Posted by Hendrik on December 17, 2014 at 15:40:19 from (77.171.150.157):
Question for sparkies. I have a 25 year old 3-phase asynchronous motor of 0.37 kW, driving an overhead door.
The motor is set up for star mode (not triangle). Between junction point (L1 and L2) I measure 42 Ohm, and the same value between (L1 and L3) and between (L2 and L3). Between L1 and the star point I measure 21 Ohm, and the same value for L2 and L3. So all three coils seem to be nicely identical.
I have a new motor with identical specs, although of different make. For this new motor the resistance values are 54 Ohm and 27 Ohm respectively. The new motor was bought because the old one trips the safety relay in the control box of the overhead door drive at irregular intervals.
Is the old motor bad because the Ohm values are higher? Or is the problem (tripping) somewhere else? I'm really puzzled here.
Note: I'm writing from The Netherlands where we have 230/400 V 3-phase at 50 Hz.
Any and all insight you can provide will be much appreciated. Thanks, Hendrik
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