Magnet Temperature Estimation in Surface PM Machines During Six-Step Operation

• Published in: IEEE transactions on industry applications Vol. 48; no. 6; pp. 2353 - 2361
• Main Authors: Reigosa, D. D., Briz, F., Degner, M. W., Garcia, P., Guerrero, J. M.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.11.2012; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Electric potential; Estimating; Estimation; Frequency measurement; Harmonic analysis; Harmonics; Magnet temperature estimation; Monitoring; permanent-magnet (PM) synchronous machines (PMSMs); Risk; Rotors; six steps; Stators; Temperature measurement; Torque; Voltage; Voltage measurement
• ISSN: 0093-9994; 1939-9367
• DOI: 10.1109/TIA.2012.2227097

This paper presents a method for estimating the magnet temperature in surface permanent-magnet (PM) synchronous machines during six-step operation. Six-step operation allows the maximum available dc-bus voltage to be applied to a machine, which maximizes its torque and speed range. This can be of importance in electric traction applications, including railway as well as electric and hybrid electric vehicles. However, six-step operation produces current harmonics that induce additional losses in the PMs and can therefore increase their temperature. An increase of magnet temperature can result in a reduced torque capability and eventually in a risk of demagnetization if excessive values are reached, with real-time rotor magnet temperature monitoring being therefore advisable. Six-step operation provides opportunities for rotor temperature monitoring from the electrical terminal variables (voltages and currents) of the motor. To achieve this goal, the rotor high-frequency resistance is measured using the harmonic voltages and currents due to six-step operation, from which the magnet temperature can be estimated.