Patent ID: 7800323
Filing Date: 2010-09-21
Classification: H02P

Abstract:
1. Method for estimating the rotational speed ω of an electric motor when it is freewheeling, the method being carried out in a variable speed drive for controlling the motor by generating reference alternating voltages Va, Vb, characterised in that the method includes: a step for measuring a flux current Id and a torque current Iq of the motor in an orthogonal two-phase marker d,q, a step for determining said reference alternating voltages Va, Vb, by carrying out a current regulation on the basis of said measured flux and torque currents Id and Iq, and on the basis of a zero reference current Idref and a zero reference current Iqref in said marker d,q, a calculation step wherein the rotational speed ω is calculated by evaluating an angle of rotation of a voltage vector, the components of which are said reference alternating voltages Va, Vb in a fixed orthogonal two-phase marker a,b, the calculation step using a PLL circuit which is inputted with the reference alternating voltages Va, Vb and which outputs the rotational speed ω.