Airgap Flux Search Coil-based Estimation of Permanent Magnet Temperature for Thermal Protection of PMSMs
Hyeonjun Lee, Jigyun Jeong, Marcos Orviz Zapico, Sang Bin Lee, David Reigosa, Fernando Briz del Blanco
Abstract
Airgap flux monitoring, commonly used in wound field synchronous generators, has recently received a lot of attention for detecting faults in permanent magnet synchronous motors (PMSM), since a low-cost airgap search coil can provide reliable detection of motor faults. In this paper, the feasibility of using the airgap search coil for estimating the temperature of the PM, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T<sub>PM</sub></i> , for thermal protection is evaluated for the first time. The model- or signal injection-based methods proposed for TPM estimation can provide satisfactory estimates of the average <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T<sub>PM</sub></i> for thermal protection. However, the complexity in the compensation required for non-ideal effects and/or the negative impact of high frequency signal injection can limit their practical use. The new <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T<sub>PM</sub></i> estimation method based on the airgap search coil voltage measurement proposed in this paper does not require compensation for resistance variation or inverter non-linearity, or injection of high-frequency signals. In addition, it can provide detection of rotor faults, and thermal protection based on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T<sub>PM</sub></i> estimate of the hottest PM since individual PMs can be monitored. Experimental results on a 2.2 kW IPMSM verify the claims and show that the existing methods can be simplified with the proposed method.