| Brushless DC motors (BLDC) are ever-increasingly utilized in many fields, including industrial controllers and household appliances. With its wide application in many fields, the traditional sensor control method is not applied in some application. So, sensorless control method emerges as the times require, especially Back-EMF method is more and more useful than the traditional sensor control method. But when the motor is at standstill or at a low speed, it is impossible or very difficult to get the position information from back-EMF.In this paper, based on the profound comprehension of inductance variation method, in view of the deficiency in rotor position detecting at standstill or low-speed, a new motor with obvious inductance variation on the rotor position but with little mutual inductance is designed, and a novel method named "Current Method for No Power Phase" for detecting the rotor position is proposed: A three-phase motor has six segments of an electrical cycle, let the two phases out of three are carrying currents. By detecting the currents of the third phase, we can determine the rotor position. Concretely, two Execution Plans named Complementary PWM method and Injected Testing Voltage Pulse method are proposed. Then, a mathematical model will be built and true parameters of electric machine will be used in Matlab for simulation. Finally, through experiments, the two methods will be emphatically analyzed and their features,advantages and disadvantages are compared.
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