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Thread: Power feed buy new or repair?
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26th Sep 2019, 10:34 PM #31
Hi Simon,
In modern DC motors the field coils are replaced by powerful magnets. However your motor has two identically wound coils, somewhere there will be a link connecting the ends together. Probably hidden in an insulating sleeve somewhere.
02ef689ba9904952beba07c3e0383d12.jpg
There is another configuration that is sometimes seen, where one end of each of the field windings is attached to one of the brushes and power is fed into the other ends. Your motor is not of this type of construction !
If one or both of the windings has gone high resistance, you could rewind them yourself ! Not a too difficult task but one that would easily be doable with care. But we can tackle that if we need to. For now we need to find out.
As far as the armature not burning up, it will never have had the full mains (110 volts) applied to it. On average maybe less than a third in normal use.Best Regards:
Baron J.
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20th Oct 2019, 07:29 PM #32
Hi Simon,
Since you have not come back on this, I wondered if you have decided not to continue with a repair.Best Regards:
Baron J.
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20th Oct 2019, 08:19 PM #33Most Valued Member
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Hi Baron,
No it's still sitting on the bench waiting. I have in fact found an d disconnected the wires that connect one side of the field windings to the other.
However, I have also recently been scraping the shaper ram, finishing the VFD installation on the mill and now just recently about to complete a quick adjust quill feed handle for the same mill.
In between working 60 hours a week....
It's been on my mind. I will tackle it again probably next week.
I really have appreciated your help with this. It probably would have been in the bin long ago if not for your help.
I'm slowly contemplating and preparing myself mentally to rewind the field by hand. It's got a lot of crud and glue which I need to remove in order to unwind and count the number of windings.
Give me a week!
Simon
Sent from my SM-G970F using TapatalkGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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21st Oct 2019, 05:10 AM #34
Hi Simon,
I've been watching your thread on scraping your shaper and quietly sympathising ! Having spent quite a lot of time myself learning to scrape little bits in comparison to what you have done.
Being retired there is no panic to do this and do that, so I do as much as I feel at any one time ! Some days its hard work, others fly by with not enough time to complete anything. I try and read the forum daily, though I don't always manage it. I'm here when ever you are ready to continue with this project.
As far as counting the windings is concerned, I would just cut across the bundle, slit the insulation to free the wires then count them and multiply by the length. The other is just to weigh them and measure the wire gauge. Either method will work, and its not that critical as long as both windings are the same.
Do both sides measure the same resistance ?
Anyway shout when readyBest Regards:
Baron J.
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21st Oct 2019, 07:53 AM #35Most Valued Member
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Thanks Baron,
I am yet to measure both fields separately but I suspect they are not equal by a long shot. I'm confident that the motor does not turn because of the faulty field windings.
Wrt scraping. Yes it's bloody tiring that's for sure. Slow and steady is the go with frequent breaks.
Cheers.
Simon
Sent from my SM-G970F using TapatalkGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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3rd Nov 2019, 08:17 PM #36Most Valued Member
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Bit the bullet today and removed half of the field winding. I really have nothing to loose since it was in pretty bad shape. To my surprise it contained two different wire sizes.
31 turns of approx. 0.7mm ECW and several hundred (yet to count them all) of approx. 0.12mm ECW.
I'm a little confused, this does suggest two different windings (as descibed in the circuit schematic) yet only two wires entered the field windings from the circuit board. I was not expecting this and as such I didn't really take notice of how the two types of copper were connected.
Luckily, I am yet to remove the other side of the field winding. I will do this in better light when I have plenty of time and will take better care to see how it all goes.
Here's a pic for anyone interested...
Simon
Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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3rd Nov 2019, 08:35 PM #37
Hi Simon,
Its not uncommon to find that there are two different wire sizes used in a field winding. This is done to provide a heavier wire for making an external connection. You should find a joint somewhere in that lot where the two different wires have been joined. The only other possibility is a closed loop, a bit like a shading ring, a magnetic shunt, like in a small induction motor, but since it has an armature rather than a rotor, I doubt it.Best Regards:
Baron J.
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3rd Nov 2019, 08:54 PM #38Most Valued Member
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Thanks Baron,
Guess I'll find out when I remove the other half.
Do you think I can form those windings on a suitable sized jig spun using the lathe and then slide in place or will I need to wind it straight onto the former?
Winding straight onto the former will be awkward and take forever!!!
Simon
Sent from my SM-G970F using TapatalkGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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4th Nov 2019, 06:08 AM #39
Motor Rewind !
Hi Simon,
Yes I'm sure that you can.
Rewind the coils in the same way as it was originally done ! Make a wood former, three pieces of plywood screwed together to form a bobbin. Stick it on a mandrel using the lathe and wind away. If you use the weight method you won't have to count the turns. Alternatively you will have to rig up a counter of some sort.
Wrap the coil in fabric tape in the same way as it was originally and hook it over one side and then form it to fit the other side, putting in the wedges to hold it in place. Make sure that you get the winding direction correct on each side or it will just buzz when powered up. Normally the winding would be shellacked after fitting, to provide insulation and hold the winding rigid.
The hard bit is getting the former the right diameter. If you can get the other coil out in one piece, you could use it as a guide.
NOTE:
If you haven't already removed the other coil, you can place the carcass in a vice and remove the wedges, then use a block of wood and a hammer to flatten the curved part on either side (top & bottom) so that the coil expands out of the slots, then it will just unhook. The new coil is put in place the same way, hook it in the slots and use a shaped piece of wood to form the curve just like the original ones.Last edited by BaronJ; 4th Nov 2019 at 06:28 AM. Reason: Added info
Best Regards:
Baron J.
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4th Nov 2019, 11:00 AM #40Golden Member
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Interesting thread here, motor winding is not that hard, you don't really have anything to lose - I rewound my mill motor from 1ph 240 to 3ph 240, check out the thread here https://metalworkforums.com/f65/t200...l-motor-rewind some of my pics show my hand cranked coil winder made from scrap timber, I watched some videos before I started - quite a few of them show guys in India rewinding motors and using an old piece of wood and a few nails as the coil former.
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4th Nov 2019, 03:50 PM #41Most Valued Member
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Hi family guy,
Yes I remember that thread. I even commented that I would never have the ability to do a rewind. Go figure! Never say never I guess.
Mine should in a sense be easier, it only has 2 coils.
I'm just thinking of a way to rig up a counter and then attach it to the lathe.
Simon
Sent from my SM-G970F using TapatalkGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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4th Nov 2019, 07:28 PM #42Most Valued Member
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Took the other side out this evening. I was a little more methodical this time. I used a heat gun to soften the glue and varnish. It was still not easy to remove.
This side will give me better info. I can make a former winder based on the sizing of this one.
Simon
Sent from my SM-G970F using TapatalkGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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4th Nov 2019, 07:41 PM #43
Hi Simon,
A micro switch would give you an electrical pulse per revolution. But you would need a solenoid operated counter.Best Regards:
Baron J.
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4th Nov 2019, 08:36 PM #44Most Valued Member
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4th Nov 2019, 09:08 PM #45Most Valued Member
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Hi Baron,
Yea I'm thinking of using an induction sensor and an electronic counter.
Hi Stu,
You have lost me. I'm guessing using the saddle feed as a means of keeping count?
Also, No I don't have a count yet. I'll do that tomorrow when it's quiet and I don't get any distractions....
Simon
Sent from my SM-G970F using TapatalkGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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