We actually don't use PDMA, but I'm interested in it. Commeting based on my limited understanding.
[quote]Theoretically this test should be equivalent to the Baker surge testing. I haven't been able to document enough cases yet to conclusively prove that one test is superior to the other. [/quote]
I guess you're saying they're equivalent from the standpoint they are both intended to detect turn to turn shorts. In that respect I'd point out an obvious difference. Surge testing creates a higher turn to turn stress than motor operation (especially on the first few turns which are most vulnerable to damage from system transients). In this respect is is similar to a high-potential test: it is more likely to find a weakness but also more likely to damage a motor during the test. That's a fine line to walk, but still makes the surge test valuable imo when used with proper understanding (don't do it unless you are prepared for a failure with a spare or time to rewind the motor).
A disadvantage of the inductive imbalance imo - no standards. And as you say many false alarms. Although I think many of the false alarms can be ruled out as a stator (shorted turn) problem based on RIC test. But if we have high rotor influence, we don't know whether it is actual rotor problem or just normal residual unbalance… still a lot of unknowns. Doesn't seem really useful to me. Most motor repair shop people I talk to say that for purposes of evaluating the rotor they would very much prefer a different test: the "single-phase" rotor test at roughly 25% voltage with manual rotation of the rotor and checking for stator current variation. But of course that is a much more difficult test to set up.