The heating, ventilation and air-conditioning control system using D71 inverter has been put into operation for more than three years, and has achieved good economic and social benefits:

• The control device operates reliably, has good environmental adaptability, can resist harsh environments such as oil pollution, dust and damp heat, and has a low failure rate;

• Excellent current limiting characteristics, strong overload capacity, can effectively reduce frequency conversion overload, overcurrent protection, and maximize production continuity;

• The central air-conditioning system adopts frequency conversion closed-loop control, with fast dynamic response and high degree of automation, and the entire system realizes digital and intelligent control;

• The economic benefits are remarkable, the basic energy saving effect is 35% to 55%, and the entire investment increased by the frequency conversion control system can be recovered in more than one year.