Magnetic gap length estimating device, magnetic gap length estimating method, and driving device for rotating electric machine

A magnetic gap length estimating method for estimating a magnetic gap length in an M-group N-phase rotating electric machine to be driven by an inverter where M represents a natural number and N represents a natural number not smaller than 2, the rotating electric machine being formed by connection wires with a phase difference in electrical angle among phases being 360/N degrees, the magnetic gap length estimating method comprising:

• a voltage acquiring step of acquiring a no-load-induced line-to-line voltage induced between the connection wires under no load;
• and
• a magnetic gap estimating step of estimating the magnetic gap length, wherein
• the magnetic gap estimating step includes
• a spectrum analysis step of converting the no-load-induced line-to-line voltage acquired in the voltage acquiring step into amplitudes and phases for respective frequencies,
• a frequency analysis step of extracting amplitudes and phases of a fundamental wave component and an Nth-order harmonic component of the no-load-induced line-to-line voltage from among the amplitudes and the phases, for the respective frequencies, that have been obtained through the conversion in the spectrum analysis step, and
• an estimating-and-calculating step of estimating the magnetic gap length from the amplitudes and the phases, of the fundamental wave component and the Nth-order harmonic component of the no-load-induced line-to-line voltage, that have been extracted in the frequency analysis step.

A driving device for an M-group N-phase rotating electric machine to be driven by an inverter where M represents a natural number and N represents a natural number not smaller than 2, the rotating electric machine being formed by connection wires with a phase difference in electrical angle among phases being 360/N degrees, the driving device comprising:

• a voltage acquiring circuitry which acquires a no-load-induced line-to-line voltage induced between the connection wires under no load;
• a magnetic gap estimating circuitry which estimates a magnetic gap length in the rotating electric machine, the magnetic gap estimating circuitry including
• a spectrum analysis circuitry which converts the no-load-induced line-to-line voltage acquired by the voltage acquiring circuitry into amplitudes and phases for respective frequencies,
• a frequency analysis circuitry which extracts amplitudes and phases of a fundamental wave component and an Nth-order harmonic component of the no-load-induced line-to-line voltage from among the amplitudes and the phases, for the respective frequencies, that have been obtained through the conversion by the spectrum analysis circuitry, and
• an estimating-and-calculating circuitry which estimates the magnetic gap length from the amplitudes and the phases, of the fundamental wave component and the Nth-order harmonic component of the no-load-induced line-to-line voltage, that have been extracted by the frequency analysis circuitry;
• and
• a control parameter calculating circuitry which calculates a control parameter for the inverter on the basis of the magnetic gap length estimated by the magnetic gap estimating circuitry.