KR20220081294A - Circuitry for preventing in-rush current of power supply circuit for driving motor, and method for preventing in-rush current - Google Patents

Abstract

In the inrush current limiting circuit which has a rectifier circuit and a smoothing capacitor and which limits the inrush current in a power supply circuit for driving a motor, it makes it possible to start a motor earlier after starting a power supply circuit.
The inrush current limiting circuit has a resistor 13 for limiting inrush current inserted between the input of the external AC power supply 10 and the power supply circuit 15, and a contact that can short-circuit both ends of the resistor 13 The short circuit relay 14, the AC voltage detector 11 which detects the voltage of the AC power in a position closer to the AC power supply 10 than the resistor 13, and the smoothing capacitor 16 in the power supply circuit 15 are charged Control for changing the contact point of the short circuit relay 14 from open to closed based on the DC voltage detector 19 for detecting a voltage, and the detection results from both the AC voltage detector 11 and the DC voltage detector 19 . It has a control unit 20 that performs

Description

CIRCUITRY FOR PREVENTING IN-RUSH CURRENT OF POWER SUPPLY CIRCUIT FOR DRIVING MOTOR, AND METHOD FOR PREVENTING IN-RUSH CURRENT

The present invention relates to a circuit and method for limiting an inrush current in a power supply circuit for driving a motor.

AC motors such as synchronous motors and induction motors are used as motors for driving each axis of the industrial robot, but servo drivers that drive and servo control these motors have an inverter function, and DC power is usually supplied. . The DC power is obtained by rectifying AC power supplied from an AC external power supply, for example, a commercial AC power supply of single-phase, 200/230 V, 50/60 Hz, in a rectifier circuit such as a full-wave rectifier circuit, and smoothing it with a smoothing capacitor. is obtained Here, a circuit including a rectifier circuit and a smoothing capacitor (capacitor) provided on an output side of the rectifier circuit will be referred to as a power supply circuit. The start of the power circuit is made by closing the contact of the main circuit relay inserted into the conducting wire connecting the external power supply and the power circuit, for example.

A large inrush current flows when the power supply circuit is started in a state where the smoothing capacitor has not sufficiently accumulated charge. As a method of limiting the inrush current at startup, Patent Documents 1 to 3 disclose that a resistor for limiting inrush current is inserted between a rectifier circuit and a smoothing circuit in a power supply circuit, and a switch or Prepare the relay, start the power circuit with the switch or relay open, and after a certain amount of charge is accumulated in the smoothing capacitor, that is, after the smoothing capacitor is charged to some extent, the both ends of the resistor are short-circuited by the switch or relay is disclosed. Regarding the timing of short-circuiting both ends of the inrush current limiting resistor, Patent Document 1 discloses an input voltage detection circuit that detects a voltage at the junction between the output of the rectifier circuit and the inrush current limiting resistor, and the charging voltage of the smoothing capacitor. A charging voltage detection circuit for detection is provided, and the resistance is short-circuited based on a comparison of a predetermined value with a difference in voltage detected by both detection circuits. Patent Document 3 discloses that both ends of the inrush current limiting resistor are short-circuited when a predetermined delay time elapses after the charging voltage of the smoothing capacitor reaches a predetermined value.

Japanese Patent Laid-Open No. 3-27721 Japanese Patent Laid-Open No. 3-22867 Japanese Patent Laid-Open No. 62-166779

In the techniques disclosed in Patent Documents 1 to 3, even if there is no need to limit the inrush current, there are cases in which both ends of the resistor for limiting the inrush current are still not short-circuited. For example, when the voltage of AC power input to the power supply circuit is lowered, since the inrush current itself is also small, it is possible to short-circuit both ends of the inrush current limiting resistor earlier. cannot respond to such cases. Similarly, when the power supply circuit is started with a voltage remaining in the smoothing capacitor, the smoothing capacitor is charged early, but the techniques disclosed in Patent Documents 1 to 3 cannot cope with such a case. When a motor is provided as a load of the power supply circuit, in order to avoid the effect of voltage drop in the inrush current limiting resistor and to avoid excessive heat generation of this resistor, short-circuit both ends of the inrush current limiting resistor. After that, it is common for the motor to start. Therefore, if the timing of short-circuiting both ends of the inrush current limiting resistor is unnecessarily delayed, the timing of starting the motor is also delayed by that much.

