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Mv Soft Starter Problem


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Has anyone ever had a problem with the motor getting up to approx 150rpm (1485rpm rated) and the motor stalling with severe vibrations. I just recently read an article about crawl speed (1/7th or 1/13th of rated speed) causing this same problem. I will not get a chance to start the motor for several days due to construction activities. When I get next chance, I plan on increasing the initial voltage to 65% (from 40%) and reducing the ramp time to 4 seconds (down from 8 sec) in an attempt to have enough momemtum to have the motor drive past this "crawl speed".


Also, on a previous attempt to increase initial voltage and reduce ramp time (70% voltage and 2 sec ramp), the soft starter went out on phase loss. However, no fuses or circuit breakers tripped. How could it be that the soft starter that it had a phase loss? Could this be from excessive harmonics generated by the soft starter, causing it to incorrectly sense incoming waveforms, then misfire causing an errant "phase loss" trip.


Any help is appreciated. The soft starter was manufactured by Motortronics.


Thanks, Nukee

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Hello Nukee


Welcome to the forum.


Next time you start th motor, see if you can measure the speed where the vibration becomes a problem. If this is 1/7 or 1/13 of synchronous speed, then you have a crawling problem.

If the speed is different, then I would look at coupling alignment, motor and load mounting etc.


Best regards,


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