A control device estimates a flow rate and an effective height difference of a fluid machine based on a characteristic detectable with regard to a rotating electrical machine and correlating with the flow rate and the effective height difference of the fluid machine. A total flow rate in a pipe system is estimated based on these values estimated by the control device and a flow resistance characteristic line, and cooperative control of the fluid machine and the flow rate control valve is performed such that the estimated value of the total flow rate becomes close to a target flow rate of the total flow rate in the pipe system.

A method of monitoring the mechanical condition of a passenger door on a public transit vehicle wherein the door operator is a brushed direct current electrical motor and comprises the steps of: repeatedly recording a profile of the motor current vs. time following initiation of opening or closing of the door; based on previously recorded profiles establishing acceptable ranges of motor current for times following initiation of opening or closing the door; and comparing an instant motor current profile to the acceptable ranges and indicating a potential fault condition if the motor current is outside the acceptable ranges.

A PWM control part rotationally drives a motor based on a PWM control value. A rotation speed control part controls a rotation speed of the motor. A rotation angle detection part detects a rotation angle of the motor. A reference position learning part controls the motor to rotate at a constant rotation speed until a detent plate stops at a limit position of a movable range and learns a reference position of the motor. A current detection circuit detects a current value corresponding to a driving current. A current limitation part limits a current supplied to the motor. A PWM control value limitation part controls the PMW control value to be equal to or smaller than a PWM limitation value, which is a predetermined value. A relation check part checks whether a relation between a current value detected by the current detection circuit and the PWM control value is inappropriate.

Provided is a method for controlling a wind power installation, the wind power installation having a generator for the generation of electric current, the generator having an air gap with a variable air gap thickness, the wind power installation being controlled in a part load range by means of a control regulation, the wind power installation being controlled in a manner which is dependent on the air gap thickness, the control regulation being selected or set in a manner which is dependent on the air gap width.

A method for controlling a variable speed drive arranged for powering an electric motor, the variable speed drive comprising a power part and a control part. The method comprises a preliminary phase of storing a set of predetermined levels of flux of the electric motor. Then, during a current phase, the method comprises selecting a level of flux from among the set of predetermined levels of flux and controlling the power part of the variable speed drive based on the selected level of flux as reference value.

The electric motor control device includes a rotation angle correction amount calculation unit that, based on a rotation angle signal for an alternating current electric motor output from an angle sensor and a current detection signal for the alternating current electric motor output from a detector, calculates a rotation angle correction amount to correct a rotation angle error between the rotation angle signal and a magnetic pole position of the alternating current electric motor, wherein the rotation angle correction amount calculation unit, based on a current detection signal when a short circuit is caused between winding terminals of the alternating current electric motor, calculates at least either one rotation angle correction amount of a direct current component rotation angle correction amount and an alternating current component rotation angle correction amount.

The present invention provides an acceleration method for V/f controlled induction motor in flux-weakening region, which comprises: acquiring no-load magnetizing current I.sub.m of the induction motor at current stator frequency; selecting a smaller one of 0.5.Math.I.sub.m(1/σ+1) and (I.sub.m.sup.2+σ)/(I.sub.m+σI.sub.m) as magnetizing current set point, in which σ is an estimated total leakage inductance coefficient; getting an error signal by subtracting the magnetizing current of the induction motor from the magnetizing current set point; determining the stator frequency for the next control period according to the error signal which is provided as a controlling variable of negative feedback. The acceleration method of the present invention can provide the maximum output torque in flux-weakening region and has a larger tolerance for the error of the estimated leakage inductance.

A rotary current machine system and method for controlling an electric rotary current machine, in particular an induction machine, having a rotor, a stator and at least two phase windings is disclosed. At least one electrical signal, in particular a voltage signal, is applied to at least one phase winding, preferably all phase windings, of the rotary current machine, and the current waveform in the at least one phase winding is measured. An intermodulation signal component, induced in the rotary current machine by slotting effects and magnetic saturation effects, which is determined from the current waveform measured in the at least one phase winding, is used for controlling the rotary current machine.

The invention relates to a method for controlling an inverter which is electrically connected to an electric motor, having the following steps: defining a modulated voltage (S1) for the inverter, said voltage being based on a first switching frequency, for operating the electric motor with a current, wherein the current has an electric frequency; determining the electric frequency (S2); changing the first switching frequency (S4) on which the modulated voltage is based to a second switching frequency if a value pair consisting of electric frequency and first switching frequency, or a value pair consisting of electric frequency and a sideband of the first switching frequency, is within at least one defined disturbance range (S3).

A method for categorizing performance of a PMSM coupled to a drive shaft, and powered by a battery via an inverter. The method comprising: decoupling the PMSM from drive shaft; performing a first retardation test to measure the flux linkage of the permanent magnets, PM flux, in the PMSM; performing a second retardation test in which the inverter is disconnected, to measure the no-load power losses of the PMSM; correlating the PM flux with the no-load power losses in a health parameter of the PMSM, and comparing the health parameter with reference data of known health parameters of a population of PMSMs; categorizing the performance of the PMSM based on the compared health parameter.