JPS57201870A - Magnetic flux detector for induction motor - Google Patents

Abstract

PURPOSE:To eliminate an error, by preventing the missing of an operation magnetic flux at zero frequency and setting an integrator as a specified incomplete integrator, through the addition of a voltage corresponding to an excitation command current newly to a secondary effective voltage of conventional system. CONSTITUTION:A step introducing an arithmetic secondary effective voltage E2 from a detected value V1 at a terminal voltage is the same as that of conventional methods and a value adding a voltage corresponding to an exciting reference current to the E2 is denated as E'2. Thus, a relation of proportion is established between an actual exciting current im and an exciting command current Im at a start or steady state. Thus, the constant of an incomplete integrator 22 is denoted as a specific value (Km/(1+pTm) (where p is a differntial operator), and the time constant Tm is denoted as a value of (secondary magnetic flux/voltage corresponding to exciting command current), then an integration value phi'2 of the voltage E'2 is expressed as phi'2=KmKvRMim (where; Km and Kv are constants), and a value proportional to the exciting current im can be operated at zero frequency independently of the constant Km of the integrator 22.