SIMULATION OF A ELECTROHYDRAULIC LOAD-SENSING SYSTEM WITH AC MOTOR AND FREQUENCY CHANGER
Radek Maňásek · 2000
There is an effective trend using input energy of dynamic systems nowadays. It is the same in the branch design and control of electrohydraulic systems. We try to develop systems characterised by high efficiency coefficients. Standard electrohydraulic systems are characterised by low efficiency. A pump produces oil characterised by constant pressure and constant flow. As a result of this is energy wasted by stranglehold and by the pressure issue of the system. There are systems characterised by a higher coefficient of efficiency. The systems with constant pressure, which has better results and the Load-Sensing systems. The Load-Sensing system is the best, because the wastes by stranglehold and by the pressure issue system are minimal. There are more ways, how to realise such a load-sensing system, but the start point is the same. The flow is given by multiplication of speed and volume. So, if we want to change flow, we can do it by changing volume or speed of the pump. The first way is hydraulic load-sensing system and second one is electrohydraulic Load-Sensing (there is also third method – to change both of them). I am interested in the electrohydraulic load sensing system. In my way it consist of an asynchronous motor controlled by a frequency changer and a pump with constant volume. I assume, this concept is very useful, because it consists of parts with uncomplicated structure, which means no problems during work. The main part of my paper goes in the electrohydraulic Load-Sensing system. The scheme of this system is presented and itemised. There are presented models of items and solution of control circuits in the paper as well as the result of the simulation.