Technical Reports

A Study of Linear Induction Motor Characteristics: The Oberretl Model

  • 01
  • May
  • 1975
AUTHOR: Federal Railroad Administration
KEYWORDS: A Study of Linear Induction Motor Characteristics; The Oberretl Model; Linear Induction Motor; LIM Propulsion Characteristics; End-Effect
ABSTRACT: The Oberretl theory of the double-sided linear induction motor is examined, starting with the idealized model and accompanying assumptions, and ending with relations for predicted thrust, airgap power, and motor efficiency. The effect of varying the maximum transverse harmonic order on the transverse primary current density and airgap flux density is considered. The Oberretl theory is seen to lead to excessively large flux densities in the regions adjacent to the primary which results in an overestimate of the normal attractive forces at small motor slip frequencies. A comparison of the LIM forces predicted by the Oberretl and Elliott models is given for the TLRV and LIMRV LIMs. The Oberretl theory gives thrust in good agreement with those of Elliott for the LIMRV; for the TLRV, the Oberretl theory predicts thrust about 20 percent greater than those predicted by Elliott. The corresponding normal forces predicted by the Oberretl theory were approximately three times greater than those predicted by Elliott. A computer program developed as part of this study program is given in the appendix. It requires computing times of the order of 50 seconds for typical runs consisting of ten case points.