Simple question, (not for me) about reversing Single phase 220V motor - Page 1
Forum section: electronics / projects

author: federico
author_rank: Contributor
timestamp: September 23, 2020, 02:51:50 pm
content: Hi everyone.I am converting a cheap pillar drill into a "threader", I want to put a switch to reverse the direction of the spindle.On another drill some time ago i had no problems, there was also the label with which wires to reverse.But there is no ticket on this one, and there are only 2 threads:Motor input voltage: AC 220Vwire 1: phase ,wire 2: neutral(third ground wire)I tried to reverse phase and neutral, but it always goes in the same direction, (there is a capacitor)I assume that reversing the capacitor does not change anything,how can I change the wiring?I attach photos:Thanks everyone in advance for your help.

author: Ian.M
author_rank: Super Contributor
timestamp: September 23, 2020, 03:43:59 pm
content: You'd have to tear down the motor to find both ends of either the main or start windings and reverse one of them.

author: federico
author_rank: Contributor
timestamp: September 23, 2020, 04:40:22 pm
content: Thanks for the reply.I took the motor apart, do you intend to cut those little white cords and open the white sheaths to find out where the little copper wires go?

author: IanB
author_rank: Super Contributor
timestamp: September 23, 2020, 04:55:35 pm
content: If the motor does not have different colored wires inside the case with an instruction plate about which wires to swap, then the motor is for practical purposes not reversible.Maybe if you are fully able to strip down motors and reassemble them neatly with all the required tapes, bindings and connections as it looks in the photo, then you might be able to reverse it. Otherwise, best not to try.

author: Ian.M
author_rank: Super Contributor
timestamp: September 23, 2020, 05:28:25 pm
content: Yes, what t'other Ian said. Unless you've got the skills and materials to do a competent job of separating the common end of the main and auxiliary windings, (it appears to be a PSC motor), bring out an extra wire for the latter and restore all insulation and bindings to 'factory' condition its best not messed with. If you've got a local motor rewind shop, you *may* be able to get them to quote on it. N.B you also need to check if its cooling fan is reversible. Most axial fans and flat radial blade centrifugal fans are, but other types of centrifugal fan generally aren't.

author: james_s
author_rank: Super Contributor
timestamp: September 23, 2020, 08:34:22 pm
content: It's probably possible to reverse it, just depends on how much effort you want to invest. You'll need to cut into that bundle of junctions, I'm betting the free ends of both windings will all be in there.If you want to really do it right, find a small 3 phase motor and use a VFD. That's how the drill presses converted to threading rigs at my friend's shop are set up. You step on a pedal to make it go forward, release the pedal and it reverses. In addition the inverter gets you variable speed from a crawl to over 100%, soft start and other features.

author: WattsThat
author_rank: Frequent Contributor
timestamp: September 24, 2020, 01:57:08 am
content: QuoteThose “little white cords” are nylon lacing cord to keep the windings held tightly together so they don’t vibrate at the mains frequency, rub the insulation away and fail shorted. Cut them off and eventually the motor will fall.A small three phase motor and VFD is by far a better solution for tapping since you can ramp the speed and control direction.You’ll just break taps with direct drive since you cannot control the torque.

author: federico
author_rank: Contributor
timestamp: September 24, 2020, 06:50:34 am
content: Thanks everyone for the answersianB, IanM: yes, I have the tools and i am quite experienced, I don't think I have a problem doing that, the fan is flat, no problem.I am undecided whether to do it or not .. if by restoring everything back to work, I might as well try it.james_s: I already have two poor sewing machine pedals, in case of failure I wanted to order a motor with reversible threads and use the two pedals which only act as a button, (without sensitivity), the 3 phase with VFD would be cool, but I'm trying to do it economically and as soon as possible, (I have to thread 600 holes between tomorrow and after.WattsThat: Okay, so I should modify the wires and put them back with their sheaths in that exact position? if I can't, it will never work again.(I thought they were just for holding the cables in place)Ok, now I don't know whether to do it or not ..

author: Ian.M
author_rank: Super Contributor
timestamp: September 24, 2020, 07:41:56 am
content: It looks like the wiring joints are in fibreglass sleeving, which could probably be slipped aside without any need to cut it if there was enough slack in the wires and it wasn't laced down. *IF* the lacing securing the joints in their sleeving is tied off separately to the lacing securing the winding, and I had appropriate lacing cord in stock, I'd be inclined to dig into it further. OTOH if the lacing appears to be all one piece, I'd *NOPE* right out of there, as re-lacing it properly to re-secure the coils would be more hassle than I'd care for.

author: james_s
author_rank: Super Contributor
timestamp: September 24, 2020, 05:57:48 pm
content: Quote from: federico on September 24, 2020, 06:50:34 amThe wires don't have to be put back in the exact position but you should try to keep everything tidy. Avoid disturbing the coils themselves, I don't think you will need to mess with those. I don't think they will move around much either, usually they are soaked in some resin to stick everything together. It looks like a cheap motor so if you do damage it there is not a huge loss. If you want to modify it just try to disturb the insides as little as possible while getting to the end of the wires. I don't think you will be very happy with the performance though, a VFD is really much better.

