Discussions on characteristics of variablespeed pumps controlled by pressure difference

Deduces the simplified equations of head ratio and shaft power ratio of variablespeed chilled water pumps by introducing the conception of controlled pressure differential ratio β. Presents that β is the key factor to energy saving of variablespeed pumps by acquiring characteristics of variablespeed pump controlled by pressure differential with different β. Compares the β value of primary pump with that of secondary pump, and believes that the variablespeed primary pump is always better than variablespeed secondary pump in energy saving in the same condition.