CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 USC § 119 to Korean Application No. 10-2019-0096971, filed on Aug. 8, 2019, and Korean Application No. 10-2019-0096972, filed on Aug. 8, 2019. The disclosure of the foregoing applications are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to a device for driving a plurality of motors and an electric apparatus having the same, and more particularly, to a device for driving a plurality of motors serially connected with each other by using a single inverter, and an electric apparatus having the same.

Meanwhile, the present disclosure relates to a device for driving a plurality of motors serially connected with each other in various modes by using a single inverter, and an electric apparatus having the same.

Meanwhile, the present disclosure relates to a device for stably driving a plurality of motors, while preventing the reduction of the voltage utilization of an inverter by using a single inverter, and an electric apparatus having the same.

BACKGROUND

A motor driving device is a device for driving a motor having a rotor that rotates and a stator wound around with a coil.

In recent years, in electric apparatuses, the use of motor is increasing, and in particular, a plurality of motors are employed to perform respective operations.

In order to drive a plurality of motors, when an inverter that supplies AC power to each of the motors, and a processor or microcomputer that controls the inverter are used, due to an increase in the number of inverters or an increase in the number of processors or microcomputers, an efficient structural design of an electric apparatus is difficult, and the manufacturing cost increases.

Meanwhile, for driving a plurality of motors, “IEEE Transactions on Industrial Electronics, vol. 62, no. 10, pp. 6096-6107, 2015” discloses a method of driving a plurality of three-phase motors by using a common inverter.

However, according to this method, since the same current flows through a plurality of three-phase motors, the plurality of three-phase motors rotate at the same speed. Accordingly, it is impossible to drive the motors at different speeds.

Meanwhile, for driving a plurality of motors, Korean Patent Application No. 10-2018-0025167 discloses that a plurality of motors are driven by using a single inverter, while a relay for switching is provided between the inverter and any a single motor.

According to this method, when the relay is turned on, a plurality of motors are driven in the same direction at the same speed by the same current, and when the relay is turned off, the plurality of motors are rotated in different directions at the same speed. Accordingly, it is impossible to drive motors at different speeds, when a plurality of motors are operated.

Meanwhile, Korean Patent Publication No. 10-2017-0087271 discloses that, for driving a plurality of motors, a plurality of motors are connected in parallel by using a single inverter.

However, according to this method, since a plurality of motors are connected in parallel, and the current output from the inverter is distributed to each motor, the voltage utilization of the inverter decreases to almost half, and voltage imbalance may occur in between the plurality of capacitors disposed in a DC terminal. According to the imbalance, the driving efficiency of the motor may be reduced due to current harmonics, torque pulsation of the motor, speed pulsation of the motor, or noise increase, or the like. In addition, it is difficult to simultaneously drive a plurality of motors at different speeds.

SUMMARY

The present disclosure has been made in view of the above problems, and provides a device for driving a plurality of motors serially connected with each other by using a single inverter, and an electric apparatus having the same.

The present disclosure further provides a device for driving a plurality of motors serially connected with each other in various modes by using a single inverter, and an electric apparatus having the same.

The present disclosure further provides a motor driving device which can stably drive a plurality of motors while preventing a reduction in voltage utilization of inverter by using a single inverter, and an electric apparatus having the same.

A device for driving a plurality of motors and an electric apparatus having the same according to an embodiment of the present disclosure include an inverter connected to a DC terminal, a multi-phase motor connected to the inverter, a single-phase motor serially connected to the multi-phase motor, and a first capacitor and a second capacitor serially connected to both ends of the DC terminal, wherein the single-phase motor is connected to the multi-phase motor, and a node between the first capacitor and the second capacitor.

Meanwhile, a neutral point of the multi-phase motor is connected to one end of the single phase motor, and the other end of the single-phase motor is connected to the node between the first capacitor and the second capacitor.

Meanwhile, an input terminal of the single-phase motor is electrically connected to a node to which each phase of the multi-phase motor is commonly connected, and an output terminal no of the single-phase motor is connected to the node between the first capacitor and the second capacitor.

Meanwhile, a neutral point of the multi-phase motor is connected to one end of the single phase motor, and a DC terminal neutral point, which is the node between the first capacitor and the second capacitor, is connected to the other end of the single-phase motor.

Meanwhile, the motor neutral point of the multi-phase motor is a node where current becomes zero according to a phase difference in a multi-phase AC system.

Meanwhile, a device for driving a plurality of motors and an electric apparatus having the same according to an embodiment of the present disclosure may further include a first current detector configured to detect a first current input to the multi-phase motor; and a second current detector configured to detect a second current input to the single-phase motor.

Meanwhile, a device for driving a plurality of motors and an electric apparatus having the same according to an embodiment of the present disclosure may further include a first voltage detector configured to detect a DC voltage across both ends of the first capacitor, and a second voltage detector configured to detect a DC voltage across both ends of the second capacitor.

Meanwhile, the current output from the inverter corresponds to a single sine wave, when driving the single-phase motor and the multi-phase motor at the same speed, and corresponds to a sum of a plurality of sine waves, when driving the single-phase motor and the multi-phase motor at different speeds.

Meanwhile, a device for driving a plurality of motors and an electric apparatus having the same according to an embodiment of the present disclosure may further include a controller configured to control the inverter, and the controller controls to drive the single-phase motor and the multi-phase motor at a same speed, to drive the single-phase motor and the multi-phase motor at different speeds, to drive only the single-phase motor, or to drive only the multi-phase motor.

Meanwhile, the number of a frequency of a current input to the multi-phase motor, when driving the single-phase motor and the multi-phase motor at the same speed, is smaller than the number of a frequency of a current input to the multi-phase motor, when driving the single-phase motor and the multi-phase motor at different speeds.

