Performance Improvement of Evaporative Cooler Equipped with a Permanent Magnet Brushless Motor Using Power Control Method

Evaporative coolers, as one of the least efficient and commonly used electrical power consumers, are used in different areas in Iran. Recent government agencies have focused on the improvement of this consumer by modifying motor designs or the replacement of the single-phase induction motors with higher-efficiency motors, such as brushless motors. The control method of brushless motor, used in this application, is often based on the speed control which is constant (for example, two speeds high and low). However, laboratory tests show that due to special characteristics of the cooler’s fan, the amount of air flow rate is not related to the fan speed alone. Commercial evaporative coolers are designed for a certain length of the channel that is able to deliver its nominal flow. Increasing the length of channel by the owner can reduce the airflow rate and practically, despite the paid cost, no good airflow rate can be achieved. To remedy this problem, a new approach is proposed in this paper to stabilize airflow rate. For this purpose, the motor, instead of using the constant speed control approach, is controlled in a constant power approach. The details of the requirement’s design, the application of brushless motor in the evaporative cooler, as well as the results of the test of a 0.5 hp (horse power) brushless motor using the dynamometer are presented.  The results are compared with the results of a typical single-phase induction motor test. Afterwards, a 5000 m3/h evaporative cooler, equipped with brushless motor, is tested in the reference laboratory under airflow test. The test is carried out both in a constant-speed and in constant-power control approaches. The achieved results indicate the absolute superiority of brushless motor over single-phase induction motors;also the constant power control method has a better performance in comparison with a constant speed method.