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Is it possible to start 3 pumps with one VFD? when pump 1 is running it should put it over to bypass contactor and then start Pump 2 on VFD and then the same for Pump 3?

As per the requirement given above, the VFD will be used only for smooth starting and stopping of the pump. The VFD is not used with pump continuously for energy saving purpose.

It is not recommended to use VFD for the above functional requirement of start and bypass application, because when bypass contactor is ON, the 3 phase input power supply will be connected directly to the drive output through bypass contactor. If input supply is directly connected to the output of VFD, it will damage the IGBT's of the VFD. Refer the highlighted warning screen shot below from ATV61 VFD installation manual.


To avoid direct line supply to VFD output, if we disconnect the VFD output contactor after acceleration to full speed from VFD and command (switch ON) the bypass contactor, it will lead to power disconnection to motor for 1 sec, hence there will be drop in motor speed and hammering effect during change over from VFD to Bypass. Hence this operation with VFD is not recommended.
However ATS48 soft starter can be used to comply the above functional requirement. The customer can use ATS48 soft starter with the control scheme screen shot attached below




 
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