Experimental verification of design techniques of permanent magnet synchronous motors for low torque ripple applications

High performance motor drive applications require smooth torque with minimum torque ripple. This paper is focused on identifying various design parameters in stator and rotor that can be used in reducing the torque ripple of a sinusoidally excited permanent magnet (PM) brushless DC (BLDC) motor. The paper investigates the sensitivity of various design parameters on torque ripple and torque linearity that must be considered at the design stage for low torque ripple applications. The torque ripple due to electromagnetic origin is considered and the effect of saturation on torque ripple and torque linearity with current is discussed. Finite element analysis along with experimental data is provided to validate the findings. Design techniques have been provided to minimize the overall torque ripple and increase the torque linearity. Tradeoff between magnetic flux per pole and electrical loading of the machine is needed for low torque ripple performance. This also provides superior torque linearity.