Meanwhile, the frequency of the current input to the multi-phase motor is one, when driving the single-phase motor and the multi-phase motor at the same speed, and the frequency of the current input to the multi-phase motor is two or more, when driving the single-phase motor and the multi-phase motor at different speeds.

Meanwhile, the current output from the inverter corresponds to a single sine wave, when driving the single-phase motor and the multi-phase motor at the same speed, and corresponds to a sum of a plurality of sine waves, when driving the single-phase motor and the multi-phase motor at different speeds.

Meanwhile, when driving the single-phase motor and the multi-phase motor at different speeds, the multi-phase motor rotates at a first speed corresponding to the first frequency of the first current input to the multi-phase motor, and the single-phase motor rotate at a second speed corresponding to the second frequency of the second current input to the single-phase motor.

Meanwhile, when driving the single-phase motor and the multi-phase motor at the same speed, the multi-phase motor and the single-phase motor are driven by an effective current of a same frequency.

Meanwhile, when driving the single-phase motor and the multi-phase motor at the same speed, in case a maximum level of an effective current of the multi-phase motor and a maximum level of an effective current of the single-phase motor are the same, a torque of the multi-phase motor is greater than a torque of the single-phase motor.

Meanwhile, when driving the single-phase motor and the multi-phase motor at different speeds, the multi-phase motor and the single-phase motor may be driven by effective currents of a different frequency.

Meanwhile, a device for driving a plurality of motors and an electric apparatus having the same according to an embodiment of the present disclosure may further include a first voltage detector configured to detect a DC voltage across both ends of the first capacitor, a second voltage detector configured to detect a DC voltage across both ends of the second capacitor, a first current detector configured to detect a first current input to the multi-phase motor, and a second current detector configured to detect a second current input to the single-phase motor.

Meanwhile, a device for driving a plurality of motors and an electric apparatus having the same according to an embodiment of the present disclosure may further include a controller, and the controller controls the frequency of the current input to the multi-phase motor to be one, when driving the single-phase motor and the multi-phase motor at the same speed, and controls the frequency of the current input to the multi-phase motor to be two or more, when driving the single-phase motor and the multi-phase motor at different speeds.

Meanwhile, the controller may calculate the neutral point voltage of the multi-phase motor.

Meanwhile, the operation period of the single-phase motor may be shorter than that of the multi-phase motor.

Meanwhile, when driving the single-phase motor and the multi-phase motor at different speeds, different currents flow through the multi-phase motor and the single-phase motor, and when driving only the multi-phase motor, a current flows through the multi-phase motor, and no current flows through the single-phase motor.

Meanwhile, when driving the single-phase motor and the multi-phase motor at different speeds, a first current having a first frequency and a second frequency is input to the multi-phase motor, and a second current having the second frequency is input to the single-phase motor.

Meanwhile, when driving the single-phase motor and the multi-phase motor at the same speed, a third current having a third frequency is input to the multi-phase motor, and a fourth current having the third frequency is input to the single-phase motor.

Meanwhile, a device for driving a plurality of motors and an electric apparatus having the same according to another embodiment of the present disclosure may further include a controller, and the controller controls to flow different currents through the multi-phase motor and the single-phase motor, when driving the single-phase motor and the multi-phase motor at different speeds, and controls to flow current through the multi-phase motor, and to flow no current through the single-phase motor.

Meanwhile, when driving at least the single-phase motor among the single-phase motor and the multi-phase motor, an electric potential between a motor neutral point of the multi-phase motor and a DC terminal neutral point between the first capacitor and the second capacitor is different, when driving only the multi-phase motor, an electric potential between the motor neutral point and the DC terminal neutral point is the same.

Meanwhile, a device for driving a plurality of motors and an electric apparatus having the same according to another embodiment of the present disclosure may further include a controller, and the controller controls an electric potential between a motor neutral point of the multi-phase motor and a DC terminal neutral point between the first capacitor and the second capacitor to be different, when driving at least the single-phase motor among the single-phase motor and the multi-phase motor, and controls an electric potential between the motor neutral point and the DC terminal neutral point to be the same, when driving only the multi-phase motor.

Meanwhile, the controller of the device for driving a plurality of motors according to another embodiment of the present disclosure may calculate the electric potential of the DC terminal neutral point, based on the first DC voltage detected by the first voltage detector and the second DC voltage detected by the second voltage detector, and may calculate the electric potential of the motor neutral point, based on the first current detected by the first current detector or the second current detected by the second current detector.

Meanwhile, when driving only the single-phase motor, all of upper switching elements of the inverter are turned on, or all of lower switching elements of the inverter are turned on.

Meanwhile, when driving only the single-phase motor, the phases of the current flowing in each phase of the multi-phase motor are the same.

Meanwhile, when driving only the single-phase motor, the sum of the currents flowing in each phase of the multi-phase motor flows in the single-phase motor.

Meanwhile, when all of upper switching elements of the inverter are turned on, or all of lower switching elements of the inverter are turned on, the level of current flowing in the single-phase motor is greater than the level of current flowing in each phase of the multi-phase motor.

Meanwhile, when driving only the single-phase motor, the first input current is input to the multi-phase motor, the effective current flowing through the multi-phase motor is zero, the second input current is input to the single-phase motor, and the effective current flowing through the multi-phase motor is second input current.

Meanwhile, when driving at least the multi-phase motor among the single-phase motor and the multi-phase motor, some of the upper-switching elements of the inverter are turned on, others are turned off, or some of the lower-switching elements of the inverter are turned on, and others are turned off.

Meanwhile, the multi-phase motor may include a fan motor, and the single-phase motor may include a pump motor.

