阅读说明：本技术 电动机驱动装置以及空调机 (Motor drive device and air conditioner ) 是由 宫森骏 浦慎一郎 志津圭一朗 于 2018-03-08 设计创作，主要内容包括：电动机驱动装置(1)具备：接线状态切换部(14),将电动机(3)的定子绕组(3u、3v、3w)的接线状态切换为三角形接线状态与星形接线状态中的任一个状态；逆变器(13),驱动电动机(3)；以及继电器电压检测电路(21),检测作为接线状态切换部(14)的电源电压的继电器电压(VR),并在继电器电压(VR)比阈值降低时将逆变器(13)停止。(A motor drive device (1) is provided with: a connection state switching unit (14) that switches the connection state of the stator windings (3u, 3v, 3w) of the motor (3) to either a delta connection state or a star connection state; an inverter (13) that drives the motor (3); and a relay voltage detection circuit (21) that detects a relay Voltage (VR) that is a power supply voltage of the connection state switching unit (14), and stops the inverter (13) when the relay Voltage (VR) falls below a threshold value.)

1. A motor drive device is characterized by comprising:

a switching unit that switches a connection state of a stator winding of the motor to any one of a 1 st connection state and a 2 nd connection state;

an inverter unit that drives the motor; and

and a power supply voltage detection unit that detects a 1 st power supply voltage that is a power supply voltage of the switching unit, and stops the inverter unit when the 1 st power supply voltage is lower than a threshold value.

2. The motor drive device according to claim 1,

when the 1 st power supply voltage is smaller than the 1 st value, the switching unit switches to the 2 nd connection state side,

when the 1 st power supply voltage is larger than the 1 st value, the switching unit switches to the 1 st connection state side,

the threshold is a value greater than the 1 st value.

3. The motor drive device according to claim 1 or 2,

the 1 st wiring state is a triangular wiring state,

the 2 nd wiring state is a star-connected state.

4. The motor drive device according to any one of claims 1 to 3,

the motor drive device is further provided with an overcurrent cutoff unit,

the current cutoff unit stops the inverter unit when a current flowing through the inverter unit exceeds a 1 st cutoff value when the stator winding is in the 1 st connection state,

when the stator winding is in the 2 nd connection state, the overcurrent cutoff unit stops the inverter unit when the current flowing through the inverter unit exceeds a 2 nd cutoff value smaller than a 1 st cutoff value.

5. The motor driving device according to any one of claims 1 to 4, further comprising:

a 1 st voltage conversion unit that converts an ac voltage supplied from an ac power supply into a dc voltage to generate a power supply voltage of the inverter unit; and

and a 2 nd voltage conversion unit that performs voltage conversion on the power supply voltage of the inverter unit to generate the 1 st power supply voltage.

6. The motor drive device according to any one of claims 1 to 5,

the inverter unit includes:

an inverter that generates electric power to be supplied to the motor; and

and a stop circuit for stopping the inverter upon receiving a stop signal from the outside.

7. An air conditioner is characterized by comprising:

the motor drive device according to any one of claims 1 to 6; and

and a motor driven by the motor driving device.

Technical Field

The present invention relates to a motor driving device and an air conditioner for driving a motor configured to be capable of switching a connection state of a stator winding.

Background

Under a rated condition that the rotation speed per unit time of the motor is high, the back electromotive force of the motor is small in a delta-connected state as a connected state of the stator winding as compared with a star-connected state, and therefore the motor can be operated to a higher rotation speed. On the other hand, in the star connection state, the back electromotive force of the motor is large as compared with the delta connection state, and therefore, the rotation speed cannot be increased to the delta connection state.

In the intermediate condition where the rotation speed per unit time of the motor is lower than the rated condition, the triangular wiring state has a larger current flowing through the motor than the star wiring state, and therefore, the power loss is larger. On the other hand, in the star connection state, the current flowing in the motor is small as compared with the delta connection state, so that the power loss is small.

