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pump reacceleration.


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#1 Guest__*

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Posted 11 October 2005 - 02:18 PM

We have ALSTOM sea water pumps ,our pumps stop in case for any reason we lost the power supply due to one of switchboard (MCC) incomers failure and will be waiting for manual start, my question is there any effect for the motor
or pump if we modify the control to run the motor automatically once the power supply restored back immediately and before the pump completely stop (reacceleration).
Regards,

#2 jraef

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Posted 11 October 2005 - 06:09 PM

If there is no check valve and pumps can spin backward after losing power, it is dangerous to re-apply power to them until the shaft has stopped rotating. You can simply use a delay timer to prevent automatic restarting for long enough to make sure the motor has stopped.

If there is no back flow problem, you should still make sure there is a small delay, such as 1 second, to ensure that the magnetic field in the motor is not still present when you re-energize. This will only be a problem if the power loss is very momentary. If you always have contactors or breakers that open and have to reclose to restore power, then that delay time would be unnecessary.
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#3 marke

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Posted 11 October 2005 - 06:30 PM

Hi jraef

I'm curious about the reapplying power when the "shaft is still spinning" I have done this many times with no problems, the only proviso is to ensure that the rotor field has decayed. For this, I allow a 1 second delay before reapplying power. Comments?

Best regards,

#4 jraef

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Posted 11 October 2005 - 06:37 PM

I meant that with regards to the shaft spinning backwards because of backflow. It will often break the pump shaft. The 1 second delay is for the field issue as you said.
"He's not dead, he's just pinin' for the fjords!"




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