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Kone MX 20, not so mysterious now.
by on 03/02/12 05:28 AM
The ongoing story of the Kone MX20. Getting rewound now.
Last edited by Vic; 03/02/12 05:43 AM.
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#2843 - 03/04/12 12:28 AM
Re: Kone MX 20, not so mysterious now.
[Re: GreenPants]
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Joined: Apr 2011
Posts: 565
Vic
jack of all depts
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jack of all depts
Joined: Apr 2011
Posts: 565
orange county, CA
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There was a construction defect in the shaft design that let the water in, and the owner is going after the GCs bond. There are streaks of water going down inside the shaft, right behind where the motor cooling fan intake is, rusty rail brackets on that side of the shaft only, black mold on the drywall in that vicinity. Every other shaft is clean and dry, and every other motor reads very high K ohms to ground, or meg ohms. This motor got soaked.
This stator didn't implode, and throw copper balls all over. But it is shorted in one area. Each leg read about 1 ohm to ground, compared to where a good motor on an other running car reads very high K ohms, or megs, when checked in the exact same way. I had Rubin come out and double check my findings, and he confirmed the stator is shorted, as did the manager of the shop that the motor is at.
The short seems to be on the far side of a good bit of winding turns. Although we were reading only 1 ohm to ground, the motor windings will read very low, as they are very thick. So it's not like the output of the drive was feeding into a direct short, there was still a lot of winding turns, and some impedance, too. There was enough magnetic force generated through the remaining good part of the windings, for the motor to turn a few degrees at a time. But the current draw was very high, and the drive would crowbar itself off, on the max current parameter. And then as soon as the current subsided, the drive would turn on again, the car would move again, and then just as suddenly, it would crowbar to a stop again.
Only this effect happened very rapidly, in staccato succession, alternately trying to turn the motor a bit, then letting off, and the net result was a rapid pounding felt through the platform, motor, everywhere, sort of like a jackhammer.
The current limiting capabilities of the V3F25 drive allowed a certain amount of current flow, and at the same time acted like a safety valve. It would turn the motor just a bit at a time, but no fuses would blow, nor critical drive fault to keep it shut off.. Weird effect.
This near instantaneous crowbarring may have kept the windings from blowing into smithereeens, like you get when driving a hydro motor from an across-the-line starter, or the ac end of a gen set. I know what you mean, I'm used to seeing molten copper after a blow up.
Last edited by Vic; 03/04/12 12:39 AM.
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#3385 - 05/02/12 03:40 AM
Re: Kone MX 20, not so mysterious now.
[Re: theshaft]
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Joined: Apr 2011
Posts: 565
Vic
jack of all depts
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jack of all depts
Joined: Apr 2011
Posts: 565
orange county, CA
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#3393 - 05/02/12 11:00 PM
Re: Kone MX 20, not so mysterious now.
[Re: Vic]
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Joined: Apr 2011
Posts: 565
Vic
jack of all depts
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jack of all depts
Joined: Apr 2011
Posts: 565
orange county, CA
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When the motor was disassembled, the bearings got damaged.
As it turns out the bearings are not readily available, and had to be specially ordered from Europe.
When we took the motor to the job site today, we left it in the bed of the truck. We backed the truck up to the controller, hooked up the 3 phase, resolver, thermostor, jumped a bunch of stuff out, temporarily changed some parameters,
and then it ran!
Tomorrow we install it for real.
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