A measuring system, during a measurement process thereof, uses a phase-locked loop mechanism of a stator phase voltage and a stator phase current of a three-phase AC motor to effectively remove harmonics and to sense and obtain the amplitude effective values of the phase voltage and the phase current of the three-phase AC motor and the phase difference between the phase voltage and phase current. Therefore, the measuring apparatus is capable of quickly and accurately calculating the input power of the motor without having to measure the parameters of the motor.

A control device for an inverter has a first inverter terminal, a second inverter terminal and a plurality of bridge branches, which bridge branches each comprise a first semiconductor, a winding terminal and a second semiconductor switch. The winding terminals are connected to a winding arrangement. The control device is configured to output a control signal which enables a first bridge branch state and a second bridge branch state in the case of at least two of the bridge branches in a first operating state, wherein, in the first bridge branch state, the second semiconductor switch assigned to the bridge branch is switched on, and wherein, in the second bridge branch state, the second semiconductor switch assigned to the bridge branch is switched off. At least two of the bridge branches are occasionally simultaneously in the first bridge branch state, and a change of said at least two bridge branches into the second bridge branch state is subsequently carried out at different points in time.

Methods and systems of optimizing efficiency of a motor drive or generator are provided. The methods include measuring data corresponding to input power and output power of a motor drive or generator at a control parameter and different load values. The methods include generating a three-dimensional surface model based on the measured data. The three-dimensional surface model can estimate an efficiency of the motor drive or generator at the control parameter and at unmeasured load values. The methods can include determining optimal efficiency of the motor drive or generator at the different load values and the unmeasured load values based on the three-dimensional surface model.

A control device of an AC rotating electrical machine includes: a midpoint potential detection unit 12 that detects, for respective phases, midpoint potentials 43, 44, 45 of upper switching elements 41 and lower switching elements 42 of an inverter circuit 20; a phase current detection unit 23 that detects a phase current of each phase of an AC rotating electrical machine 3; and a CPU 11 that calculates a current estimated value Idc of DC current that is input from a DC power supply 2 to the inverter circuit 20, on the basis of the detected midpoint potential of each phase and the phase current of each phase.

A system may have a digital period divider generating an output signal that is proportional to an angle defined by a rotational input signal and an interval measurement unit determining an interval time of an interval defined by succeeding pulses of the input output signal. In an enhancement, the system may also have a missing pulse detector which is operable to compare a current interval with a parameter to determine whether a pulse is missing in the input signal.

A system may have a digital period divider generating an output signal that is proportional to an angle defined by a rotational input signal and an interval measurement unit determining an interval time of an interval defined by succeeding pulses of the input output signal. In an enhancement, the system may also have a missing pulse detector which is operable to compare a current interval with a parameter to determine whether a pulse is missing in the input signal.

A control device for an electric compressor, capable of successfully controlling a drive motor of the compressor in response to the load fluctuation having complicated frequency components even when the motor is controlled in a sensorless manner, is provided. The control device for an electric compressor includes: a repetitive control portion 5 to which a rotation speed difference between a target rotation speed of a motor which drives the compressor and the estimated rotation speed is input to perform a repetitive operation using the rotation speed difference of one preceding cycle of the compressor, thereby reducing the rotation speed difference; a pressure detecting portion 1 for the compressor; and a reset signal generation portion 4 calculating a timing of one rotation of the compressor by counting the number of predetermined parts of load fluctuations of the compressor based on the pressure value of the compressor, thereby outputting a reset signal to the repetitive control portion according to the timing.

A control device for an electric compressor, capable of successfully controlling a drive motor of the compressor in response to the load fluctuation having complicated frequency components even when the motor is controlled in a sensorless manner, is provided. The control device for an electric compressor includes: a repetitive control portion 5 to which a rotation speed difference between a target rotation speed of a motor which drives the compressor and the estimated rotation speed is input to perform a repetitive operation using the rotation speed difference of one preceding cycle of the compressor, thereby reducing the rotation speed difference; a pressure detecting portion 1 for the compressor; and a reset signal generation portion 4 calculating a timing of one rotation of the compressor by counting the number of predetermined parts of load fluctuations of the compressor based on the pressure value of the compressor, thereby outputting a reset signal to the repetitive control portion according to the timing.

A measurement circuit includes first and second inputs for receiving first and second input signals which vary cyclically with the rotational position of a rotor of an electric motor; a phase detector circuit; and an observer circuit that estimates the frequency and phase of the first and second input signals. The phase detector circuit determines a phase difference between first and second estimated signals with a phase difference dependent on the phase difference indicated by the estimates, the first and second estimated signals varying in quadrature with each other and the first and second input signals by adding a multiplicative combination of the first input signal with the first estimated signal to a multiplicative combination of the second input signal with the second estimated signal to result in a sum signal dependent upon the phase difference, The observer circuit varies the estimates dependent upon the sum signal.

A measurement circuit includes first and second inputs for receiving first and second input signals which vary cyclically with the rotational position of a rotor of an electric motor; a phase detector circuit; and an observer circuit that estimates the frequency and phase of the first and second input signals. The phase detector circuit determines a phase difference between first and second estimated signals with a phase difference dependent on the phase difference indicated by the estimates, the first and second estimated signals varying in quadrature with each other and the first and second input signals by adding a multiplicative combination of the first input signal with the first estimated signal to a multiplicative combination of the second input signal with the second estimated signal to result in a sum signal dependent upon the phase difference, The observer circuit varies the estimates dependent upon the sum signal.