A technique to minimize the effect of current harmonics in a brushless DC motor drive

Brushless motors offer several advantages over their brushed counterparts, including more torque per weight, increased efficiency, increased reliability, reduced noise, longer lifetime, elimination of ionizing sparks from the commutator, and overall reduction of electromagnetic interference (EMI). This paper describes the influence of different harmonics currents in the motor drive application. A variety of active and passive approaches can be adopted to reduce harmonics in systems that rely on precision motion control. For applications ranging from medical diagnostic to office automation equipment, the need to suppress conducted and radiated noise is critical, especially in light of increasingly stringent electromagnetic compatibility (EMC) requirements. The challenges are to maintain system integrity and motor performance without adding significant cost or weight to a subassembly. This paper adopts active approach to reduce the effects of harmonics by introducing active line filter with PFC circuit at the input of power converter. Controller deployed use of differential signals. This improves noise immunity by processing a signal that is the algebraic difference of two complementary signals at the input. Experimental results are presented in this paper. Set-up consists of BLDC motor, IGBT based inverter, TI DSP based motor controller, power quality analyzer, and current probes.