Performance Enhancement of Evaporative Water Cooler Equipped with Permanent Magnet Brushless Motor Drive Based on Power Control Strategy

Abstract

Evaporative coolers with single-phase induction motors (SPIMs) are one of the least efficient and most commonly used electrical power consumers all over the world. Recently, it has been suggested to substitute SPIMs with higher-efficiency motors, such as permanent magnet brushless (PMBL) motors. However, control method for brushless motors often work based on speed, while laboratory tests indicate that, due to fluid characteristics of the blower, the airflow rate is not just related to the speed, where increasing the cooler’s duct length reduces the airflow rate, thereby preventing the desired airflow rate to be reached. To overcome this problem, in this work, a new power based control scheme has been developed to stabilize the outlet airflow rate instead of the speed control. In this approach, output power of PMBL motor is regulated around a set point power corresponding to the desired air flow rate. A 5000 m3/h evaporative cooler equipped with brushless motor was tested with both constant speed and power control strategies. Results indicated superiority of the proposed brushless motor drive and power control scheme.