An object of the present invention is to provide an inrush current limiting circuit and a method for limiting inrush current that enable the motor to be started earlier after the power supply circuit is started while limiting the inrush current in the power supply circuit for driving the motor. is in doing

The inrush current limiting circuit of the present invention has a rectifier circuit to which AC power is supplied from an external power source and a smoothing capacitor provided on the output side of the rectifier circuit, and limits the inrush current in a power supply circuit used for driving a motor. A circuit, comprising: a short circuit relay having a resistor inserted between the input of an external power supply and a power supply circuit, and a contact capable of shorting both ends of the resistor; A first voltage detector that detects a voltage, a second voltage detector that detects the charging voltage of the smoothing capacitor, and a contact of the short circuit relay based on the detection result of the first voltage detector and the detection result of the second voltage detector and control means for performing control to change from open to closed.

Whether the smoothing capacitor provided on the output side of the rectifier circuit is sufficiently charged, that is, whether the inrush current limiting resistor provided on the input side of the rectifier circuit may be short-circuited depends on the peak value in the AC power supplied to the rectifier circuit. It can be judged by whether the charging voltage of the smoothing capacitor is sufficiently close to the In the inrush current limiting circuit of the present invention, the voltage of the AC voltage supplied from the external power source to the power supply circuit is measured by the first voltage detector, the charging voltage of the smoothing capacitor is measured by the second voltage detector, and based on these measurement results Since both ends of the resistor for limiting inrush current are short-circuited based on the basis, both ends of the resistor can be short-circuited at the shortest timing regardless of the voltage fluctuation of the supplied AC power, and with this, the motor that is the load of the power circuit You can speed up the start timing of

In the inrush current limiting circuit of the present invention, when the first voltage detector has a function of detecting the waveform of AC power, and performs control to short-circuit the inrush current limiting resistor by means of a short circuit relay, the first voltage detector Based on the detection result in , it is possible to control to close the contact of the short circuit relay in synchronization with the zero cross point in the waveform of the AC power. In this configuration, since the contact point of the short-circuit relay is closed at the timing in the vicinity of the zero-crossing point, the current flowing through the contact point at the moment of closing the contact point becomes small, and wear and tear of the contact point can be suppressed.

In the inrush current limiting circuit of the present invention, when a main circuit relay for supplying and blocking AC power from an external power supply to the power supply circuit is provided between the inrush current limiting resistor and the external power supply, the first voltage detector is the main It may be provided on the side of an external power supply rather than a circuit relay. By providing the first voltage detector on the side of the external power supply rather than the main circuit relay, it becomes possible to control the main circuit relay according to the detection result by the first voltage detector. For example, the main circuit relay is made controllable by the control means, so that when the control means is about to start supplying AC power to the power supply circuit, the first voltage detector is detected with the contact of the short circuit relay open. Based on the result, it is possible to control the main circuit relay so that the contact of the main circuit relay is closed in synchronization with the zero cross point in the waveform of the AC power. When the main circuit relay is controlled in this way, the contact of the main circuit relay is closed at the timing near the zero-cross point, so the current flowing through the contact at the moment of closing the contact is reduced, and the contact wear of the main circuit relay is suppressed. can

In the inrush current limiting circuit of the present invention, after the control means performs control to change the contact of the short circuit relay to closed, the control means may notify the motor control means for controlling the drive of the motor that the motor can be started. Since the motor control means knows that the inrush current limiting resistor is short-circuited by this notification, the motor can be started immediately after the resistor is short-circuited, and the time until the motor starts can be shortened.

