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I have posted the following update GS Charging health relating to various tests of the actual stator v.s. the whole set of charging system tests: The points made below was one of the major factors in developing the "Quick Test".
Reading just this limited amount of information, there should be ample information to conclude that the testing of a stator amounts to the testing of the insulation. Insulation tests can not be done conclusively with a low voltage ohm meter (like measuring sub ohm resistance with a 9V battery).
Standard engineering insulation tests that have been developed are based on much higher voltage breakdown. Unless there is a high voltage consistent with the expected operational range of use, then any positive test results will be inconclusive
So when I say a conventional stator test (non - MEGGER) can only unambiguously proves a fault, it is because it those tests do not fully test the stator to the level required in operational use, then concluding that the stator will pass in operational use leaves a large gap in performance and therefore an apparent ambiguity in the results.
The stator test is only valid is it fails, as if it fails at a low level you can be assured it will fail at a higher level. I can state this in the following RULES for testing stators.
This brings us to the following LAWS for Stator testing (i.e. those related to Phase B of the stator pages)
FIRST LAW OF STATOR TESTS:
ANY POSITIVE RESULT of a STATOR TEST HAS AN AMBIGUITY PROPORTIONAL TO THE UNTESTED OPERATIONAL STRESS.
SECOND LAW OF STATOR TESTS:
ANY NEGATIVE RESULT of a STATOR TEST IS A NECESSARY AND SUFFICIENT CONDITION TO DECLARE A STATOR BAD.
What is positive and what is negative you might ask? You will have to refer to the state ranges of the test and deduce make your decision based on the cost of making such a decision. The costs will vary depending upon your situation.
For example, the stator voltage tests say to have between 65-80 volts at 5000 RPM. Say you have two stator at 75 VAC and one at 65 VAC. Is that good or bad? Well it depends. There is a clear indication that there is a degradation in the single low measurement (there is imbalance), It is still good enough withing the stated ambiguity of of the First Law. So the question of cost is, are you willing to forgo the maintenance and increase your probability of inopportune failure? Or do you want to incur the expense to change something that is still operational but appears to be on the way out. This decision has nothing to do with the test or whether something is good or bad, but instead determines the optimal decision for maintenance based on the likelihood of failure and cost.
And here are some updates with background to the Phase B tests that focus on the stator alone.
A revised test is at this link; The actual test is on Page 6 of 9. We added the leg to ground AC voltage test as this helps isolate insulation breakdowns to ground using the relatively high 60-80 VAC stator voltage when it is open loop.
Link to Revised PHASE B of Stator Pages with discussion of testing methods:
http://www.keepandshare.com/doc/3977...4-pm-649k?da=y
A revised test is at this link; The actual test is on Page 6 of 9. We added the leg to ground AC voltage test as this helps isolate insulation breakdowns to ground using the relatively high 60-80 VAC stator voltage when it is open loop.
Link to Revised PHASE B of Stator Pages with discussion of testing methods:
http://www.keepandshare.com/doc/3977...4-pm-649k?da=y
Reading just this limited amount of information, there should be ample information to conclude that the testing of a stator amounts to the testing of the insulation. Insulation tests can not be done conclusively with a low voltage ohm meter (like measuring sub ohm resistance with a 9V battery).
Standard engineering insulation tests that have been developed are based on much higher voltage breakdown. Unless there is a high voltage consistent with the expected operational range of use, then any positive test results will be inconclusive
So when I say a conventional stator test (non - MEGGER) can only unambiguously proves a fault, it is because it those tests do not fully test the stator to the level required in operational use, then concluding that the stator will pass in operational use leaves a large gap in performance and therefore an apparent ambiguity in the results.
The stator test is only valid is it fails, as if it fails at a low level you can be assured it will fail at a higher level. I can state this in the following RULES for testing stators.
This brings us to the following LAWS for Stator testing (i.e. those related to Phase B of the stator pages)
FIRST LAW OF STATOR TESTS:
ANY POSITIVE RESULT of a STATOR TEST HAS AN AMBIGUITY PROPORTIONAL TO THE UNTESTED OPERATIONAL STRESS.
SECOND LAW OF STATOR TESTS:
ANY NEGATIVE RESULT of a STATOR TEST IS A NECESSARY AND SUFFICIENT CONDITION TO DECLARE A STATOR BAD.
What is positive and what is negative you might ask? You will have to refer to the state ranges of the test and deduce make your decision based on the cost of making such a decision. The costs will vary depending upon your situation.
For example, the stator voltage tests say to have between 65-80 volts at 5000 RPM. Say you have two stator at 75 VAC and one at 65 VAC. Is that good or bad? Well it depends. There is a clear indication that there is a degradation in the single low measurement (there is imbalance), It is still good enough withing the stated ambiguity of of the First Law. So the question of cost is, are you willing to forgo the maintenance and increase your probability of inopportune failure? Or do you want to incur the expense to change something that is still operational but appears to be on the way out. This decision has nothing to do with the test or whether something is good or bad, but instead determines the optimal decision for maintenance based on the likelihood of failure and cost.
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