Provided is a method of assessing rotor temperature during operation of a permanent magnet synchronous machine, including a stator having at least one winding set, the method including: providing reference flux linkage values for different rotor and stator temperature values and current values of an operating winding set; measuring an actual rotor temperature value; measuring an actual stator temperature value; measuring an actual current value of an operating winding set; deriving and storing reference flux linkage values for a given set of operating conditions, in particular, by means of a reference run; deriving a reference flux linkage value (for the measured actual rotor and stator temperature values and the measured actual current value of the operating winding set) using the flux model; obtaining a voltage value; deriving an estimated flux linkage value; deriving a rotor temperature offset; and assessing the rotor temperature based on the rotor temperature offset.

To provide a motor control method ensuring that dragging loss at the time of high rotation can be reduced.

A motor control method, wherein a composite permanent magnet has a core part and a shell part, the Curie temperature of one of the core part and the shell part is T.sub.c1 K, and the Curie temperature of another is T.sub.c2 K, and wherein when the magnitude of the reluctance torque is equal to or greater than the magnitude of the magnet torque, the temperature of the composite permanent magnet is set at T.sub.s K that is (T.sub.c1100) K or higher and lower than T.sub.c2 K and when the magnitude of the reluctance torque is less than the magnitude of the magnetic torque, the temperature of the composite permanent magnet is set at lower than the temperature T.sub.s K or T.sub.c1 K, whichever is lower.

A motor includes a magnet and a coil. 2=[{(Br2Br1)/Br1}/(T2T1)]1000.10 and 3=[{(Br3Br1)/Br1}/(T3T1)]1000.12 are satisfied. In the magnet, Br1 (mT) is a residual magnetic flux density at T1 ( C.), Br2 (mT) is a residual magnetic flux density at T2 ( C.), and Br3 (mT) is a residual magnetic flux density at T3 ( C.), and 2 (%/ C.) is a temperature coefficient at a target temperature of T2 ( C.) with respect to a reference temperature of T1 ( C.), and 3 (%/ C.) is a temperature coefficient at a target temperature of T3 ( C.) with respect to a reference temperature of T1 ( C.) in conditions of T1=23, T2=60, and T3=180.

A drive device for a rotating electric machine having a stator including a stator winding and a rotor including a permanent magnet includes: a power conversion circuit which outputs a phase current to the stator winding; and a control unit which controls the power conversion circuit. If a phase voltage crest value relative to a voltage of DC power is defined as a modulation factor, the control unit decreases a current amplitude and a current advance angle of the phase current if a temperature of the permanent magnet is higher than a predetermined first threshold-value temperature and the modulation factor is larger than a predetermined threshold value, and increases the current amplitude and the current advance angle of the phase current if the temperature of the permanent magnet is higher than the first threshold-value temperature and the modulation factor is smaller than the threshold value.

A permanent-magnet electric motor includes: a rotor; and a rotational-position detection sensor configured to detect a rotational position of the rotor. The rotor includes: a rotating shaft; an annular ferrite magnet disposed on an outer circumferential surface of the rotating shaft; and a rare-earth magnet disposed on an outer circumferential surface of the ferrite magnet, and a length from a center of the ferrite magnet in an axial direction of the ferrite magnet to an end face of the ferrite magnet on a side of the rotational-position detection sensor in the axial direction of the ferrite magnet is longer than a length from a center of the rare-earth magnet in an axial direction of the rare-earth magnet to an end face of the rare-earth magnet on a side of the rotational-position detection sensor in the axial direction of the rare-earth magnet.

A control system for monitoring a motor and wheel drive gearbox of an irrigation system drive train. The control system includes a motor sensor for sensing an operating state of the motor and a gearbox sensor for sensing an operating state of the wheel drive gearbox. If the motor operating state exceeds a motor operating state threshold or changes too quickly, or if the wheel drive gearbox operating state exceeds a wheel drive gearbox operating state threshold or changes too quickly, the control system operates the drive train at a reduced capacity or in a modified mode such that the operating state is not exceeded or does not change too quickly.

A motor control device having a motor temperature sensor for detecting a magnet temperature of the motor, a magnet magnetic flux calculation section that calculates a magnet magnetic flux of the motor corresponding to the magnet temperature of the motor, a current combination candidate calculating section that calculates a d-q axis current combination candidate that minimizes the input current of the inverter within a voltage limit ellipse determined by a value that can be output by a voltage of a power supply of the motor, and a d-q axis current search section that searches the d-q axis current that minimizes the input current of the inverter within the range of the combination candidate of the d-q axis currents when the d-q axis current of the motor moves on a voltage limiting ellipse by automatic weakening flux control.

Given a first intersection point of the surface of a rotor and a straight line that joins a central point of a permanent magnet on a stator side and a tooth tip section closest to the central point of the permanent magnet on the stator side, a flange is formed outward of an arc having, as the radius thereof, a distance from a second intersection point of the inner peripheral face of the stator and a straight line that joins the rotation axis of the rotor and the first intersection point, up to the tooth tip section.

A power conversion device control system includes a power conversion device configured to supply electric power to a rotary electric machine, and a control device configured to control the power conversion device, wherein the control device controls the power conversion device through synchronous control in which a carrier frequency of the power conversion device is proportional to a rotational speed of the rotary electric machine when a temperature of a permanent magnet provided in the rotary electric machine is higher than a predetermined threshold value, and controls the power conversion device through non-synchronous control in which a carrier frequency of the power conversion device is not proportional to a rotational speed of the rotary electric machine when a temperature of the permanent magnet is the predetermined threshold value or less.

Provided are: a synchronous machine having permanent magnets as a field system; a stress estimator that estimates stress acting on the permanent magnets; and a first magnet temperature corrector that calculates an amount of demagnetization due to stress of armature interlinkage magnetic flux on the basis of the estimated stress, estimates an amount of demagnetization due to stress of the armature interlinkage magnetic flux on the basis of the rotor position of the synchronous machine, a current command and a voltage command, and the amount of demagnetization due to stress of the armature interlinkage magnetic flux; and outputs a permanent magnet temperature estimated value after correction, having factored therein the amount of demagnetization due to stress of the armature interlinkage magnetic flux from the estimated armature interlinkage magnetic flux.