A magnet management method of controlling a ferrite-type permanent magnet electrical machine includes receiving and/or estimating the temperature permanent magnets; determining if that temperature is below a predetermined temperature; and if so, then: selectively heating the magnets in order to prevent demagnetization and/or derating the machine. A similar method provides for controlling magnetization level by analyzing flux or magnetization level. Controllers that employ various methods are disclosed. The present invention has been described in terms of specific embodiment(s), and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims.

Provided is a motor controller that can estimate the magnetic flux of a magnet without changing a current of an electric motor. A motor controller 1 includes a current detecting unit 15 that detects a current of an electric motor 5, a current stability determining unit 10 that determines whether or not a current detected by the current detecting unit 15 is stable, and a magnetic flux calculating unit (filters 8a to 8e, a current conversion unit 4b, a resistance calculating unit 9, a magnet magnetic flux estimating unit 11) that based on a determination made by the current stability determining unit 10 as to current stability, calculates the magnetic flux of a magnet of the electric motor 5, according to a voltage equation in a rotating coordinate system, to output the calculated magnet flux. The motor controller 1 further includes a control voltage output unit (a map 2, voltage instruction units 3a and 3b, a first three-phase conversion unit 4a) that outputs a control voltage to the electric motor 5, based on the magnetic flux of the magnet calculated by the magnetic flux calculating unit and on a torque instruction value.

A temperature determination method for magnet temperatures on magnets of electric motors has a test mode. A first voltage is applied to a test winding of a test motor with test magnets for impressing a first voltage-time area at first angles of a test motor rotating field. The test magnets are subject to a predefined magnet temperature. First current values are ascertained at the first angles and stored based on the predefined magnet temperature. In a normal mode, a second voltage is applied to a motor winding of an operations motor with motor magnets for impressing a second voltage-time area at second angles of a motor rotating field. The motor magnets have an operation-dependent magnet temperature. Second current values are determined at the second angles and stored based on the operation-dependent magnet temperature. The operation-dependent magnet temperature is determined by comparing a second current value with a first current value.

A motor drive device drives a motor including a magnet. The motor drive device includes a sensor to detect a current flowing through the motor, and a control unit to calculate an estimated temperature of the magnet. The control unit reduces the current if an operating condition of the motor satisfies a predetermined operating condition, and the current exceeds a corresponding threshold. The corresponding threshold is a threshold corresponding to the estimated temperature of the magnet in threshold information in which a plurality of temperatures of the magnet and a plurality of thresholds are associated with each other. The control unit reduces the current if the operating condition of the motor does not satisfy the predetermined operating condition, and the current exceeds a fixed threshold. The fixed threshold is a threshold corresponding to a preset temperature of the magnet in the threshold information.

A propulsion system includes a propulsion device and a flight control device. The propulsion device includes a motor. The motor includes a rotor magnet. The flight control device acquires a motor temperature. The flight control device acquires a motor current. The flight control device performs management processing for managing demagnetization of the rotor magnet using driving information such as the motor temperature and the motor current. The management processing includes processing of determining whether a state of the motor is in an abnormal region, a demagnetization region, or a general region. In the management processing, the motor current is limited according to which region the state of the motor is in.

Control of a motor with a stator and permanent magnets is described. The method includes providing input data, calculating a calculated magnetic flux of the motor, the calculated magnetic flux being calculated based on an initial voltage and an actual current, currently applied to the motor, computing a new current reference based on the calculated magnetic flux and the input data, and applying a new voltage to the motor based on the new current reference so that the actual current applied to the motor reaches the new current reference.