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Thread: Dead Stator - ideas?
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23rd Apr 2020, 07:37 PM #31Diamond Member
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So the first layer of windings was reasonably neat, the second layer a little more random, and after that I tried to avoid overlaps, but it became very difficult to control. Also, it was pretty much impossible to get the 1mm dia wire to sit flat down through the former. The end result was that I was left with about 500mm of wire I couldn't fit onto to the coil. This is how it looked:
IMG_3101.jpg
Joined into the other coils with heatshrink and everything smooshed into place:
IMG_3102.jpg
And evidence covered up:
IMG_3104.jpg
And then just reconstruct into a pump (Grundfos have excellent videos on how to reconstruct a multi-stage pump - sooo many bits to be put on the right way in the right order):
IMG_3105.jpg
It runs, and the app seems to think it's OK:
IMG_3106.jpg
So now need to hook it up to a tank and test it...
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24th Apr 2020, 12:53 PM #32Diamond Member
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So this morning I had the chance to hook the pump up to a tank. The good news is that it appears to be working perfectly, the bad news is that I should have made more of an effort with varnishing the coil - the motor has a sort of grinding buzz as if something is rubbing, but I worked out it's the intermittent energising of the coil by the variable frequency drive. It's not the worst thing in the world, but it'd be nice if it wasn't so noisy.
I did spray the coil liberally with circuit board lacquer from both sides, hoping the thin lacquer would wick into the coil. However being so thin, a fair bit dripped off, and I don't really know how far it penetrated.
I think my three options are to ignore it, try spraying it with more lacquer, or try dipping it in varnish, the latter which I'd have to hunt down if it's a special kind.
In the mean time I think I'll commission it in a nursery where they water from a tank and the current pump is a bit too small, and see how it behaves.
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24th Apr 2020, 05:36 PM #33
Hi Rusty,
You might find that some of the spray varnish has got onto the inside wall of the stator surface and is rubbing slightly at some point. If this is the case the noise will reduce with use as the rotor warms up and wears it away.
whilst the rotor will be accurately centred, the stator can be a few thou away from true, particularly if there is a bit of debris that is trapped under one edge when you put it back into the case.
Anyway you have successfully repaired the machine, saved some money and got it back in service.
Good one.Best Regards:
Baron J.
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24th Apr 2020, 08:25 PM #34Diamond Member
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I'm pretty confident there's not interference between the rotor and stator - I ran some 400 grit wet and dry over the inside of the stator before assembly to remove minor residual surface rust from its time being half immersed, and spent a while remounting the rotor and front plate to make sure everything was spinning freely. The rotor is a fancy permanent magnet type, so I was a bit concerned about bits of random metallic crud sticking to it, but I think I'm OK.
I'm hoping it's all good. If you want to know what it's worth, google Grundfos CMBE 3-62 . If I get motivated, I might have a go at talking to it over its RS485 "Genibus" interface, which looks to be Grundfos's in-house modbus-like protocol.
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