Rectifier device and motor drive device

Abstract

The present disclosure provides a rectifying device and a motor drive device that are highly resistant to frequent start and stop. A rectifying device according to an embodiment of the present disclosure includes a bridge circuit that extracts positive and negative voltage components from an alternating-current power supply voltage, a smoothing capacitor that smoothes an output voltage of the bridge circuit, a pre-charge resistor provided between the bridge circuit and the smoothing capacitor for suppressing an inrush current, a charge switch provided in parallel with the pre-charge resistor, and a control unit that controls an on-off state of the charge switch, wherein the control unit closes the charge switch when it is determined that a voltage applied across the pre-charge resistor is below a prescribed resistor voltage threshold when start of application of the alternating-current power supply voltage to the bridge circuit is to be initiated.

Description

TECHNICAL FIELD

[0001] The present application relates to a rectifying device and a motor drive device. BACKGROUND

[0002] A rectifying device that rectifies alternating current by a diode bridge and reduces voltage variation by a smoothing capacitor is widely used. For example, a motor drive device that converts alternating current into direct current by a rectifying device and converts the direct current outputted from the rectifying device into alternating current of an arbitrary frequency by an inverter to drive a motor is being put into practical use.

[0003] Such a rectifying device, immediately after starting, since the smoothing capacitor is not charged, the voltage between both ends of the smoothing capacitor is small, and thus the difference from the output voltage of the diode bridge is large, and a large impact current can flow. As a technique for suppressing such an impact current, for example, in Patent Literature 1, a motor drive device is proposed that has an initial charging section that has a switch section for opening and closing a circuit between an alternating current-direct current conversion section (diode bridge) and an electric power storage section (smoothing capacitor), and a charging resistor connected in parallel to the switch section, and before starting to drive a motor, the switch section of the initial charging section is opened, and the electric power storage section is initially charged by a direct current from the alternating current-direct current conversion section that flows through the charging resistor.

[0004] In the motor drive device of Patent Literature 1, during initial charging from immediately after starting the motor drive device until starting to drive the motor, by opening the switch section (OFF), a direct current outputted from the alternating current-direct current conversion section flows into the electric power storage section through the charging resistor, and the electric power storage section is charged. Then, when the electric power storage section is charged to a prescribed voltage, the switch section is closed (ON) to short-circuit both ends of the charging resistor, and the initial charging operation is completed.

[0005] Prior art documents

[0006] Patent documents

[0007] Patent Literature 1: Japanese Patent Application Laid-Open No. 2017-135955 SUMMARY

[0008] Problems to be solved by the invention

[0009] In adjusting and maintaining a device that has a motor driven by a motor drive device having a rectifying device and an inverter, for safety, for example, work is often performed in a state where the power supply of the motor drive device is cut off by operating an emergency stop button or opening a main power supply switch. In the case where fine adjustment and trial operation of the device are repeatedly performed, the rectifying device is frequently started and stopped.

[0010] In the motor drive device of Patent Literature 1, the contact of the switch section connected in parallel with the charge resistance jumps at the time of closing, and the contact is deteriorated due to arc discharge. Therefore, when the motor drive device of Patent Literature 1 frequently performs start and stop, the contact of the switch section can be deteriorated due to abrasion. Therefore, a rectifier device and a motor drive device having high resistance to frequent start and stop are desired.

[0011] Solution to the problem

[0012] The rectifier device according to one embodiment of the present disclosure includes a bridge circuit that extracts positive and negative voltage components from an alternating-current power supply voltage, a smoothing capacitor that smoothes an output voltage of the bridge circuit, a preliminary charge resistance that is provided between the bridge circuit and the smoothing capacitor and that is used to suppress an inrush current, a charge switch that is provided in parallel with the preliminary charge resistance, and a control section that controls an on-off state of the charge switch, wherein the control section closes the charge switch when it is determined that a voltage applied across the preliminary charge resistance is equal to or lower than a prescribed resistance voltage threshold value at a time when the bridge circuit is to start being applied with the alternating-current power supply voltage.

[0013] Effects of the invention

[0014] The rectifier device according to one embodiment of the present disclosure has high resistance to frequent start and stop. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 FIG. 1 is a circuit diagram showing a configuration of a motor drive device according to a first embodiment of the present disclosure.

[0016] Figure 2 FIG. 2 is a circuit diagram showing a configuration of a motor drive device according to a second embodiment of the present disclosure.

