Method for controlling a permanent magnet motor

A method of controlling operation of a permanent magnet motor, comprising:

• applying to the motor, phase currents which are substantially in phase with corresponding electromotive forces of the motor when a first mode of operation is selected;
• applying to the motor, phase currents which are substantially in phase with corresponding electromotive forces of the motor and substantially sinusoidal when a second mode of operation is selected;
• selecting from said first mode of operation and said second mode of operation based on at least one of a signal indicative of a parameter of the motor and a command signal wherein the first and second modes of operation are constant torque modes, and wherein the second mode of operation is selected from the first mode of operation when a load current exceeds a preset value;
• and
• wherein said permanent magnet motor comprises a permanent magnet brushless direct current motor having a trapezoidal distribution of magnetic field in an airgap thereof.

A permansent magnet motor control system for an electric vehicle, comprising:

• a permanent magnet motor associated with the electric vehicle;
• a battery associated with the electric vehicle;
• an inverter receptive to direct current signals from the battery for providing phase currents to the motor;
• and
• a controller for selecting a mode of operation from first, second and third modes of operation, wherein the first and second modes of operation are constant torque modes and the third mode of operation is a field weakening mode, and for producing control signals, based on at least one of a signal indicative of a parameter of the motor and a command signal, the inverter in response to the control signals providing phase currents which are substantially in phase with corresponding electromotive forces of the motor when the first mode of operation is selected, are sinusoidal and substantially in phase with corresponding electromotive forces of the motor when the second mode of operation is selected wherein the second mode of operation is selected from the first mode of operation when a load current exceeds a preset value, and are substantially out of phase with corresponding electromotive forces of the motor when the third mode of operation is selected;
• wherein said permanent magnet motor comprises a permanent magnet brushless direct current motor having a trapezoidal distribution of magnetic field in an airgap thereof.

A permanent magnet motor control system for an electric vehicle, comprising:

• a permanent magnet motor associated with the electric vehicle;
• a battery associated with the electric vehicle;
• a controller for selecting a mode of operation from a first mode of operation and a second mode of operation, the first and second modes of operation being constant torque modes, said controller producing control signals based on at least one of a signal indicative of a parameter of the motor and a command signal;
• and
• an inverter receptive to direct current signals from the battery for providing phase currents to the motor, said inverter, in response to the control signals, providing phase currents which are substantially in phase with corresponding electromotive forces of the motor when the first mode of operation is selected and are substantially sinusoidal and substantially in phase with corresponding electromotive forces of the motor when the second mode of operation is selected,
• wherein the second mode of operation is selected from the first mode of operation when a load current exceeds a preset value;
• and
• wherein said permanent magnet motor comprises a permanent magnet brushless direct current motor having a trapezoidal distribution of magnetic field in an airgap thereof.