Pump and motor speed

The available motor speeds (RPM, revolution per minute) for a standard alternating current A,C.) electric motor are based on following equation for 60-cycle current  

Nm is the number of pole in motor and it equals to 2,4,6, 8, 10, and 12. The available corresponding motor speed is 3600, 1800, 1200,900, 720, and 600 rpm. The actual motor speed is slightly less than the rpm calculated by Eq. (6) due to electrical slippage between motor rotor and stator. For example, the speed of a two-pole motor is 3450 to 3550 ipm, not 3600 rpm. 

Pump speed will be the same as the motor speed, if pump is directly connected to the motor shaft. 

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Consequently, if the pump and motor. speed were reduced by 50% ... 

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