The inrush current limiting method of the present invention has a rectifier circuit to which AC power is supplied from an external power source and a smoothing capacitor provided on the output side of the rectifier circuit, and limits the inrush current in a power supply circuit used for driving a motor. A method, wherein the voltage of the AC power supplied to the power circuit is detected at a position closer to the external power source than the resistor inserted between the external power supply and the input of the power circuit, the charging voltage of the smoothing capacitor is detected, and the detected AC power is Based on the voltage and the charging voltage, control to short-circuit the resistor is performed.

In the inrush current limiting method of the present invention, since both ends of the inrush current limiting resistor are short-circuited based on the voltage of the AC voltage supplied from the external power source to the power supply circuit and the charging voltage of the smoothing capacitor, the voltage of the supplied AC power varies Regardless, both ends of the inrush current limiting resistor can be short-circuited at the shortest timing, and with this, the start timing of the motor serving as the load of the power circuit can be accelerated.

In the inrush current limiting method of the present invention, when the voltage of the AC power is detected, the waveform of the AC power is also detected, and when the control for short-circuiting the inrush current limiting resistor is performed, it is synchronized with the zero cross point in the waveform of the AC power. Thus, it is possible to control that the contact of the short circuit relay that shorts both ends of the resistor is closed. If the control is performed in this way, since the contact of the short-circuit relay is closed at the timing in the vicinity of the zero-crossing point, the current flowing through the contact at the moment of closing the contact is reduced, and wear and tear of the contact can be suppressed.

Further, in the inrush current limiting method of the present invention, when a main circuit relay for supplying and interrupting AC power from an external power source to the power circuit is provided between the measuring points of the inrush current limiting resistance and voltage, the power circuit Control can be performed so that the contact of the main circuit relay is closed in synchronization with the zero-crossing point in the waveform of the AC power while the contact of the short circuit relay is left open when starting the supply of AC power. When the main circuit relay is controlled in this way, the contact of the main circuit relay is closed at the timing in the vicinity of the zero-crossing point, so the current flowing through the contact at the moment of closing the contact is reduced, and wear and tear of the contact of the main circuit relay is suppressed. can do.

In the inrush current limiting method of the present invention, after controlling to short-circuit the inrush current limiting resistor, the motor control means for controlling the driving of the motor may be notified that the motor can be started. By receiving such a notification, the motor control means can start the motor immediately after the resistor is short-circuited, and can shorten the time until the start of the motor.

According to the present invention, it is possible to obtain an inrush current limiting circuit and an inrush current limiting method that enable the motor to be started earlier after the power supply circuit is started while limiting the inrush current in the power supply circuit for driving the motor. have.

1 is a block diagram showing the configuration of an inrush current limiting circuit according to an embodiment of the present invention.
FIG. 2 is a timing chart for explaining the operation of the inrush current limiting circuit shown in FIG. 1. FIG.

EMBODIMENT OF THE INVENTION Next, embodiment of this invention is described with reference to drawings. 1 shows the configuration of an inrush current limiting circuit according to an embodiment of the present invention. In the illustrated circuit, a power supply circuit 15 to which AC power is supplied from an external power source, for example, an AC power supply 10 that is a commercial power supply is provided, and the power supply circuit 15 has full-wave rectification for rectifying the supplied AC power. A circuit 16 and a smoothing capacitor 17 for smoothing the pulsating current output from the full-wave rectifying circuit 16 are provided. The power supply circuit 15 is provided in order to output DC power and drive the motor 32 of each axis of an industrial robot, for example. In the example shown, the DC power obtained by the power supply circuit 15 is a short circuit protection fuse. Via 18, it is supplied to the servo driver 31 that drives the motor 32 and controls the servo. The servo driver 31 drives the motor 32 using the DC power supplied in response to a command from the motor control unit 30 that performs drive control of the motor 32 based on an external command.

