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Old 10-09-2014, 01:06 AM   #1184 (permalink)
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Pulse Test

Originally Posted by MPaulHolmes View Post
The books way of doing it was to run the motor unloaded for one test, and then locked rotor for another test. From those two tests, you deduce like 15 different things. One of those is the rotor resistance (like number 15 in that train wreck process.). We still need the rotor inductance. Then the time constant is L/R.
The Industrial VFDs that I use at work refer to 2 tests. One is a 'Static Tune', where the motor is coupled to a load. This is not as accurate but it gets you some numbers that are close. The test mentions something about a DC voltage applied, I'm guessing it's at least 3 DC voltages to involve all of the coils, but it's a short duration and somehow they measure inductance and resistance. The DC is sequenced so that it does not induce rotation.

The other is a 'Dynamic Tune', where the motor is decoupled from the load, motor only. The motor gets a series of pulses and rotates 1/4 to 1/2 a turn.

Each vendor appears to do it differently (slightly) and considers this part of their own 'secret sauce'. I can't find any documentation on how it's done. I'd like to try this method, since it is one of very few things that I've seen consistent from one VFD to another. But that's all the info I have so it's not much help.

On another topic, if you are open to it, I'd like a copy of the source. PM, or ftp, or whatever works for you.

I'll likely get lost trying to follow it .. but I may not.
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The Following 3 Users Say Thank You to thingstodo For This Useful Post:
e*clipse (10-10-2014), freebeard (10-09-2014), MPaulHolmes (10-09-2014)