Wiring for AC motor. - Page 1
Forum section: electronics / beginners

author: primegaps
author_rank: Contributor
timestamp: June 19, 2018, 11:53:57 pm
content: Hello. I found this AC motor but i do not understand the wiring.I took of the panel which gives me access to some wires, here are some pictures.What are each of the set of three wires? What about those other two?I figured I would just have to supply 120AC, but its got quite a few more wires than just the three i figured.In this first pic you can see a pair of grey green wires tucked away up above. I tried to pull those down, and the insulation cracked off. You can see this in the second picture.Here is a picture of the badge.Also it has a large can on the top of it. Is this a Starting Capacitor? Do I need to replace this?Thanks!

author: Yansi
author_rank: Super Contributor
timestamp: June 20, 2018, 12:14:05 am
content: I dare you not to run the motor at all, before doing a bit of safety inspection first. The insulation on the wires is falling apart and the wire insulation inside might be compromised too.So start by dismantling the motor and checking what the inside looks like. Then replace carefully the leads coming out of it. Check insulation resistance with a megger.Then if all that is done, first you need to figure out the type of the machine, so you will be able to wire it accordingly: From the photos it seems it is plain simple induction motor, single phase 115/230V with a run capacitor (that is the big can on the top. The cap should be checked too and preferably replaced).The wiring is not clear to me from the photos, would need to measure it with ohmmeter first, to figure what is connected to what. Could you please do that first? Measure all the windings there and draw a picture of what was found. Then it will be much clearer how it is supposed to be connected.//EDIT: Seems only the wires from the run cap are falling apart. Still, should be changed (probably together with the old cap) without a thought.

author: Yansi
author_rank: Super Contributor
timestamp: June 20, 2018, 12:31:35 am
content: I have found you a bit of inspiration, how it may be wired, which corresponds well with your motor. It may after all be a start capacitor type motor - it will likely have a switch in it, that disconnects the cap after getting it up to speed.See here:https://www.practicalmachinist.com/vb/south-bend-lathes/help-please-wiring-switch-motor-257832/index2.htmlAfter all, this image from that page corresponds quite well I guess:As the motor can run both 230 and 115V, there are two windings connected in parallel for 115V operation, or in series for 230V.Then there is the start winding, in series with the start cap and probably a centrifugal switch. (likely the blue wires, should measure dead short across them when the motor is stand still).There are two triplets of wires twisted together. One of the triplet is your line, the other neutral. (your motor being connected for 115V operation).

author: Yansi
author_rank: Super Contributor
timestamp: June 20, 2018, 12:35:43 am
content: If you could make sharp good lit photos of the terminal box of the motor, I see there even description for the wires pressed into the plate. At least I can see "T3" for the white wire.Please do a more thorough photo or describe what color is what terminal noted on the plate.