Power characteristics of a variable hydraulic transformer

The flow control of hydraulic transformers is a great challenge. To meet this challenge, a new kind of hydraulic transformer, variable hydraulic transformer (VHT), is proposed in this work. This paper focuses on the power characteristics of the newly proposed VHT, including instantaneous power, average power, power pulsation, and efficiency. In the analyses, the concepts of efficiency, input power, output power, starting angle, and ceasing angle are defined or redefined. To investigate the power characteristics, their models are derived by considering the governing factors such as the control angle of the swash plate and the structure of the port plate. This work highlights that the load flow can be adjusted by adjusting the control angle of the swash plate, and the power characteristics at the B-port produce a remarkable change. In addition, the VHT has a starting angle and a ceasing angle, and these two angles can be adjusted by the influencing factors. The results reveal that the power pulsation and the jump points of the instantaneous power are the primary causes of a less smooth work. Then, it is shown that the control angle of the port plate, the control angle of the swash plate, and the pressures at the ports are the three key elements for a stable operation. The results also reveal that the adjustment of the influencing factors can improve the efficiency