Abstract: A method to control a switched reluctance motor (SRM) with a first phase (1) and a second phase (2) comprises: aligning the rotor with the second phase (2); at a first time point (t1), energizing the first phase (1) with a phase voltage that is substantially constant; monitoring an increase of the phase current (I1) in the first phase (1) until the phase current reaches a maximum (302); monitoring a decrease (303) of the first current (I1) until at a second time point (t2) the phase current (I1) reaches a minimum (304) and starts to increase again (305); de-energizing the first phase (1) at a third time point (t3) that follows the second time point at (t2) at a predetermined time interval; and repeating energizing, monitoring and de-energizing for the second phase (2) instead of the first phase (1).

Abstract: A controller (40) which estimates the coil resistance (R) of an electric motor (10), receives representations of a voltage (u(t)) across a stator coil (11) and of a current (i(t)) through the coil (11). At first, the controller (40) estimates the magnetic flux (&PSgr;E(t2)) in the coil by integrating the difference between u(t) and the product between the current with a preliminary resistance (R) over a predetermined time interval (t1, t2) in which the coil (11) is energized. Second, the controller (40) calculates a resistance error (&Dgr;R) using a known actual flux value &PSgr;A(t2) at the end (t2) of the time interval, the previously estimated magnetic flux &PSgr;E(t2) and the integral of the current over the time interval. Third, the calculator derives the coil resistance (R) from the preliminary resistance (R) and the resistance error (&Dgr;R).

Abstract: In a method for controlling an electric motor the stator voltage frequency of the motor is determined by adding the optimal slip frequency of the motor and the desired rotational frequency of the rotor. The magnitude of the stator voltage is determined by subtracting the actual rotational frequency and the desired rotational frequency of the rotor. The desired stator frequency and magnitude are inputted into a pulse width modulation unit which controls an inverter to supply the appropriate voltages to the motor. The operation of the motor with optimal slip has the advantage that the efficiency is optimal independent of the load.