Affects of series driven induction motors

[BrianKRogers]

What would be the affects on a 3 phase induction motor down-stream of another 3 phase induction motor? Basically, the first (and generally larger) is a centrifugal pump, 2-pole, used for mixing. The second (or down stream) pump is a 4 pole gear pump, used for recycle, usually smaller in size (about half the size of the mixing motor). When the mixing motor is running, the motive force is enough to start rotating the recycle pump. There is a significant change in the ampacity and rpm of the recycle motor. What affects does this potentially have on the motor and/or power transmission?

[marke]

Hello BrianKRogers

This configuration will obviously change the loading on the motor, and probably result in the second motor operating at increased load due to the reduction in suction required. I would expect tht the motor could run at a higher load with more product passing through it. This is dependant on the output pressure or head into which the pump is operating.

There is no problem starting with an already rotating motor unless the motor is driven by a variable speed drive.

Starting a motor that is rotating in reverse will lengthen the starting time and therefore increase the heating in the motor, and starting a forward rotating motor will shorten the start time reducing the heating in the motor, unless, due to increased flow, the start current needs to increase (to increase the start torque) in which case the heating will possibly increase.

 

Best regards,