[0017] Figure 3 FIG. 3 is a circuit diagram showing a configuration of a motor drive device according to a third embodiment of the present disclosure.

[0018] Explanation of reference numerals

[0019] 1, 1A, 1B: rectifier device; 2: inverter; 10: bridge circuit; 20: smoothing capacitor; 30: preliminary charge resistance; 40, 40B: charge switch; 50: output voltage detection circuit; 60: power supply switch; 70, 70A, 70B: control section; 80: power supply voltage detection circuit; 90: step-down circuit; 100, 100A, 100B: motor drive device; M: motor; S: alternating-current power supply. DETAILED DESCRIPTION

[0020] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Figure 1 is a schematic view showing a structure of a motor drive device 100 of a first embodiment of the present disclosure.

[0021] The motor drive device 100 is provided with a rectifier device 1 that converts an alternating-current power supply voltage supplied from an alternating-current power supply S into a direct-current voltage, and an inverter 2 that converts the direct-current output from the rectifier device 1 into an alternating current of an arbitrary frequency and applies it to a motor M. The rectifier device 1 is one embodiment of the rectifier device according to the present disclosure.

[0022] The rectifier device 1 is provided with a bridge circuit 10 that extracts positive and negative voltage components from the alternating-current power supply voltage, a smoothing capacitor 20 that smoothes the output voltage of the bridge circuit 10, a pre-charge resistor 30 that is provided between the bridge circuit 10 and the smoothing capacitor 20 and is used to suppress an inrush current, a charge switch 40 that is provided in parallel with the pre-charge resistor 30, an output voltage detection circuit 50 that detects the voltage between both ends of the smoothing capacitor 20, a power supply switch 60 that is used to apply the alternating-current power supply voltage supplied from the alternating-current power supply S to the bridge circuit 10, and a control section 70 that controls the on-off state of the charge switch 40.

[0023] The bridge circuit 10 can be configured as a known three-phase diode bridge circuit, that is, with diodes 11, 12, 13 that extract positive voltages of each phase of the alternating-current power supply voltage, and diodes 14, 15, 16 that extract negative voltages of each phase of the alternating-current power supply voltage. The bridge circuit 10 applies the positive voltages extracted by the diodes 11, 12, 13 to one end of the smoothing capacitor 20 via the pre-charge resistor 30 and the charge switch 40, and applies the negative voltages extracted by the diodes 14, 15, 16 directly to the other end of the smoothing capacitor 20.

[0024] The smoothing capacitor 20 is charged by a current supplied from the bridge circuit 10 by using a voltage difference between the bridge circuit 10. This smoothing capacitor 20 outputs a voltage in which a ripple of the output voltage of the bridge circuit 10 caused by the waveform of the alternating-current power supply voltage is smoothed, to the inverter 2.

[0025] The pre-charge resistor 30 suppresses a large inrush current that flows from the bridge circuit 10 to the smoothing capacitor 20 due to a large voltage difference between the output voltage of the bridge circuit 10 and the smoothing capacitor 20 at the time of start when the smoothing capacitor 20 is not charged.

[0026] As will be described later, the on-off state of the charging switch 40 is controlled by the control section 70, and in the case where the voltage difference between the bridge circuit 10 and the smoothing capacitor 20 is small, the charging switch 40 is closed to form a circuit in which the preparatory charging resistor 30 is provided as a branch so that a greater current can be supplied from the bridge circuit 10 to the smoothing capacitor 20.

[0027] The output voltage detection circuit 50 detects the voltage between the terminals of the smoothing capacitor 20, that is, the voltage output to the inverter 2. The output voltage detection circuit 50 inputs a detection signal indicating the detected voltage value to the control section 70.

[0028] The power supply switch 60 is provided in the circuit between the AC power supply S and the bridge circuit 10, and is controlled by the control section 70 to open and close the circuit. The power supply switch 60 is preferably provided as a normally open type switch which is in an open state when no signal is input from the control section 70.

[0029] The control section 70 closes the charging switch 40 when it is determined that the voltage applied between the terminals of the preparatory charging resistor 30 is below a prescribed resistance voltage threshold value when it is to start applying the AC power supply voltage to the bridge circuit 10. The control section 70 can be realized by causing a computer device provided with a memory, a CPU, an input / output signal interface, and the like to execute an appropriate program. The power required for the control section 70 to operate is supplied directly from the upstream side of the power supply switch 60 or via a control power supply device.

