. Based on that , Black should be switched from one S to the other, right? when I undid screw "1", the nut or whatever the screw went into fell off so now its take the motor apart time. sigh.


http://i20.photobucket.com/albums/b201/michael0100/IMG_00001508_zpskywwmikp.jpg (http://s20.photobucket.com/user/michael0100/media/IMG_00001508_zpskywwmikp.jpg.html)

05-01-2016, 02:36 PM
maybe google with info from your motor (maker/model) and you'll find something. the motor I just bought brand new didn't have that info on it either, but I was able to find the wiring diagram on the innertubes.

05-01-2016, 03:15 PM
I have a 5 gal ice cream freezer that is powered by a motor and gearbox. When we put it together a few years ago, the motor turned the wrong direction and couldn't be reversed with wiring. I removed the rotor and installed it in the stator in the opposite direction. It did require some slight modifications to the case but it worked like a charm.

05-01-2016, 03:20 PM
Don't ask me how, but I think the starting circuit needs to be re-configured. Someone will be along shortly to tell us how. Probably is available on youtube. Good luck.


05-01-2016, 03:24 PM
Does the motor have a capacitor? If so, one end should be connected to the start/run winding. Those connections need to be reversed.

The Artful Bodger
05-01-2016, 04:26 PM
.........deleted by me..............(don't know what I am talking about)

05-01-2016, 04:32 PM
.........deleted by me..............(don't know what I am talking about)

haha, you and me both.

no cap. took it apart, its got the centrifugal starter, so whats that make it, a split phase? Have to get cleaned up for a family thing.....pics later

05-01-2016, 05:10 PM
You need to reverse the polarity of the start winding, one end of this will be connected to the centrifugal switch, the trick is finding the other end and swapping the connections over, it may be connected to the back of one of the bolts on the bakelite connection plate. when you find it, check continuity with a multimeter so you know you have the right connection, then put the one that was on the connection to the cent switch, and the one that was on the cent switch to the connection, and the motor will reverse. You may have to lengthen some of the wires if this motor was not designed to be reversed, some aren't.

05-01-2016, 05:31 PM
The frustrating part is yesterday I thought, well I get it running like this because its there (lathe drive unit) until I feed a good deal on a DC motor which is really what I want.......I'm half a mind to bin it and go find a DC motor. with it opened up it will be hopefully easy to identify the leads to the two windings. Thanks all for the help.

J Tiers
05-02-2016, 11:32 AM
That motor, like most any, is actually reversible, BUT it was not INTENDED to be reversible. So they didn't give you the connections, and you would have to go dig for them inside the motor.

That may be beyond your tolerance for electric fiddling, and, frankly, the better thing to do is get a motor that CAN BE reversed easily. Unless that one is something special.

05-02-2016, 01:16 PM
If the start and run winding's are identical it is very easy to switch as the cap is switched to either one or the other winding, often seen on motors of this size, Same as garage door motors etc.
If so just needs a SPDT toggle with centre off.
It appears you have two identical readings so this is most likely the config (PSC motor).
Can't upload a PDF here otherwise I could post it.
If you think you need it PM me.

05-06-2016, 02:27 PM
so it turns out it was super easy to reveres-----just reverse the two wire connections in the photo. However it required taking it apart to see that; they were the start coil, the run coil was attached to the same two pins but from behind.

Got it running, but end of day decided to scrap it. It was plain bearings which were loose and the seals were completely gone. One of the run leads was badly frayed. I decided it wasn't worth it so I pulled another 1/4 hp one from "inventory" and the lathe is running!

thanks all for the help

J Tiers
05-06-2016, 03:16 PM
so it turns out it was super easy to reveres-----just reverse the two wire connections in the photo. However it required taking it apart to see that; they were the start coil, the run coil was attached to the same two pins but from behind.


thanks all for the help

In your picture, the wires seem to clearly be the incoming AC cord wires..... reversing those would not do ANYTHING.

Is that not the SO cord I see exiting through a cord clamp?

Are we all looking at the same picture? I see only 2 wires, and they appear to go to a cord and out of the motor.....

05-06-2016, 05:08 PM
Normally on these simple PSC motors there are two windings alternately operating as start/run and main. the two windings have a common connection to which one side of the power is connected and the the other ends of each have a capacitor across them.
The other power line is switched between either end of each winding, depending on direction needed.
IOW three terminals.
The SPDT switch changes direction by alternating the direction.

05-06-2016, 05:27 PM
In your picture, the wires seem to clearly be the incoming AC cord wires..... reversing those would not do ANYTHING.

you are right, my apologies.....shakey memory between that pic and it being apart. Its fuzzy but I think one start lead is there, beyond a line, and the other might have been attached behind....anyway with it apart it was clear how to reverse them (start coil leads). I did learn how to reverse a SPM which is good, but its out of service now.

Max I think its a split phase motor, ie centrifugal switch not a capacitor motor.....but I also think you know a lot more about these than I so may be missing something. I

05-06-2016, 05:44 PM
If there is no capacitor, it may be a resistance split-phase induction motor, limited to about 1/3 HP.





J Tiers
05-06-2016, 07:01 PM
Yes, resistance-start.

A capacitor-start uses a relatively low resistance start winding, using the capacitor to advance the phase of the start winding. That produces a reasonable rotating field, and so torque that starts the motor.

A resistance-start motor uses a higher resistance start winding, which has the effect of swamping out some of the inductance, and so slightly advancing the phase of the start winding vs the run winding. Again, it produces a rotating field. The resistance is not nearly as effective as the capacitor in changing the phase, so it normally pulls more current and has less torque.

BOTH are actually "split-phase", as they have means for turning a single phase into two phases for starting.

Both a cap-start, and a PSC type will have a capacitor associated. The cap start uses a much larger capacitor, as a rule, normally in hundreds of microfarads, and usually an electrolytic. It also uses a start switch. It, and resistance-start induction motors, are "constant speed", varying no more then 5 to 10% from no load to full "breakdown torque".

The PSC has no start switch, and uses a smaller capacitor, usually no more than a few tens of microfarads, and often less than 10 uF for smaller motors. The PSC splits the phases" for both start and run. It has poor start torque, and poor speed regulation.

05-06-2016, 08:45 PM
thanks guys for the good education....I'm getting there :)