Economically Efficient Green Hydraulic Lifts

The general trend in the lift industry is towards lifts with lower energy requirement. hydraulic power units with inverters were introduced to decrease energy consumption for heavily used lifts. Since existing solutions are generally more demanding and rather costly these systems have not found enough appeal yet. A compact, simpler and cost-effective solution to compete with advantages of the conventional hydraulic elevator system is necessary to make energy-efficient solutions more attractive. With the use of an inverter the pump outputs just enough flow for the momentarily targeted speed. When pump leakage increases due to higher load and/or oil temperature, the car speed decreases which results in longer travel time and uncomfortable ride. Therefore, pump flow should be regulated according to the load and oil temperature to assure targeted speeds and good ride-quality. In this paper, a sensor-less load compensation solution that basically consists of a control valve and an inverter with sophisticated hydraulic software module is introduced to assure targeted speeds under all load conditions. The solution has no sensoric interface between the control valve and the inverter, works with open loop control and also provides an extra energy saving mode. All these advantages not only make the solution an energy efficient one but also an economically-efficient one as well. The paper gives the details of the solution and features implemented in the development of the control valve and the advanced inverter software.