[0030] The control section 70 in the present embodiment determines that the voltage applied between the terminals of the preparatory charging resistor 30 is below the resistance voltage threshold value when the detection value of the output voltage detection circuit 50 is below a prescribed output threshold value. Normally, it can be considered that the voltage of the AC power supply S is constant. In this case, it can be considered that the output voltage of the bridge circuit 10 is also constant, and therefore the detection value of the output voltage detection circuit 50 and the voltage applied between the terminals of the preparatory charging resistor 30 are in a correlation relationship. Thus, by setting the output threshold value below which to a value corresponding to the resistance voltage threshold value, it is possible to determine whether the voltage applied between the terminals of the preparatory charging resistor 30 is below the resistance voltage threshold value.

[0031] The control section 70 closes the power switch 60 after confirming the voltage across the two terminals of the pre-charge resistor 30 to determine the state of the charge switch 40. That is, the control section 70, in the case where it is determined that the voltage applied across the two terminals of the pre-charge resistor 30 is below the resistor voltage threshold, causes the charge switch 40 to be in the closed state, and then closes the power switch 60 to start supplying power from the bridge circuit 10 to the smoothing capacitor 20; the control section 70, in the case where it is determined that the voltage applied across the two terminals of the pre-charge resistor 30 exceeds the resistor voltage threshold, causes the charge switch 40 to be in the open state, and then closes the power switch 60 to start supplying power from the bridge circuit 10 to the smoothing capacitor 20.

[0032] Thus, for example, in the case where power is supplied immediately after the power supply of the motor drive device 100 is turned off, when the control section 70 is started in a state where the smoothing capacitor 20 is charged, since the control section 70 closes the charge switch 40 before closing the power switch 60, current can flow through the charge switch 40 after the bounce of the contacts of the charge switch 40 subsides. Thus, the wear of the contacts caused by arc discharge at the time of bounce when the charge switch 40 is closed can be suppressed.

[0033] The control section 70 maintains the state where the charge switch 40 is closed until it is determined that the voltage applied across the two terminals of the pre-charge resistor 30 becomes the resistor voltage threshold or another prescribed threshold. Thus, unnecessary power loss due to heat loss in the pre-charge resistor 30 can be prevented, and the number of times the charge switch 40 is opened and closed can be reduced to suppress the wear of the contacts caused by arc discharge that occurs in conjunction with bounce when the charge switch 40 is closed.

[0034] The inverter 2 converts the direct-current voltage across the two terminals of the smoothing capacitor 20 into a three-phase alternating-current voltage of an arbitrary frequency. Specifically, the inverter 2 can be configured as a known structure having a plurality of switching elements that extract the positive and negative voltages of the smoothing capacitor 20 at different timings for each phase.

[0035] As described above, since the rectification device 1 closes the power switch 60 after confirming the voltage applied across the two terminals of the pre-charge resistor 30 at the time of start-up to set the charge switch 40 to an appropriate state, the wear of the contacts caused by arc discharge that occurs in conjunction with bounce when the charge switch 40 is closed can be suppressed. Thus, the rectification device 1 and the motor drive device 100 provided with the rectification device 1 have high resistance to frequent start-up and stop.

[0036] Next, the structure of the motor drive device 100A of the second embodiment of the present disclosure is shown in FIG. 2. For the motor drive device 100A of the present embodiment, the same components as those of the motor drive device 100 of the first embodiment are denoted by the same reference numerals, and a description thereof will be omitted. Figure 2 Figure 1 ​The same components as those of the motor drive device 100 are given the same reference numerals to omit repeated description.

[0037] The motor drive device 100A includes a rectifier 1A that converts an alternating-current power supply voltage supplied from an alternating-current power supply S into a direct-current voltage, and an inverter 2 that converts the direct-current output from the rectifier 1A into an alternating current of an arbitrary frequency and applies the alternating current to a motor M. The rectifier 1A is one embodiment of the rectifier according to the present disclosure.

[0038] The rectifier 1A includes a bridge circuit 10 that extracts positive and negative voltage components from the alternating-current power supply voltage, a smoothing capacitor 20 that smoothes the output voltage of the bridge circuit 10, a pre-charge resistor 30 that is provided between the bridge circuit 10 and the smoothing capacitor 20 and is used to suppress an inrush current, a charge switch 40 that is provided in parallel with the pre-charge resistor 30, an output voltage detection circuit 50 that detects the voltage between both ends of the smoothing capacitor 20, a power supply switch 60 that is used to apply the alternating-current power supply voltage supplied from the alternating-current power supply S to the bridge circuit 10, a power supply voltage detection circuit 80 that detects the voltage of the alternating-current power supply voltage, and a control section 70A that controls the on-off state of the charge switch 40.