Between the AC power supply 10 and the power supply circuit 15, a main circuit relay 12 for supplying and interrupting AC power from the AC power supply to the power supply circuit 15 is provided. In the industrial robot, the motor 32 should not be driven unless a predetermined condition for safety is met, so the main circuit relay 12 is a safety judgment circuit (shown in the figure) that determines whether or not a predetermined condition for safety is satisfied. The contact is closed according to the safety output signal from ) to supply the AC power from the AC power supply 10 to the power supply circuit 15 . The safety output signal is applied to the coil 12a of the main circuit relay 12 via a delay element 21 which imparts a predetermined delay time. Between the main circuit relay 12 and the power supply circuit 15, a resistor 13 is provided in order to limit the inrush current flowing through the smoothing capacitor 17 when the power supply circuit 15 is started, and the resistor ( A short-circuit relay 14 having a contact for short-circuiting both ends of 13) is provided. Moreover, the AC voltage detector 11 which measures the voltage of the AC power supplied to the power supply circuit 15 from the AC power supply 10 is provided in the position closer to the AC power supply 10 rather than the main circuit relay 12. On the load side (the side of the servo driver 31 in the example shown) rather than the short-circuit protection fuse 18, a DC voltage detector 19 for measuring the output voltage of the power supply circuit 15, that is, the charging voltage of the smoothing capacitor 17 is provided. is provided. The AC voltage detector 11 and the DC voltage detector 12 correspond to a 1st voltage detector and a 2nd voltage detector, respectively.

In general, when starting the power supply circuit 15, the contact of the short circuit relay 14 is closed while the contact of the short circuit relay 14 is open. Then, the AC power from the AC power supply 10 is supplied to the power supply circuit 15 via the inrush current limiting resistor 13, and the charging voltage of the smoothing capacitor 17 rises. After that, when the smoothing capacitor 17 is sufficiently charged, the contact of the short-circuit relay 14 is closed, so that the AC power from the AC power supply 10 does not pass through the inrush current limiting resistor 13 and the short-circuit relay 14 to be supplied to the power circuit 15 through the contact of That the smoothing capacitor 17 is sufficiently charged means that the forward voltage drop in the full-wave rectifier circuit 16 is negligible, and the smoothing capacitor 17 is compared to the peak value of the AC power supplied to the power supply circuit 15 . ) means that the charging voltage is sufficiently close. If there is a voltage fluctuation on the side of AC power, the charging voltage in the sufficiently charged state of the smoothing capacitor 17 also varies, so only paying attention to the charging voltage of the smoothing capacitor 17 is enough ( It is not possible to determine whether 17) has been sufficiently charged.

Therefore, the inrush current limiting circuit of the present embodiment is controlled to change the contact point of the short circuit relay 14 from open to closed based on the detection result by the AC voltage detector 11 and the detection result by the DC voltage detector 19 . It is provided with the control part 20 which performs. The control unit 20 is constituted by, for example, a CPU (central processing unit) or a microprocessor, and corresponds to a control means. More specifically, the control unit 20 obtains the peak value of the AC power from the voltage value detected by the AC voltage detector 11 , and the charging voltage and the peak height of the smoothing capacitor 17 detected by the DC voltage detector 19 . The coil 14a of the short circuit relay 14 is driven so that the contact of the short circuit relay 14 may be closed when the difference of values becomes below a predetermined threshold value. When closing the contact of the short circuit relay 14, the contact of the main circuit relay 12 is already closed, and it is necessary that AC power is supplied to the power supply circuit 15. As shown in FIG. 1, the AC voltage detector 11 is provided on the AC power supply 10 side rather than the main circuit relay 12, and even if the contact of the main circuit relay 12 is open, the AC voltage detector 11 detects a voltage, it cannot be judged whether or not AC power is really being supplied to the power supply circuit 15 based on the detection result of the AC voltage detector 11 . So, in the circuit shown in Fig. 1, the safety output signal is supplied to the control unit 20 through the delay element 21, and it is checked whether AC power is being supplied to the power supply circuit 15 through the main circuit relay 12. Based on the safety output signal, the control unit 20 is allowed to determine.

