High volumetric efficiency is more than 95%. Power consumption is 30% less than machines haying fixed displacement pump. Cooling water requirement of hydraulic oil is between 1/3 and 1/2 of fixed pump requirement due to without extra hydraulic oil overflow. Therefore there is longer life for the seal of the pump than fixed pump. On the basis of proportional technology, the combination of electrical and sensor technology reaches the success of dosed loop variable pump. Through the control of pressure and flow by a proportional valve, and continual monitoring of pressure and flow by the pressure sensor and plate angle sensor, it leads precise pressure and flows to save energy.