author: Ian.M
author_rank: Super Contributor
timestamp: September 24, 2020, 06:13:21 pm
content: What you *REALLY* need is a Tapmatic auto-reversing tapping head.

author: james_s
author_rank: Super Contributor
timestamp: September 24, 2020, 06:31:16 pm
content: Those Tapmatic things are cool, although my friend's shop stopped using the ones they had when VFDs became cheap. A 3 phase motor on a VFD does anything a Tapmatic can do and more.

author: federico
author_rank: Contributor
timestamp: September 27, 2020, 11:49:44 am
content: Hello everyone, sorry for the delay in replying, I did it!I disassembled the wire bundle, the neutral goes to the main coil and the phase goes to the two wires of the "secondary" or starter coil, as you call it.The capacitor receives the phase and sends it to one of the two wires of the secondary coil, then the output of the capacitor, connected to wire 1 secondary coil goes in one direction, to wire two secondary coil goes in the other.I hope I am not confused, I made the change days ago, I made a horrible little drawing,I hope it is clear.(I cut, welded, modified the length of the cables, and tied the cables just to keep them from moving, without putting everything back exactly in the original position, but thrown them at random, and doing the job without particular attention, I used a normal shrinking sheath , the motor works great in both directions, so don't worry too much, only caution, do not scratch / damage the copper wires of the winding, I have soldered and cut on the original soldering of the wires and I have cut the wires after soldering, not I "handled" the copper wires of the windings)I ordered on amazon 2 sewing machine pedals, I spent 8 €,When I press pedal 1, the phase reaches auxiliary wire 1, when I press pedal 2, the phase reaches auxiliary wire 2.the pedals have 3 poles, com, normally open, and normally closed,The phase arrives at the com of pedal 1, it leaves the normally closed of pedal 1 entering the com of pedal 2, so when pedal 1 is pressed, the phase goes to the motor and is excluded by pedal 2.if both pedals are accidentally pressed, pedal 2 is excluded and the motor proceeds in the normal running direction, and phase from both pedals will never arrive at the same time.The start was obviously 100% immediate, impossible to fillet without destroying the taps, so I bought a 220V voltage regulator (€ 9) to regulate the speed.I also added a switch to disconnect the phase to the drill, so we avoid accidental switching on the pedals.The only flaw is that the speed regulator works, but if you adjust it to make it run slowly, the engine has very little power, so you have to adjust it a little faster than you need and dose the pressure time carefully, but I like it this way it also works as a soft starter as well.It's not the best, but for 17 € I'd say it's great.I have a lot of stepper motors that I replaced on my 4 axis CNC some time ago, later I build a well done bench threader.Thank you all for the support !I uploaded a video(for indexing)How to reverse direction motor monophase, economical column drill.

author: Ian.M
author_rank: Super Contributor
timestamp: September 27, 2020, 02:43:07 pm
content: I don't see *HOW* that wiring diagram (IMG_20200927_123523) could work.How does power get to the other end of the main winding? How is the auxiliary winding reversed?Also I suspect that unless you've put quite a bit of thought into interlocks, with your extra supply switch on, if anything pushed both pedals at once (e.g. something fell on them) *BAD* things would happen, maybe if you are lucky just the breaker tripping but if you are unlucky the motor could catch on fire.

author: federico
author_rank: Contributor
timestamp: September 27, 2020, 06:55:05 pm
content: I do not invert the wires, the wiring remains the same, but the phase that was originally connected to one of the two wires of the auxiliary, I bypassed it in the pedals, and when I press pedal 1, the phase reaches the auxiliary wire 1, when I press the second pedal phase is given to the second auxiliary cable, and the direction is reversed.If you press the two pedals at the same time it would bring the phase to both ends of the capacitor at the same time, you say it explodes?I found the solution, it was very simple,the pedals have 3 poles, normally open, and normally closed, I simply connected the phase of pedal 2 to the normally closed of pedal 1, so when you press pedal 1, the phase goes to the motor and it is excluded from pedal 2.if both pedals are accidentally pressed, pedal 2 is excluded and the motor proceeds in the normal running direction, and phase from both pedals will never arrive.Great, luckily you wrote to me, I hadn't thought about it, I would have made the phase reach both sides of the capacitor...I redid the design, now I edit the previous post.

author: Ian.M
author_rank: Super Contributor
timestamp: September 27, 2020, 07:03:50 pm
content: Ah. that's starting to become clearer. From your original diagram all I had understood was this, which obviously cant work because the main winding doesn't get Phase and the Aux winding doesn't get Neutral switched from one end to the other.I'll follow up when I've had a chance to think about your description and maybe plot it out.

author: Ian.M
author_rank: Super Contributor
timestamp: September 27, 2020, 07:55:07 pm
content: So in one direction, you have the motor wired normally. In the other direction you are using the Main winding in place of Aux and the Aux winding as Main. See attached diagram. That's permissible if the two windings are identical, (i.e. equal wire gauge and equal resistance), but can result in a burnt out motor if you do it with an ordinary motor's thinner wire higher resistance Aux winding as its getting too much voltage with no series capacitor. Also it tends to loose torque when reversed that way.