Sensorless commutation controller for a poly-phase dynamoelectric machine

Apparatus for controlling commutation of a poly-phase electric motor having stator windings for each motor phase and a rotor for rotation with respect to said windings, comprising:

• power supply means for supplying voltage to the windings, said power supply means including an AC power source, means for converting AC power to power having an average DC value and a bus for applying the average power to the motor;
• commutation means for successively energizing the stator windings and including an inverter between the bus and the motor, the inverter controlling the commutation interval for each motor phase;
• means for sensing the bus current, said current having a waveshape the relative characteristics of which are a function of a commutation angle between the rotor and stator windings, the commutation angle providing an indication of whether the commutation is at an optimal angle, or lagging, or leading, and said current waveshape being distorted by ripple or transients on the supply lines;
• and,
• processor means for deriving commutation angle information from the sensing means and for controlling operation of the commutation means on the basis of the derived information to control the commutation angle so it is optimal for a particular mode in which the motor is operating, said processor means including commutation controller means and mode controller means, said commutation controller means processing the commutation angle information and a control variable which is derived from the bus current waveshape to correct for any sensed distortions caused by the ripple or transients, and said mode controller means providing reference signals to the commutation controller means based upon the mode in which the motor is operating, and the processor means providing frequency and voltage inputs to the commutation means for the inverter to control the commutation interval as a function of the sensed bus current waveshape.

A method of controlling the commutation angle in a dynamoelectric machine comprising:

• supplying a bus current to the machine;
• commutating windings of the machine by systematically energizing and de-energizing them with the current;
• sampling a resultant bus current waveshape which has characteristics that are a function of a commutation angle between a rotor of the machine and the machine phase windings, as well the effects of bus ripple or transients on a bus voltage waveshape;
• obtaining commutation angle information from the sampled current waveshape;
• and,
• controlling the commutation angle in response to the information obtained, said commutation angle control including calculating a control variable which is a function of the commutation angle and combining said calculated control variable with a value which is a function of the ripple on the waveshape and the machine's response to a transient.