3 replies to this topic

[jraef]

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.

[marke]

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,

[jraef]

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.