Fig. 2 is a timing chart showing the operation of the inrush current limiting circuit according to the present embodiment. It is assumed that the power circuit 15 is for driving the motor 32 of each axis of the industrial robot and is provided in a robot controller (not shown) used to control the robot. In the initial state, the contacts of the main circuit relay 12 and the short circuit relay 14 are open. In this initial state, the AC power supply 10 itself is operating, and in the figure, the AC input voltage is supplied from the AC power supply 10 detected by the AC voltage detector 11 toward the power supply circuit 15 . It represents the voltage of AC power. In addition, when there is a residual voltage in the smoothing capacitor 15, the charging voltage of the smoothing capacitor 15 in an initial state does not become 0V.

In order to operate the robot, first, a servo ON command is input to the robot controller. The input of the servo ON command is indicated in the figure by the command transitioning from OFF to ON. When a servo ON command is input, a safety judgment circuit (not shown) in the robot controller determines whether a predetermined condition for safety is satisfied, and if the condition is satisfied, turns the safety output signal from OFF to ON and outputs a safety output output a signal. As a result, the contact of the main circuit relay 12 changes from OFF (open) to ON (closed) after a delay time by the delay element 21 . At this point, the contact of the short circuit relay 14 remains open, and the AC power from the AC power supply 10 is supplied to the power supply circuit 15 through the inrush current limiting resistor 13 . The DC output voltage of the power supply circuit 15, that is, the charging voltage of the smoothing capacitor 17 gradually rises. And when this charging voltage fully approaches the voltage of AC power represented by the peak value, the control part 20 controls the contact of the short circuit relay 14 from open to close.

In the inrush current limiting circuit of this embodiment, based on the voltage of the AC power supplied from the AC power supply 10 to the power supply circuit 15 and the charging voltage of the smoothing capacitor 17, the AC power voltage peak value is charged. When the voltage approaches sufficiently, both ends of the resistor 13 are short-circuited by the short-circuit relay 14 . As a result, both ends of the inrush current limiting resistor 13 can be short-circuited in a short time regardless of voltage fluctuations on the AC power supply 10 side, and the time from the start of the power supply circuit 15 to the start of the motor 32 . It becomes possible to shorten

It is assumed that the motor 32 is controlled by the motor control unit 30 via the servo driver 31 , and the motor control unit 30 controls the start of the motor 32 . As a more specific configuration for shortening the time until the start of the motor 32 , the control unit 20 determines that the motor 32 can be started when the short circuit relay 14 is controlled to be closed. ) can be notified. When the motor control unit 30 receives this notification and starts the motor 32 , the time from the start of the power supply circuit 10 to the start of the motor 32 can be made shorter. In addition, the motor control part 30 which performs drive control of the motor 32 based on an external command is comprised by a CPU or a microprocessor, for example.

In the case of using an AC voltage detector 11 capable of detecting a waveform of AC power, the control unit 20 detects a zero cross point in the AC power waveform and synchronizes with the cell cross point. It is preferable to drive the coil 14a of the short-circuit relay 14 so as to close the contact of the short-circuit relay 14 at a timing in the vicinity of . By closing the contact point of the short circuit relay 14 at the timing in the vicinity of the zero-cross point in the waveform of AC power, the current flowing through the contact point at the moment of closing the contact point becomes small, so that wear and tear of the contact point can be reduced.

As described above, the main circuit relay 12 is controlled to close the contact by the safety output signal. Since the safety control signal is also supplied to the control unit 20, when an AC voltage detector 11 capable of detecting a waveform of AC power is used, the main circuit relay 12 is controlled by the safety output signal itself. Instead of controlling, the control unit 20 may perform control to close the contact of the main circuit relay 12 at a timing that is synchronized with the zero-cross point of the waveform of the AC power while the safety output signal is output. By closing the contact point of the main circuit relay 12 at the timing in the vicinity of the zero cross point in the waveform of AC power, the current flowing through the contact point at the moment of closing the contact point becomes small, so the contact point of the main circuit relay 12 It can reduce wear and tear.