[0039] The power supply voltage detection circuit 80 is provided between the alternating-current power supply S and the power supply switch 60. The power supply voltage detection circuit 80 can be configured to have a plurality of phase voltage detectors 81 that detect the voltage of each phase of the alternating-current power supply voltage. The detection value of the power supply voltage detection circuit 80 can be either a root mean square value or a peak value.

[0040] When it is to be started to apply the alternating-current power supply voltage to the bridge circuit 10, the control section 70A closes the charge switch 40 in a case where it is determined that the voltage applied between both ends of the pre-charge resistor 30 is equal to or lower than a prescribed resistor voltage threshold value. The control section 70A can be realized by causing a computer device provided with a memory, a CPU, an input-output signal interface, and the like to execute an appropriate program. The power required for the control section 70A to operate is supplied directly from the upstream side of the power supply switch 60 or via a control power supply device.

[0041] The control section 70A in the present embodiment determines that the voltage applied between both ends of the pre-charge resistor 30 is equal to or lower than the resistor voltage threshold value in a case where the difference between the detection value of the output voltage detection circuit 50 and the detection value of the power supply voltage detection circuit 80 is equal to or lower than a prescribed difference threshold value.

[0042] In the present embodiment, the voltage applied to the pre-charge resistor 30 can be accurately confirmed even in a case where the alternating-current power supply voltage supplied from the alternating-current power supply S fluctuates, and thus it is possible to appropriately switch between the suppression of the inrush current and the suppression of the wear of the contacts of the charge switch 40 using the pre-charge resistor 30.

[0043] Also, in Figure 3 The structure of a motor drive device 100B of a third embodiment of the present disclosure is shown in Figure 1 The same reference numerals are given to the same constituent elements as those of the motor drive device 100, and repeated explanation is omitted.

[0044] The motor drive device 100B includes a rectifier device IB that converts an alternating-current power supply voltage supplied from an alternating-current power supply S into a direct-current voltage, and an inverter 2 that converts the direct-current output from the rectifier device IB into an alternating current of an arbitrary frequency and applies it to a motor M. The rectifier device IB is one embodiment of the rectifier device according to the present disclosure.

[0045] The rectifier device IB includes a bridge circuit 10 that extracts positive and negative voltage components from the alternating-current power supply voltage, a smoothing capacitor 20 that smoothes the output voltage of the bridge circuit 10, a pre-charge resistor 30 that is provided between the bridge circuit 10 and the smoothing capacitor 20 and is used to suppress an inrush current, a charge switch 40B that is provided in parallel with the pre-charge resistor 30, an output voltage detection circuit 50 that detects the voltage between both ends of the smoothing capacitor 20, a control section 70B that controls the on-off state of the charge switch 40B, and a step-down circuit 90 that steps down the output voltage of the smoothing capacitor 20 to a prescribed voltage and supplies it to the control section 70B. In the rectifier device IB of the present embodiment, the alternating-current power supply S is directly connected to the bridge circuit 10 without passing through a power supply switch.

[0046] The charge switch 40B is a normally open type relay that is closed only during a period in which a signal from the control section 70B is input.

[0047] The control section 70B closes the charge switch 40B when it is determined that the voltage applied between both ends of the pre-charge resistor 30 is below a prescribed resistance voltage threshold value, when it is time to start applying the alternating-current power supply voltage to the bridge circuit 10. The control section 70B can be implemented by causing a computer device that includes a memory, a CPU, an input-output signal interface, and the like to execute an appropriate program. The power required for the control section 70B to operate is supplied from the step-down circuit 90.

[0048] The control unit 70B in this embodiment determines that the voltage applied across the two ends of the pre-charge resistor 30 is below the resistor voltage threshold value in a case where the detected value of the output voltage detection circuit 50 is above the prescribed output threshold value or in a case where power from the step-down circuit 90 is being supplied. That is, the control unit 70B is configured to actively turn off the control signal so that the charging switch 40B is opened in a case where the detected value of the output voltage detection circuit 50 is below the prescribed output threshold value or in a case where the supply of power from the step-down circuit 90 is stopped, and the control unit 70B is unable to output the control signal that closes the charging switch 40, thereby opening the charging switch 40.

