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marksl

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Reply with quote  #16 
Quote:
Originally Posted by MarkL
Funny Enough Pete I was kinda thinking the same Last Night, well the Upper case is me and I am in Ireland, the Other Chaps in Australia I think.. [biggrin][biggrin][biggrin][biggrin]







Yep I'm in Australia , can't you tell from the acent mate ! lol
Noknroll

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Reply with quote  #17 
QUOTE:well the Upper case is me and I am in Ireland, the Other Chaps in Australia I think..

So his writing will be upside down........
MarkL

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Reply with quote  #18 
Nok..I was strangely surprised when I was in Melbourne a few years back that you werent all upside down ;-)

@ MarksL That unit for use on a 75mm shaft comes in around €1200. in our money, retailing, but no Idea what way it would be priced your side of the world....
qnʇ Wɐʎqǝ ᴉʇ ʍᴉll looʞ ʇɥᴉs ʍɐʎ ʇo ʎon  [biggrin]
Ron Brook

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Reply with quote  #19 
If as an end user you have followed all of the rules to eliminate EDM, then there is no reason to monitor shaft voltage.  There might be a need to diagnostic look for them, in which case I highly recommend the PEM Rogowski Coil and an O'scope.  The coil is electrically resonant to 10 kHz, so it will see any and all current frequencies that might be riding on the shaft.
As far as monitoring power, I used the PDMA Emax unit and had excellent results identifying unbalanced voltages and currents, harmonic distortion, etc.  The results tables and graphs are excellent.  I even used it one time to identify a bad tach on a dual VFD driven motor.  I used it to monitor the voltage and current waveforms coming out of the six power leads.  There were places in the waveform where all of the voltages and currents would drastically fluctuate at the same instant in time, no matter which leads I was comparing, V1,V1  or V1,V3, C1,C2,C3, etc.  from both drives.  Since there was only one common factor that could affect them all at the same time, I had the end user replace the tach........fixed!
RickP330

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Reply with quote  #20 
I am interested in this topic.  Can anyone share if they had success in using their Vibration data collector to monitor 3 phase motor current?  I would like to give this a try on a 8MW motor we are maintaining.
Rick
Walt Strong

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Reply with quote  #21 
I have been doing motor current spectrum analysis on both induction motors and induction generators on Hydro turbines for many years using a vibration analyzer. I use a CSI 2120-2 analyzer with a Fluke clamp-on current transformer and a homemade resistor box. The vibration analyzer can only measure AC voltage, so a resistor is needed to convert dynamic current into a dynamic voltage signal. I have not only found defective motor rotors, but also have detected broken gear teeth, broken gear shaft, abnormal pulsation, and V-belt defects. Current analysis on a large 8 MW motor will probably require a low voltage current tap to get appropriate signal for the analyzer. I have done measurements from a low-voltage secondary circuit with a clamp-on transformer and also with direct (voltage) connection to a permanent current meter. There are a lot of technical articles on the Internet that will assist you in interpreting your measurements.

Give it a try!

Walt
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