Implement of Increment-model PID Control of PLC in Constant-pressure Water System

Because of the continuous change of surroundings temperature, the flux of cooling water should not be constant. Then the water undulation, direct ratio to the square of water flux, is so large that it can reach to the half of total head. It is means that much electric energy is wasted. In order to control the water pressure value and retrench power, the system introduces FX2 series programmable controller as kernel control unit, uses digital PID technique to control the output frequency of transducer automatically. One pump is driven by the transducer, others is driven by industrial electric network. When transducer´s output reaches to the most but the power is shortage all the same, one pump will be driven by industrial electric network. If the total power is less than requirement, other pump will be start-up until the real water pressure reaches to set value. In this way, the electric energy will be retrenched.