A system and method for controlling an electric machine via an inverter comprises an speed estimator that is configured to estimate a rotor speed of an electric motor to determine whether to control the inverter to operate the electric motor in a first mode or a second mode. For example, the first mode comprises a current-frequency control mode and the second mode comprises a back electromagnetic force (BEMF) mode. An electronic data processor or controller is configured to determine a first (current) command associated with a first mode of operating the electric motor, if the estimated rotor speed is a less than a speed threshold. The electronic data processor or controller is configured to determine a second (current) command associated with a second mode of operating the electric motor if the estimated rotor speed is equal to or greater than the speed threshold.

A system and method for controlling an electric machine via an inverter comprises an speed estimator that is configured to estimate a rotor speed of an electric motor to determine whether to control the inverter to operate the electric motor in a first mode or a second mode. For example, the first mode comprises a current-frequency control mode and the second mode comprises a back electromagnetic force (BEMF) mode. An electronic data processor or controller is configured to determine a first (current) command associated with a first mode of operating the electric motor, if the estimated rotor speed is a less than a speed threshold. The electronic data processor or controller is configured to determine a second (current) command associated with a second mode of operating the electric motor if the estimated rotor speed is equal to or greater than the speed threshold.

A motor drive control device includes a drive circuit configured to drive a motor with a drive control signal for driving the motor, and a control circuit configured to perform a vector control arithmetic operation based on a detection result of drive currents of coils of the motor, to generate the drive control signal and supply the drive control signal to the drive circuit. When generating the drive control signal, the control circuit estimates a rotation angle of a rotor of the motor and a rotation speed of the rotor with a q-axis current value of a two-phase rotating coordinate system calculated with a detection result of the drive current, and a q-axis voltage command value of the two-phase rotating coordinate system, by using a linear Kalman filter including a prediction step and an update step, using a stationary Kalman filter with the prediction step expressed linearly and time-invariantly.

A motor drive control device includes a drive circuit configured to drive a motor with a drive control signal for driving the motor, and a control circuit configured to perform a vector control arithmetic operation based on a detection result of drive currents of coils of the motor, to generate the drive control signal and supply the drive control signal to the drive circuit. When generating the drive control signal, the control circuit estimates a rotation angle of a rotor of the motor and a rotation speed of the rotor with a q-axis current value of a two-phase rotating coordinate system calculated with a detection result of the drive current, and a q-axis voltage command value of the two-phase rotating coordinate system, by using a linear Kalman filter including a prediction step and an update step, using a stationary Kalman filter with the prediction step expressed linearly and time-invariantly.

A closed-loop method of starting a permanent magnet synchronous motor comprises driving the rotor by energizing stator windings using motor control signals based on an initial standstill rotor angle. Periodically estimating values of rotor flux linkage magnitude and/or angle based on back-electromotive force (emf) induced in the stator windings by the rotating rotor. The estimated values of rotor flux linkage magnitude are used to estimate respective new rotor angles which are used to generate updated motor control signals to drive the rotor. Control of the motor is switched-over to a closed-loop synchronous operation motor control algorithm in response to any one or any combination of the following conditions: at a predetermined period of time from initiation of the closed-loop start-up method; or upon determination that the rotor has reached a minimum operating speed; or upon determination that the estimated value of rotor flux linkage magnitude reaches or exceeds a threshold value.

Described is a method of aligning a rotor of a polyphase synchronous motor having a permanent magnet rotor to a predetermined, selected, or specified rotor angle. The method comprises sensing or measuring the stator winding voltages/currents during synchronous operation of the motor. Based on the sensed or measured stator winding voltages/currents, a synchronously rotating reference frame vector voltage (V.sub.9) in the q-axis is determined as a product of stator winding resistance (R.sub.s) and stator winding current (i.sub.q) in the q-axis. Corresponding polyphase drive voltages for the synchronous motor for the predetermined, selected, or specified rotor angle (θ) are determined from the synchronously rotating reference frame vector voltage (V.sub.q). The polyphase drive voltages are applied to align the rotor on stopping at said predetermined, selected, or specified rotor angle (θ), The polyphase drive voltages are applied by suitable PWM drive signals.

Described is a method of determining an initial speed of a synchronous motor having a permanent magnet rotor. The method comprises controlling said motor to cause the rotor to rotate or observing that the rotor is rotating. The method includes sensing stator winding currents and transforming the sensed stator winding currents into a two-dimensional (2D) coordinate system using an alpha-beta (α-β) transformation. The rotor angle θ is determined from an arc tangent (Atan) of the ratio of the current in the α-axis to the current in the β-axis. The initial motor speed ω is determined from the determined rotor angle θ.

A vector control system is used to control a vapor compression circuit. The vector control system may monitor the vapor compression circuit and adjust the speed of one or more motors to increase efficiency of the system by taking into account the torque forces placed on a compressor motor.

A motor control device and a motor control method are provided. The motor control device includes a memory and a controller. During an initialization period, the controller drives a brushless DC motor to change a rotor position through a drive circuit for adjusting and obtaining a starting angle and a locked exciting current corresponding to the starting angle, and the controller stores starting-angle information corresponding to the starting angle and locked exciting-current information corresponding to the locked exciting current in the memory. After the initialization period ends, during a normal rotation period, the controller maintains the rotor position of the brushless DC motor at the starting angle with the locked exciting current through the drive circuit, until the controller activates the brushless DC motor through the drive circuit.

A motor control device and a motor control method are provided. The motor control device includes a memory and a controller. During an initialization period, the controller drives a brushless DC motor to change a rotor position through a drive circuit for adjusting and obtaining a starting angle and a locked exciting current corresponding to the starting angle, and the controller stores starting-angle information corresponding to the starting angle and locked exciting-current information corresponding to the locked exciting current in the memory. After the initialization period ends, during a normal rotation period, the controller maintains the rotor position of the brushless DC motor at the starting angle with the locked exciting current through the drive circuit, until the controller activates the brushless DC motor through the drive circuit.