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Generator test

Started by Snapey, Saturday, 19 May 2018, 04:29 PM

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KiwiCol

An a damn fine job you've made of it too Snapey!  Top marks,  now shout yourself a beer or 6 for saving that much dosh!
😎  Always looking for the next corner.  😎

Sweaty

Great work Pete & what a saving   :onya:

froudy

You made a damned good job of that seal Snapey :onya:

It's not available as a spare part, so either carefully stripping the original one off or making a new one is the only options available.

For future reference, how did you make it?
Assumption is the mother of all fuck ups!

Mister Fishfinger

Nice work Snapey.

Just in case anyone is interested (feel free to skip this bit if you hate electrics), there is reason why the meter reading takes time to settle down when you are measuring the resistance of a generator winding.

It's basically because the wires in the generator aren't straight. They are wound into coils, which means that they have inductance. From a DC point of view there's no difference between that and a straight length of wire, but things are different when the current isn't steady.

When you first attach the meter it wants to go from "no current" to "some current" instantly - but inductors don't let you do that. They only allow the current to increase steadily from zero. That's why the meter takes a little time to settle, it is gradually building up current in the coil. The more turns of wire, the slower it will go.

Anyway, the point is - nothing to worry about, just wait till the reading is stable and you are good to go.

grog

Great job Snapey. agree, how did you make it?

Blubber

Nice outcome, good price too  :onya:
Wreck-it Richard - one of the unDutchables

Snapey

Quote from: Mister Fishfinger on Wednesday, 30 May  2018, 06:43 PM
Anyway, the point is - nothing to worry about, just wait till the reading is stable and you are good to go.

I now understand that I need to wait for the meter to settle before I get a good reading so let me tell you what I observed when I had the old and new stator together.

The ohms readings on both stators were well within tolerances ... 0.2 to 1.0 but at 5000 rpm both were below 60 volts.
Readings between the wires and laminations on the old stator all came up at about 0.4 ohms whether + or - was earthed.
The same test on the new stator showed completely different results but I forget if I earthed the positive or negative. Let's say the negative probe was on the wire (any of the three) and the positive earthed on the laminations the ohms meter would flash different high readings. If the probes were reversed I'd get no reading at all.

If you can understand that please explain.
If you look like your passport photo then you're too sick to travel.

Snapey

The rubber seal started the day as an off cut from a sheet of 1/2" die rubber. Bandsawn a linished  to size then the mounting groove cut with a 1/4" grinding wheel so the whole thing fits the casing but just proud of the surface.

Now the tricky bit. The wires are 2.25mm diameter so that's the size drill I used for the three separate holes knowing they'll be bloody tight. I have a scriber that's 3.0mm diameter that's pushed through a hole in the rubber and also a piece of thin wall brass tube also 3.0mm diameter. By pushing the point of the scriber into the brass tube I can now get the tube through the hole. I can now push the wire in to the tube and when sliding the tube out of the hole I'm left with the wire in the rubber.

Repeat two more times.

Maybe a few pictures in the morning might help.
If you look like your passport photo then you're too sick to travel.

Speedy1959

Its a good job you are into Rubber Snapey !!
:stir:

Irish in Oz

Quote from: Snapey on Wednesday, 30 May  2018, 09:57 PM
Quote from: Mister Fishfinger on Wednesday, 30 May  2018, 06:43 PM
Anyway, the point is - nothing to worry about, just wait till the reading is stable and you are good to go.

I now understand that I need to wait for the meter to settle before I get a good reading so let me tell you what I observed when I had the old and new stator together.

The ohms readings on both stators were well within tolerances ... 0.2 to 1.0 but at 5000 rpm both were below 60 volts.
Readings between the wires and laminations on the old stator all came up at about 0.4 ohms whether + or - was earthed.
The same test on the new stator showed completely different results but I forget if I earthed the positive or negative. Let's say the negative probe was on the wire (any of the three) and the positive earthed on the laminations the ohms meter would flash different high readings. If the probes were reversed I'd get no reading at all.

If you can understand that please explain.

To do a proper test you need one of these. The insulation on the windings are leaking to earth. It's like pressure testing a water pipe with a hydraulic pump.
I have this one with me, one in the workshop and my son borrowed the other one.

Snapey

What I'm not understanding about this Jeff is the readings I get between the wires and the laminations. When I used to wind alternator stators one of the tests was to make sure a wire wasn't shorting out on the laminations. If it did it failed. I'm getting these readings on the good stator.
If you look like your passport photo then you're too sick to travel.

Irish in Oz

With your new multimeter and new stator there should be zero resistance between cable ends and laminations or earth (frame) when bolted in to bike.
The reason for a megger (insulation tester) is  to pressure the insulation on the coil to make in leak to earth.
A ohm meter cannot do this, as I said above its like water in a pipe with a tiny pin hole and you can't find it but if you increase the water pressure you may then see the leak.
Anyway I've given away to many trade secrets now.

Irish in Oz

Quote from: Snapey on Thursday, 31 May  2018, 02:53 AM
What I'm not understanding about this Jeff is the readings I get between the wires and the laminations. When I used to wind alternator stators one of the tests was to make sure a wire wasn't shorting out on the laminations. If it did it failed. I'm getting these readings on the good stator.
As a matter of interest who where you doing the alternator stators for!

Irish in Oz

I remember working on some bigger than this.

Snapey

Quote from: Irish in Oz on Thursday, 31 May  2018, 03:17 AM
As a matter of interest who where you doing the alternator stators for!

Email Jeff. I was looking after the Possis winding machines doing alternators for Ford, Chrysler & BMC. That was 50 years ago but I remember having trouble with some bad insulation material allowing the windings to short out on the laminations.
If you look like your passport photo then you're too sick to travel.

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