A conventional motor drive device that drives a motor configured to be capable of switching a connection state of stator windings between a star connection state and a delta connection state includes an inverter and a relay for switching the connection state (see, for example, patent document 1). The conventional motor driving device operates the motor in a delta-connected state when the motor has a high load at a high rotation speed, and operates the motor in a star-connected state when the motor has a low load at a low rotation speed. Thus, the motor is operated at a high rotation speed under a high load, and an efficient operation with less power loss of the motor is performed under a low load.

Patent document 1: japanese laid-open patent publication No. 2009-216324

As described above, the motor is operated in the delta connection state at the time of high load, and the motor is operated in the star connection state at the time of low load. In this case, since the magnet of the motor may be demagnetized in the star connection state and the delta connection state and the value of the current flowing through the motor is different, it is necessary to perform control for cutting off the overcurrent using different values of the current in the star connection state and the delta connection state.

In general, since the magnet of the motor in the star connection state may be demagnetized and the value of the current flowing through the motor is lower than the value of the current flowing through the motor in the delta connection state, it is necessary to make the value of the current used for the control for cutting off the overcurrent in the star connection state (hereinafter referred to as "overcurrent cut-off value in the star connection state") smaller than the value of the current used for the control for cutting off the overcurrent in the delta connection state (hereinafter referred to as "overcurrent cut-off value in the delta connection state").

In a configuration in which a power supply for an inverter and a power supply for a relay for switching a connection state are generated from a common ac power supply, the connection state of a stator winding is changed to a delta connection state when the relay is turned on, and the connection state is changed to a star connection state when the relay is turned off, when the power supply voltage for the inverter is reduced due to an unexpected voltage reduction of the ac power supply in the delta connection state, the power supply voltage for the relay is also reduced, and there is a case where the relay cannot be maintained to be turned on, that is, the delta connection state cannot be maintained any more. In this case, even when the relay is turned off and switched to the star connection state, the inverter supplies the same current as the current supplied in the delta connection state to the motor. Then, control for cutting off the overcurrent in the delta connection state, that is, control for cutting off the overcurrent using the overcurrent cut-off value in the delta connection state, which is larger than the overcurrent cut-off value in the star connection state, is performed. Therefore, the value of the current supplied to the motor may exceed the overcurrent cutoff value in the star connection state, and there is a problem that the magnet of the motor may be demagnetized.

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to obtain a motor drive device capable of preventing demagnetization of a magnet of a motor even when a power supply voltage is reduced due to an unexpected voltage reduction or the like.

In order to solve the above problems and achieve the object, a motor drive device according to the present invention includes: a switching unit that switches a connection state of a stator winding of the motor to any one of a 1 st connection state and a 2 nd connection state; an inverter unit that drives the motor; and a power supply voltage detection unit that detects a 1 st power supply voltage that is a power supply voltage of the switching unit, and stops the inverter unit when the 1 st power supply voltage is lower than a threshold value.

The motor drive device according to the present invention has an effect of preventing demagnetization of the magnet of the motor even when the power supply voltage is reduced due to an unexpected voltage reduction or the like.

Drawings

Fig. 1 is a diagram showing an example of the configuration of a motor drive device according to embodiment 1 of the present invention.

Fig. 2 is a diagram showing a configuration example of the relay voltage detection circuit shown in fig. 1.

Fig. 3 is a diagram for explaining a triangular wiring state of the motor drive device according to embodiment 1 of the present invention.

Fig. 4 is a diagram for explaining a flow of demagnetizing the magnet of the motor shown in fig. 1.

Fig. 5 is a flowchart of a process of detecting a decrease in the relay voltage and stopping the inverter, which is executed by the motor drive apparatus shown in fig. 1.

Fig. 6 is a diagram for explaining a flow of preventing the magnets of the motor shown in fig. 1 from demagnetizing.

Fig. 7 is a diagram for explaining a time lag between the smoothing capacitor voltage and the relay voltage in the motor drive device shown in fig. 1.

Fig. 8 is a functional block diagram showing a configuration of an air conditioner according to embodiment 2 of the present invention.

Detailed Description

Hereinafter, a motor drive device and an air conditioner according to an embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiment.