Automated monitoring of magnet quality for permanent magnet synchronous motors at standstill

Demagnetization of permanent magnets (PM) used in synchronous motors (SM) can occur due to a combination of thermal, electrical, and/or environmental operating stresses. Since PM demagnetization results in degradation of motor performance, efficiency, and reliability, it is important to monitor the quality of PMs regularly. However, there are many limitations to the off-line and on-line methods currently used for magnet quality assessment. In this paper, a new inverter-embedded technique for automated monitoring of magnet quality for permanent magnet synchronous motors (PMSM) that overcomes the limitations of existing techniques is proposed. The main concept is to use the inverter to perform a standstill test whenever the motor is stopped to detect local or uniform PM demagnetization. The machine is excited with a pulsating field at different angular positions, and the change in the current peaks caused by the change in the degree of magnetic saturation due to demagnetization is observed. An experimental study on a 10hp PMSM verifies that local and uniform PM demagnetization can be detected with high sensitivity.

[1]  R. Spee,et al.  Remedial strategies for brushless DC drive failures , 1988, Conference Record of the 1988 IEEE Industry Applications Society Annual Meeting.

[2]  Thomas M. Jahns,et al.  Analysis of Rotor Core Eddy-Current Losses in Interior Permanent Magnet Synchronous Machines , 2008, 2008 IEEE Industry Applications Society Annual Meeting.

[3]  Tomy Sebastian,et al.  Temperature effects on torque production and efficiency of PM motors using NdFeB magnets , 1993, Conference Record of the 1993 IEEE Industry Applications Conference Twenty-Eighth IAS Annual Meeting.

[4]  S. Ostlund,et al.  Sensorless rotor-position detection from zero to rated speed for an integrated PM synchronous motor drive , 1996 .

[5]  T.G. Habetler,et al.  Detecting Rotor Faults in Low Power Permanent Magnet Synchronous Machines , 2007, IEEE Transactions on Power Electronics.

[6]  A. Wijenayake,et al.  Initial rotor angle detection of a nonsalient pole permanent magnet synchronous machine , 1997, IAS '97. Conference Record of the 1997 IEEE Industry Applications Conference Thirty-Second IAS Annual Meeting.

[7]  T.G. Habetler,et al.  Dynamic Eccentricity and Demagnetized Rotor Magnet Detection in Trapezoidal Flux (Brushless DC) Motors Operating Under Different Load Conditions , 2007, IEEE Transactions on Power Electronics.

[8]  R. D. Lorenz,et al.  Rotor position and velocity estimation for a salient-pole permanent magnet synchronous machine at standstill and high speeds , 1998 .

[9]  J. Rosero,et al.  Demagnetization fault detection by means of Hilbert Huang transform of the stator current decomposition in PMSM , 2008, 2008 IEEE International Symposium on Industrial Electronics.

[10]  H. Man,et al.  Magnetic And Corrosion Characteristics Of NdFeB Maget With Various Surface Coatings , 1997, 1997 IEEE International Magnetics Conference (INTERMAG'97).

[11]  Oliver Gutfleisch,et al.  Grain growth effects on the corrosion behavior of nanocrystalline NdFeB magnets , 2002 .

[12]  J.H. Lang,et al.  Monitoring the thermal condition of permanent-magnet synchronous motors , 1991, Conference Record of the 1991 IEEE Industry Applications Society Annual Meeting.

[13]  Ju Lee,et al.  The Shape Design of Permanent Magnet for Permanent Magnet Synchronous Motor Considering Partial Demagnetization , 2006, IEEE Transactions on Magnetics.

[14]  Hamid A. Toliyat,et al.  Handbook of Electric Motors , 2004 .

[15]  S. K. Pal.  Direct drive high energy permanent magnet brush and brushless DC motors for robotic applications , 1991 .

[16]  Nobuyuki Matsui,et al.  A novel starting method of sensorless salient-pole brushless motor , 1994, Proceedings of 1994 IEEE Industry Applications Society Annual Meeting.

[17]  E. Furlani.  Permanent Magnet and Electromechanical Devices: Materials, Analysis, and Applications , 2001 .

[18]  Bimal K. Bose,et al.  Investigation of fault modes of voltage-fed inverter system for induction motor drive , 1992, Conference Record of the 1992 IEEE Industry Applications Society Annual Meeting.

[19]  Shin-ichi Kondo,et al.  Armature current locus based estimation method of rotor position of permanent magnet synchronous motor without mechanical sensor , 1995, IAS '95. Conference Record of the 1995 IEEE Industry Applications Conference Thirtieth IAS Annual Meeting.

[20]  Ji-Yoon Yoo,et al.  Condition Monitoring of DC-Link Electrolytic Capacitors in Adjustable-Speed Drives , 2007, IEEE Transactions on Industry Applications.

[21]  A. G. Jack,et al.  Predicting and Preventing Demagnetisation in Permanent Magnet Motor Drives , 2006 .

[22]  Timothy J. E. Miller,et al.  Design of Brushless Permanent-Magnet Motors , 1994 .