Electric machine system

An electric machine system comprising:

• an electric machine comprising:
• a rotor that comprises a magnet and rotates together with a shaft;
• and
• a coil fixedly disposed to surround the rotor;
• a power converter configured to output an output current to the coil of the electric machine;
• and
• at least one processor configured to:
• receive an abnormality signal indicating an abnormal situation, and
• output a demagnetization control signal to the power converter in response to receiving the abnormality signal,
• wherein the power converter is configured to output a demagnetization current to the coil, in response to receiving the demagnetization control signal from the processor, and the demagnetization current flows through the coil and demagnetizes the magnet of the rotor, so as to reduce a magnitude of a fault current,
• wherein the demagnetization current causes an external magnetic flux to be applied to the magnet, and
• wherein the power converter is configured to perform a control such that a demagnetization current flowing through a coil at a position where a d-axis component is larger than a q-axis component becomes larger than a demagnetization current flowing through a coil at a position where the q-axis component is larger than the d-axis component, in response to the input of the demagnetization control signal from the processor.

An electric machine system comprising:

• a power converter;
• and
• at least one processor configured to:
• receive an abnormality signal indicating an abnormal situation, and
• output a demagnetization control signal to the power converter in response to receiving the abnormality signal,
• wherein the power converter is configured to output a demagnetization current for to a coil of an electric machine, in response to receiving the demagnetization control signal from the processor, and the demagnetization current flows through the coil and demagnetizes the magnet of the rotor, so as to reduce a magnitude of a fault current,
• wherein the demagnetization current causes an external magnetic flux to be applied to the magnet, and
• wherein a surface permanent magnet forms the magnet having a d-axis along a line connecting an N-pole and an S-pole of the surface permanent magnet and a q-axis which is orthogonal to the d-axis.