10: AC power
11: AC voltage detector
12: main circuit relay
13: resistance
14: short circuit relay
15: power circuit
16: full-wave rectification circuit
17: smoothing capacitor
18: short circuit protection fuse
19: DC voltage detector
20: control unit
21: delay element
30: motor control unit
31: servo driver
32: motor

Claims (9)

An inrush current limiting circuit having a rectifier circuit to which AC power is supplied from an external power source and a smoothing capacitor provided on the output side of the rectifier circuit and limiting the inrush current in a power supply circuit used for driving a motor,
a resistor inserted between the external power supply and an input of the power supply circuit;
a short circuit relay having a contact capable of shorting both ends of the resistor;
a first voltage detector that detects a voltage of AC power supplied to the power supply circuit at a position closer to the external power supply than the resistor;
a second voltage detector for detecting the charging voltage of the smoothing capacitor;
and control means for performing control to change the contact point of the short circuit relay from open to closed based on a detection result by the first voltage detector and a detection result by the second voltage detector. According to claim 1,
The first voltage detector has a function of detecting a waveform of AC power,
When the control means performs control to change the contact point of the short circuit relay from open to closed, based on a detection result of the first voltage detector, the short circuit is synchronized with a zero cross point in the waveform of the AC power. An inrush current limiting circuit that controls the short circuit relay so that the contact point of the relay is closed. 3. The method of claim 2,
A main circuit relay is provided between the resistor and the external power supply to supply and cut off the AC power from the external power supply to the power supply circuit,
The first voltage detector is an inrush current limiting circuit provided on a side of the external power supply rather than the main circuit relay. 4. The method of claim 3,
the main circuit relay is controllable by the control means;
When the control means is about to start supplying the AC power to the power supply circuit, the waveform of the AC power is based on a detection result of the first voltage detector while the contact of the short circuit relay is left open. An inrush current limiting circuit for controlling the main circuit relay so that a contact of the main circuit relay is closed in synchronization with a zero cross point in 5. The method according to any one of claims 1 to 4,
The inrush current limiting circuit in which the control means performs the control of changing the contact of the short circuit relay to closed, and then notifies the motor control means for controlling the driving of the motor that the motor can be started. An inrush current limiting method for limiting the inrush current in a power supply circuit used for driving a motor having a rectifier circuit to which AC power is supplied from an external power source and a smoothing capacitor provided on the output side of the rectifier circuit,
detecting a voltage of the AC power supplied to the power supply circuit at a position closer to the external power supply than a resistor inserted between the external power supply and an input of the power supply circuit;
detecting the charging voltage of the smoothing capacitor,
The inrush current limiting method of performing control to short-circuit the resistor based on the voltage of the AC power and the charging voltage. 7. The method of claim 6,
When detecting the voltage of the AC power, the waveform of the AC power is also detected,
A method for limiting inrush current in which, when controlling to short-circuit the resistor, a contact of a short-circuit relay that shorts both ends of the resistor is closed in synchronization with a zero-crossing point in the waveform of the AC power. 8. The method of claim 7,
A main circuit relay for supplying and blocking AC power from the external power supply to the power supply circuit is provided between the resistance and the voltage measurement point of the AC power, and to start supplying AC power to the power supply circuit at this time, while leaving the contact point of the short circuit relay open, control is performed so that the contact point of the main circuit relay is closed in synchronization with a zero cross point in the waveform of the AC power. 9. The method according to any one of claims 6 to 8,
The inrush current limiting method of notifying the motor control means for controlling the driving of the motor that the start of the motor is enabled after performing the control to short-circuit the resistor.

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