Technical and economic considerations for the application of permanent magnet brushless motors in evaporative water coolers

Evaporative coolers due to their low cost are used in hot and dry regions of many countries especially in Iran. Conventional evaporative coolers use single-phase induction motors (SPIMs). But the benefits of these motors are very low, and their substitution with high efficient electrical motors is considered by industrial parties. In this paper, the details of using the brushless motor in the application of evaporative cooler are presented. A 1/2 hp brushless motor and drive are designed and built. This motor- drive is tested by a dynamometer and standard testing equipment. Also, for the approval of this motor-drive, a 5000 m3/h direct evaporative water cooler equipped with this motor is examined under the airflow rate test in the reference laboratory. The results obtained in both tests are compared with the test results of a typical SPIM. The results verify an increase of at least 60% for energy efficiency compared to evaporative coolers equipped with SPIM. Moreover, a new control scheme based on power control instead of speed control is proposed to stabilize the outlet airflow rate. The results indicate that use of brushless motors in this application can offer considerable energy saving, and helps to protect environment.