A comparison of torque capabilities of axial flux and radial flux type of brushless DC (BLDC) drives for wide speed range applications

This paper aims to evaluate capabilities of axial flux and radial flux brushless DC (AF and RF-BLDC) drives for washing machine applications (1:30 speed range). For this purpose, torque and EMF equations of the two types of motor are obtained in terms of electrical and magnetic loading and motor dimensions. Then the drives are evaluated on criteria such as efficiency, torque per unit mass and volume, torque per ampere etc. The AF-BLDC is found to have superior torque/mass ratio, however, this motor requires operation at high frequencies. Also, attention must be paid to control strategy to assure an acceptable torque/Amp ratio.