ANALYSIS OF A DIGITAL PUMP WITH VARIABLE SPEED DRIVE

The interest in speed-control of hydraulic pumps is increasing with the electrification of mobile machinery. With speed-control at hand, it is tempting to use fixed pumps where variable pumps earlier have been used. However, it can be beneficial to use variable pumps in combination with variable speed since it can allow downsizing of electric machines and reduce losses. But there are downsides with conventional variable pumps, such as increased complexity, cost, and low efficiency. Digital pumps (i.e., pumps with a discrete number of displacement settings) can address these problems. This paper is focused on the performance of a digital pump, both efficiency-wise and from a dynamic perspective. Shunt-based concepts that can improve the dynamics during switching are proposed. Simulation results show that the concepts can reduce the disruption in output flow during switchings.