Position Observer for Electrical Machines

A control system for an electrical motor comprising a rotor, a stator having a plurality of phase windings, and an inverter for applying voltage to the plurality of phase windings by connecting individual phase windings to a first or second voltage level, the control system configured:

• to measure a first rate of change of current in a first phase winding, of said plurality of phase windings, connected to the first voltage level;
• to measure a second rate of change of current in a second, different phase winding connected to the second voltage level;
• to measure a third rate of change of current in a third, different phase winding connected to the second voltage level;
• to calculate a difference between the first rate of change of current and the sum of the second and third rates of change of current;
• and
• to use the calculated difference to obtain data related to a position of the rotor.

A control system for an electrical motor comprising a rotor, a stator having a plurality of phase windings, and an inverter for applying varying voltages to the plurality of phase windings so as to cause rotation of the rotor, the control system configured:

• to operate the motor in a low speed regime;
• and
• while operating in the low speed regime:
• to measure the stator current in the phase windings of the stator arising from the application of stator voltage;
• to determine position of the rotor in relation to the stator;
• and
• to calculate a motor characteristic of the electrical motor from the positions of the rotor, the stator voltages and stator current, and a resistance of the phase windings.