Theoretical verification of the infinite constant power speed range of the brushless DC motor driven by dual mode inverter control

The differential equations that describe the operation of the brushless dc motor (BDCM) driven by dual mode inverter control (DMIC) are solved analytically. Explicit expressions for peak and rms motor current and average motor power are derived. The analysis is performed neglecting all motor loss mechanisms. The results provide a theoretical verification that the constant power speed range (CPSR) of the BDCM is infinite when driven by the DMIC. While speed sensitive motor losses limit the CPSR of any practical drive to a finite value, there is no inherent limitation imposed by the DMIC. The analytic formulas provide useful drive design guidance without requiring simulation or laboratory experimentation.