Brushless Motor Drive based on Power Control Method for Direct Evaporative Air Cooler

Abstract

Direct Evaporative air cooler (or evaporative cooler) with single-phase induction motor (SPIM) is one of the least efficient and commonly used appliances in Iran and over the world. For energy saving, new generation of evaporative coolers have been equipped with high efficient permanent magnet brushless (PMBL) motors. The control method of brushless motor is mostly based on the speed control, in which it works at two constant speeds. However, experimental tests show that, due to characteristics of the cooler’s blower, the airflow rate is not related to the blower speed alone and increasing the length of duct reduces airflow rate. To solve this problem, in this paper, a novel control method is proposed to stabilize airflow rate, in which, instead of using speed control method, the motor is controlled in constant power control scheme. On this way, a 5000 m3/h evaporative cooler equipped with brushless motor is tested in the reference laboratory under airflow test with speed and power control methods. The captured results verify the superiority of PMBL motor than SPIM, and also the performance enhancement of the cooler using power control rather than speed control method.