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Home Workshop > General Area > General > Accessing motor Star point

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Accessing motor Star point

Accessing motor Star point

Hi Folks,
I'm trying to get to the star point of a fractional HP suds motor (only 3 terminal inthe junction box) so I can run it 220 delta but the star point is at the closed end of the motor housing and I can't see how to slide out the field coils. Ther are no retaining screws on the outside of the housing unless they are hidden under the rating plate ? There is not a lot of meat onthe iron par of the assembly and the winding are very fine. So I'm asking for advice before doing anything that might ruin it
Thanks Tony
http://homeworkshop.org.uk/components/com_agora/img/members/435/mini_21012017-1809_field-coils.jpeghttp://homeworkshop.org.uk/components/com_agora/img/members/435/mini_3wires-out.jpeg

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Anthony Ray
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Re: Accessing motor Star point

Hi Tony,
I would not try to extract the windings en masse, nor remove the stator cores. The start point will be in amonst the sleeved tails that can be seen on the end of the windings as you have taken the photo. You will have to cut some of the ties and tease the sleeved tails away from the windings. It should be pretty obvious which are the single tails that end up outside the motor and which are three singles heading to a common sleeve. The sleeve at 11o'clock in your photo looks a likely candidate and if you see there are three singles at the other end then I'd be even more confident.

- Richard -

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Richard Shute
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Re: Accessing motor Star point

How many poles does it have? The more poles the more joins there will be in addition to the star and the leadouts, expect at least two. Tricky to give guidance on whereabouts the star will be since joins are often folded back on themselves, but often either opposite the leadouts or near them, seldom just 90 degrees out. The star point will be the only three way joint. When you put it back together you'll need to rebind everything using thin ribbon or stout yarn and then treat with some shellac based product (button polish for example, thicker if you get it) and cure in a cool (electric) oven (80C will do).

Nick

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Nick Kempley
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Re: Accessing motor Star point

I don't think that you will have a star point. If it's delta wound then there should be the end of one winding, the start of the next and a leadout wire bundled together times three and that will be it.

Mick

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Re: Accessing motor Star point

Look around the outside of the casing for any evidence of screw heads. I've seen windings secured by very short countersunk screws before. Other than that it was probably pressed or glued in. The trouble is that if you try to pull it out you'll probably peel off the end laminations and compromise the insulation. I fear that your best bet is doing what Richard said, tease out the star point. Lacing it back in might be a challenge though.

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Re: Accessing motor Star point

Hi Thanks for the responses to aswer question in order of posts

Richard - I don't think the sleeve you see at 11 oclock is a sleeve, when I peer down the bore I can see some fibreglass sleeving at the far end, hence I think the star point is down there and I can't access that end due to lack of provision of a removable end plate.

Nick it s 2 pole so ~3000 rpm  and it would make sense to have it at the end where the existing termination  are so they could all be lead out to the terminal box if it were configured as a dual voltage motor.

Mick - I'm assuming its star wound as the main drive motor on the mill was thus - that motor was not marked up as dual voltage but when I took the lid off the terminal box it had the usual 6 terminals and links and I reconfigured it for delta,  it runs a treat on a VFD.
So I'm assuming the sud motor  is wired in star but no way to tell unless I can find the star point ?

Pete - problem is if the star point exists its almost in accessible; if I were a trained key hole surgeon it might be possible. I'll have a look for thoes retaining screws.

Perhaps I should just put it back together and list it in the ads and get a few quid towards a replacement single or dual voltage pump ?

Thanks

Tony

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Re: Accessing motor Star point

Arg, it's just for a suds pump? I totally missed that. Just wire it up to 240 mains on two of the phases and stick a capacitor on the spare leg - it'll be reet!

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Re: Accessing motor Star point

I'm with Pete, except for one thing: just don't connect it. Suds is only suitable for machines that are a) used every day for several hours, b) you don't care about and will never clean. The one exception to this in my workshop is the horizontal bandsaw where a good flow is needed to clear the tooth gullets and it moves quite slowly so the suds don't fly around the workshop. Use neat cutting oil if needed, hand applied or air blown.

Nuck

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Re: Accessing motor Star point

Hi I refered to finding the star point in my post about a Progress 2G drill. I've just done it on a 3/4HP Hoover motor. It was easy to spot the star point as with all the others I have done including a suds pump and a table drive motor, it was on the shaft end of the windings opposite to the connection end.  Digging it out of the shellac covered fabric tape is althogether another matter, I did it,but risk of collateral damage is very high. I severed a copper winding wire just under the fabric easily joined again but not ideal.  Attaching the new leads is easy but binding it up again with thread is not easy as there is little space th thread through under the windings.  Previously I sprayed all my work with conformal coating sold by Rapid Electronics but the spray can failed to work so I just gave it a spray of clear acrylic paint, I have just remembered I have a can of Knotting that would have worked oh well.  In the end if I messed it up I wouldnt have lost much as I can't use a delta connected motor so it's modify or chuck and I suspect the value of a 1950-'s 3 phase motor is about £5.
Ashley

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