求翻译：水泵的变频调速是指水泵在可调速的电机驱动下运行，通过改变转速来改变水泵运行的工况点。以往，人们对水泵自身调速后功率与转速（频率）之间的相关性研究的很多，并基于流体力学的相似定律理论，得到水泵变频前后，轴功率比与转速比成三次方关系[ ]。该相似定律被广泛应用于水泵变频后运行工况的计算和相应系统的运行调节。但是在开式系统中，水泵变频前后的效率发生很大的变化，致使定律该不适用于水泵在开式系统中的变频调节[ ]，可仍有部分学者在开式系统中运用水泵的相似定律进行调速控制[ 、 、 、 ]，这样显然是不对的。是什么意思？

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Water Pump frequency is the water pump adjustable speed motor drive is running by changing the speed of the pump running to change performance point. In the past, people of pump speed after its own power and speed (frequency) dependencies between research and is based on many similar law theory of c

The water pump frequency conversion velocity modulation is refers to the water pump in under the motor-driven which may modulate velocity to move, changes the water pump movement through the change rotational speed the operating point.Formerly, people after water pump own velocity modulation power a

Pump frequency conversion timing refers to pumps running in adjustable speed motor drive by changing the speed to change the operating point of the pump. People used to pump its own variable speed power and speed (frequency) correlation between lots, and based on law of similarity theory of fluid me

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