Development of a transverse flux sensor

Rotary Variable Differential Transformer (RVDT) sensors are used for industrial applications. They operate without mechanical or electrical contact. Frictionless operation gives a long mechanical life and high reliability. RVDT are appreciated for their high level of linearity and sensitivity due to their differential structure. The sensor shown here derives from a classic RVDT and is based on a differential rotating transformer. The originality of the studied sensor lies in the transverse flux design, which enhanced linearity on most of the 180° stroke (error is less than 0.1% on a 160° stroke). However, this transverse flux circulation has uncommon features for an electrotechnical system due to flux paths, which are not enclosed in radial planes. This study aims to enhance sensor performances and ease of manufacture.The working frequency is relatively high (few kilo-Hertz). An experimental process as been set up leading to the precise identification of each phenomenon: leakage flux, circular induced currents, Eddy currents skin effect and local saturations. The results presented in this paper are then issued from series of tests and measures in which cases are separately studied.The study aims to understand then to simulate the internal functioning of the sensor. This approach is analysing experimental and theoretical aspects. Measurements are made on experimental sensor and are compared to numerical results. A 3D-finite element analysis is combined with an analytical model based on a reluctance network taking account of most magnetic flux paths. The processed study has allowed identification of most sensor weaknesses and has led to improvements for such type of sensor.