There are no specific industry standards related to the maximum voltage drop that a motor is allowed to cause during starting. NEMA standards do say that the motor must be capable of operating successfully at up to 10% deviation from rated voltage, implying that the motor must successfully...
If you determine the power output of the motor, and can determine the motor speed and the pump speed, then the power to the pump is equal to the power output of the motor multiplied by the ratio of PUMP SPEED/MOTOR SPEED. The loss in the ECC is equal to the difference between the motor output...
