Electric working machine and motor controller

An electric working machine, comprising:

• a brushless motor;
• and
• a motor controller configured to control the brushless motor,
• wherein
• the brushless motor includes:
• a rotor including a plurality of magnetic poles;
• a stator including a plurality of teeth facing the rotor;
• and
• coils wound around the teeth, the coils being configured to generate magnetic forces in the teeth according to voltages applied on a first phase terminal, a second phase terminal, and a third phase terminal,
• the motor controller includes:
• a first upper switching element connecting the first phase terminal and a positive-side potential of a power supply;
• a first lower switching element connecting the first phase terminal and a negative-side potential of the power supply;
• a second upper switching element connecting the second phase terminal and the positive-side potential of the power supply;
• a second lower switching element connecting the second phase terminal and the negative-side potential of the power supply;
• a third upper switching element connecting the third phase terminal and the positive-side potential of the power supply;
• a third lower switching element connecting the third phase terminal and the negative-side potential of the power supply;
• and
• a control unit configured to switch each of the first upper switching element, the first lower switching element, the second upper switching element, the second lower switching element, the third upper switching element, and the third lower switching element between a conductive state and a non-conductive state,
• the control unit is configured to execute a short-circuit braking operation for applying a braking force to the brushless motor by bringing the first upper switching element, the second upper switching element, and the third upper switching element into the non-conductive state and bringing the first lower switching element, the second lower switching element, and the third lower switching element into the conductive state,
• before executing the short-circuit braking operation, the control unit is configured to execute a de-energization operation for bringing the first upper switching element, the first lower switching element, the second upper switching element, the second lower switching element, the third upper switching element, and the third lower switching element into the non-conductive state, and
• the control unit is configured to start the short-circuit braking operation at a timing when induced voltages of two of the first phase terminal, the second phase terminal, and the third phase terminal become substantially equal to each other after the de-energization operation.

A motor controller configured to control a brushless motor, wherein

• the brushless motor includes:
• a rotor including a plurality of magnetic poles;
• a stator including a plurality of teeth facing the rotor;
• and
• coils wound around the teeth, the coils being configured to generate magnetic forces in the teeth according to voltages applied on a first phase terminal, a second phase terminal, and a third phase terminal,
• the motor controller comprises:
• a first upper switching element connecting the first phase terminal and a positive-side potential of a power supply;
• a first lower switching element connecting the first phase terminal and a negative-side potential of a power supply;
• a second upper switching element connecting the second phase terminal and the positive-side potential of the power supply;
• a second lower switching element connecting the second phase terminal and the negative-side potential of the power supply;
• a third upper switching element connecting the third phase terminal and the positive-side potential of the power supply;
• a third lower switching element connecting the third phase terminal and the negative-side potential of the power supply;
• and
• a control unit configured to switch each of the first upper switching element, the first lower switching element, the second upper switching element, the second lower switching element, the third upper switching element, and the third lower switching element between a conductive state and a non-conductive state,
• the control unit is configured to execute a short-circuit braking operation for applying a braking force to the brushless motor by bringing the first upper switching element, the second upper switching element, and the third upper switching element into the non-conductive state and bringing the first lower switching element, the second lower switching element, and the third lower switching element into the conductive state,
• the control unit is configured to start the short-circuit braking operation at a predetermined timing, and
• when the short-circuit braking operation is started at the predetermined timing, polarities of induced voltages of the first phase terminal, the second phase terminal, and the third phase terminal are reversed by a time when an electrical angle of the brushless motor increases by 180 degrees from the start of the short-circuit braking operation.