[0049] The step-down circuit 90 is a circuit that steps down the output voltage of the smoothing capacitor 20 to the operating voltage of the control unit 70B. The step-down circuit 90 is configured to output a voltage that enables the control unit 70B to continue the control operation at least during a period in which the voltage applied across the two ends of the pre-charge resistor 30 exceeds the resistor voltage threshold value after the supply of the alternating-current power supply voltage to the bridge circuit 10 is stopped and the supply is started again.

[0050] In this way, the control unit 70B that opens and closes the charging switch 40 in accordance with the voltage across the two ends of the smoothing capacitor 20 maintains the state in which the charging switch 40 is closed in a case where the supply of the alternating-current power supply voltage is resumed before the smoothing capacitor 20 is discharged by a fixed amount from when the supply of the alternating-current power supply voltage is cut off, and thus the wear of the contacts caused by the bounce of the charging switch 40 can be suppressed. In addition, the control unit 70B is restarted in the state in which the charging switch 40 is opened in a case where the supply of the alternating-current power supply voltage is resumed after the smoothing capacitor 20 is discharged by a fixed amount from when the supply of the alternating-current power supply voltage is cut off, and thus the inrush current can be effectively suppressed by charging the smoothing capacitor 20 via the pre-charge resistor 30.

[0051] The embodiments of the rectifying device and the motor drive device according to the present disclosure have been described above, but the rectifying device and the motor drive device according to the present disclosure are not limited to the above-described embodiments. In addition, the effects described with respect to the above-described embodiments of the rectifying device and the motor drive device are merely examples of the most preferable effects of the rectifying device and the motor drive device according to the present disclosure, and the effects of the rectifying device and the motor drive device according to the present disclosure are not limited to the effects described in the above-described embodiments.

[0052] The rectifying device according to the present disclosure can also be used to supply a direct-current voltage to an electrical circuit other than an inverter. In addition, the rectifying device according to the present disclosure can also be, for example, a bridge circuit provided with a switching element that allows current to flow in a reverse direction with respect to each diode, and provided with a function of converting a direct-current voltage supplied in a reverse direction from an output side of a smoothing capacitor into alternating current synchronized with an alternating-current power supply voltage and regenerating it in the alternating-current power supply. Thus, the inverter in the motor drive device according to the present disclosure can also be configured to use a motor as a generator, and can function as a rectifying device that converts alternating current supplied in a reverse direction from the motor into direct current.

Claims

1. A rectifying device, characterized by, Possessing: a bridge circuit that extracts positive and negative voltage components from an AC power supply voltage; a smoothing capacitor that smoothes an output voltage of the bridge circuit; a preliminary charge resistor provided between the bridge circuit and the smoothing capacitor for suppressing an inrush current; a charge switch provided in parallel with the preliminary charge resistor; a power supply switch for applying the AC power supply voltage to the bridge circuit; and a control section that controls on-off states of the charge switch and the power supply switch, wherein, when the application of the AC power supply voltage to the bridge circuit is to be started, the control section brings the charge switch to a closed state if it is determined that a voltage applied across the preliminary charge resistor is below a prescribed resistor voltage threshold, and thereafter closes the power supply switch, and the control section brings the charge switch to an open state if it is determined that the voltage applied across the preliminary charge resistor exceeds the resistor voltage threshold, and thereafter closes the power supply switch.

2. The rectifying device according to claim 1, characterized by further possessing an output voltage detection circuit that detects a voltage across the smoothing capacitor, the control section determining that the voltage applied across the preliminary charge resistor is below the resistor voltage threshold if a detection value of the output voltage detection circuit is below a prescribed output threshold. Further possessing: an output voltage detection circuit that detects a voltage across the smoothing capacitor; and 3. The rectifying device of claim 1, wherein a power supply voltage detection circuit that detects a voltage of the AC power supply voltage, the control section determining that the voltage applied across the preliminary charge resistor is below the resistor voltage threshold if a difference between a detection value of the output voltage detection circuit and a detection value of the power supply voltage detection circuit is below a prescribed difference threshold. Possessing: the rectifying device according to any one of claims 1 to 3; and an inverter that converts an output of the rectifying device into an AC. ​ 4. An electric motor drive apparatus characterized by comprising: ​

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