We Claim:
1. A driving device used with a compressor including a motor
including coils and to drive the motor, the compressor including
a compression mechanism, a shell, and a discharge pipe, the
compression mechanism being driven by the motor, the shell
covering the motor and the compression mechanism, the driving
device comprising:
an inverter connected to the coils;
a connection switching unit to switch a connection state of the coils between a first connection state and a second connection state;
a controller to control the inverter and the connection switching unit; and
a compressor state detection unit to detect a state of the compressor, wherein
when the connection state of the coils is the first connection state, the controller controls the motor based on a first detection value detected by the compressor state detection unit and a first threshold, and
when the connection state of the coils is the second connection state, the controller controls the motor based on a second detection value detected by the compressor state detection unit and a second threshold.
2. The driving device according to claim 1, wherein the state of the compressor is a temperature of at least one of the shell, the discharge pipe, a refrigerant in the compressor, and the motor disposed in the compressor.
3. The driving device according to claim 2, wherein when the first detection value is larger than the first threshold, the controller controls the motor so that the at least one temperature detected by the compressor state detection unit

decreases.
4. The driving device according to claim 2 or 3, wherein when the second detection value is larger than the second threshold, the controller controls the motor so that the at least one temperature detected by the compressor state detection unit decreases.
5. The driving device according to any one of claims 1 to 4, wherein the controller changes rotation speed of the motor to control the motor.
6. The driving device according to any one of claims 1 to 5, wherein a line voltage of the inverter in the second connection state is lower than a line voltage of the inverter in the first connection state.
7. The driving device according to any one of claims 1 to 6, wherein the second threshold is larger than the first threshold.
8. The driving device according to any one of claims 1 to 7, wherein the coils are three-phase coils.
9. The driving device according to claim 8, wherein the first connection state is a state in which the three-phase coils are connected in Y connection.
10. The driving device according to claim 8 or 9, wherein the second connection state is a state in which the three-phase coils are connected in delta connection.
11. The driving device according to any one of claims 1 to 7, wherein
the coils are three-phase coils connected in Y connection

or delta connection,
the first connection state is a state in which the three-phase coils are connected in series in each phase, and
the second connection state is a state in which the three-phase coils are connected in parallel in each phase.
12. The driving device according to any one of claims 1 to 11, wherein the compressor state detection unit is a temperature sensor.
13. The driving device according to any one of claims 1 to 12, wherein the compressor state detection unit is fixed to the discharge pipe.
14. The driving device according to any one of claims 1 to 13, wherein
the motor includes a permanent magnet forming a magnetic pole,
the permanent magnet is a rare earth magnet containing neodymium, iron, and boron as main components, and
the permanent magnet has residual magnetic flux density of 1.36 T to 1.42 T, a coercive force of 1671 kA/m to 1989 kA/m, and a maximum energy product of 354 kJ/m3 to 398 kJ/m3.
15. An air conditioner comprising:
a compressor including a motor including coils, a compression mechanism driven by the motor, a shell covering the motor and the compression mechanism, and a discharge pipe;
an inverter connected to the coils;
a connection switching unit to switch a connection state of the coils between a first connection state and a second connection state;
a controller to control the inverter and the connection switching unit; and

a compressor state detection unit to detect a state of the compressor, wherein
when the connection state of the coils is the first connection state, the controller controls the motor based on a first detection value detected by the compressor state detection unit and a first threshold, and
when the connection state of the coils is the second connection state, the controller controls the motor based on a second detection value detected by the compressor state detection unit and a second threshold.
16. A method for controlling a compressor including a motor in which a connection state of coils can be switched between a first connection state and a second connection state, the method comprising:
detecting a state of the compressor as a first detection value when the connection state of the coils is the first connection state;
controlling the motor based on the first detection value and a first threshold when the connection state of the coils is the first connection state;
detecting the state of the compressor as a second detection value when the connection state of the coils is the second connection state; and
controlling the motor based on the second detection value and a second threshold when the connection state of the coils is the second connection state.