P5.5 - High Precision and Simple Analog Through-Shaft Magnetic Sensors for the Control of Electric Drives

SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
Proceedings SENSOR 2011
P5 - Magnetic
M. Delbaere, G. Masson, T. Dorge, D. Frachon, S. Biwersi - Moving Magnet Technologies S. A., Besançon (France)
786 - 791


Many synchronous electric motors require a very accurate position sensor compatible with a sinusoidal control that will enable a very efficient and smooth operation enhancing the comfort by limiting vibrations. This feature is for example important for large power drives for electric or hybrid electric vehicles where the electric machine is located in between the combustion engine and the transmission requiring a very large through shaft design. More generally, these sensors need to keep a simple and robust design and a restricted number of parts as they are submitted to high vibration levels, a wide temperature range and speeds of 15 krpm.
In order to answer such requirements, MMT has developed a magnetic sensor principle which offers a competitive alternative to the conventional inductive resolver type sensors. The basic of this solution is a through shaft angular position sensor using one or two probes of Hall effect type or GMR type which measure the angle of the magnetic field generated by a magnet with a specific N pole pairs magnetization, to meet very demanding accuracy requirements and able to deal with some external magnetic perturbations. The number of pole pairs can be equal to the number of motor pole pairs in order to get an absolute position over the electric period or N is equal to 1 in case of absolute position over 360°.
The paper deals with this sensor principle applied to a six pole pairs machine showing that the challenge to meet less than +/-1° of electric error on a 6 pole pairs magnet with inner diameter in the range of 100 mm was took up.
Key features like effects of high speed rotation on the sensor accuracy and mechanical tolerances will be discussed thanks to prototype results.