JP2014233752A - Power supply device and arc processing power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that, if a step-down chopper circuit included in a power supply device is damaged, an inverter circuit is damaged to be interlocked with the step-down chipper circuit.SOLUTION: A power supply device comprises: a direct-current (DC) power supply circuit; a step-down chopper circuit provided on an output of the DC power supply circuit and formed out of a first switching element, a reactor, and a third smoothing capacitor; a main transformer converting an output from an inverter circuit to a voltage suited for a load; a secondary rectifier circuit and a DC reactor rectifying and smoothing an output from the main transformer; and a main control circuit controlling the first switching element and the inverter circuit. The rectifier circuit is a three-phase full-wave rectifier circuit formed out of three thyristor elements and three diodes. The power supply device also includes a voltage discrimination circuit that outputs a voltage discrimination signal if a step-down voltage value is equal to or higher than a voltage reference value. The main control circuit cuts off the three thyristor elements in response to the voltage discrimination signal.

Description

  The present invention relates to a power supply device including a DC power supply circuit that converts an AC power supply into a DC voltage, and a step-down chopper circuit that steps down the DC voltage to a predetermined voltage.

  In the power supply device used for arc machining, a commercial power supply (three-phase AC power supply) is rectified by a rectifier circuit, smoothed by a smoothing capacitor and converted into a DC voltage, and an inverter circuit forming a bridge with a switching element, A step-down chopper circuit for stepping down the DC voltage to an input voltage suitable for the input of the inverter circuit is provided.

  FIG. 7 is an electrical connection diagram of a conventional power supply device used for arc machining, and is formed by a DC power supply circuit, a step-down chopper circuit, an inverter circuit INV, a main transformer, a secondary rectifier circuit, and a DC reactor. In the figure, the DC power supply circuit is formed by a rectifier circuit DR1, a first smoothing capacitor C1, a second smoothing capacitor C2, a first resistor R1, and a second resistor R2.

The step-down chopper circuit shown in FIG. 7 is formed of a first switching element TR1, a reactor DL, and a third smoothing capacitor C3, and applies a DC voltage from a DC power supply circuit based on the on duty of the first switching element TR1. Step down to voltage. The voltage detection circuit IV detects the step-down voltage output from the step-down chopper circuit and outputs it as a step-down voltage signal Iv.

  The inverter circuit INV converts the step-down voltage from the step-down chopper circuit into a high-frequency AC voltage, and the main transformer INT converts the high-frequency AC voltage into a high-frequency AC voltage suitable for arc machining, and a secondary rectifier circuit DR2 and a DC reactor. It is rectified and smoothed through the DCL and power is supplied between the torch TH and the workpiece M.

  The main control circuit SC controls the inverter circuit INV so that the value of the output current detection signal Id from the output current detection circuit ID becomes a predetermined current setting value, and the step-down voltage becomes a predetermined voltage setting value. So as to control the step-down chopper circuit.

  When the first switching element TR1 forming the step-down chopper circuit shown in FIG. 7 is short-circuit broken for some reason, the step-down voltage from the step-down chopper circuit rises to form the third smoothing capacitor C3 and the inverter circuit. The maximum input voltage standard of the input voltage of each switching element is exceeded, resulting in destruction.

In order to prevent the third smoothing capacitor C3 and the inverter circuit INV from being destroyed due to the input overvoltage, the protection fuse F1 and the second switching element TR2 shown in FIG. Makes the second switching element TR2 conductive when the step-down voltage from the step-down chopper circuit exceeds a predetermined voltage, and forms a short-circuit current loop by the protective fuse F1, the first switching element TR1 and the second switching element TR2. Thus, the protective fuse F1 is melted by a short-circuit current loop to prevent the input overvoltage from being applied to the switching elements forming the third smoothing capacitor C3 and the inverter circuit INV. Patent Document 1 discloses the above-described protection technique.

JP-A-9-247927

The second switching element (bipolar transistor, IGBT, MOSFET, etc.) shown in FIG. 7 has a limit in the short-circuit withstand capability, and when the short-circuit current flows for more than a predetermined time, the open-circuit breakdown is caused. At this time, if the protective fuse is not blown before the second switching element is broken open, an input overvoltage is applied to the third smoothing capacitor C3 and each switching element forming the inverter circuit to be destroyed. The fusing time due to the short-circuit current loop of the protective fuse has component variations, and the protective fuse is often not blown before the second switching element is broken open.
Therefore, an object of the present invention is to provide a power supply device that solves the above-described problems.

  In order to solve the above-described problems, the invention described in claim 1 is a DC power supply circuit formed by a rectifier circuit and a smoothing capacitor to rectify and smooth a commercial AC power supply to obtain a DC voltage, and an output side of the DC power supply circuit. A step-down chopper circuit formed by a third smoothing capacitor arranged in series between the first switching element and the reactor in one of the two and arranged between the output side of the reactor and the other of the output side of the DC power supply circuit A voltage detection circuit that detects a step-down voltage from the step-down chopper circuit, an inverter circuit that converts the step-down voltage into a high-frequency AC voltage, and a main transformer that converts the output of the inverter circuit into a high-frequency AC voltage suitable for a load A secondary rectifier circuit for rectifying the output of the main transformer, a DC reactor for smoothing the rectified output, the first switching element and the front And a main control circuit that controls the inverter circuit, wherein the rectifier circuit is a three-phase full-wave rectifier circuit formed by three thyristor elements and three diodes, and the step-down voltage value is predetermined. The power supply device includes a voltage discrimination circuit that outputs a voltage discrimination signal when a voltage reference value is exceeded, and the main control circuit shuts off the three thyristor elements according to the voltage discrimination signal.

According to a second aspect of the present invention, a protective fuse is disposed between one output side of the DC power supply circuit and the input side of the first switching element, and a connection point between the first switching element and the reactor. And a second switching element between the DC power supply circuit and the other output side of the DC power supply circuit, and the main control circuit shuts off the three thyristor elements in response to the voltage determination signal and the second switching element. The power supply device according to claim 1, wherein the element is conducted.

  According to a third aspect of the present invention, the main control circuit conducts the second switching element when the value of the step-down voltage exceeds a predetermined second voltage reference value lower than the voltage reference value, and The power supply device according to claim 2, wherein the three thyristor elements are cut off according to a voltage determination signal.

  The power supply device according to any one of claims 1 to 3, wherein the rectifier circuit is a three-phase half-wave rectifier circuit formed by the three thyristor elements. It is.

  Invention of Claim 5 is comprised so that the voltage for arc processing which performs arc processing of a workpiece may be produced | generated using the power supply device of any one of Claims 1-4. It is a power supply device for arc processing.

According to the first aspect of the present invention, when an abnormality occurs in the step-down chopper circuit, the three thyristor elements forming the rectifier circuit are cut off, so that the step-down chopper circuit is included in each switching element forming the third smoothing capacitor and the inverter circuit. Therefore, it is possible to suppress the application of an overvoltage and prevent destruction.

According to the second and third aspects of the present invention, when an abnormality occurs in the step-down chopper circuit, the rectifier circuit is provided even when the second switching element is broken by a short-circuit current and the protection coordination cannot be obtained before the protective fuse is blown. Since the three thyristor elements to be formed are cut off, application of an overvoltage from the step-down chopper circuit to each switching element forming the third smoothing capacitor and the inverter circuit can be suppressed and destruction can be prevented.

  In the invention according to claim 4, even the three-phase half-wave rectifier circuit formed by the rectifier circuit with three thyristor elements has the same effect as the invention according to claims 1-3.

In the invention according to claim 5, an abnormality occurs in the step-down chopper circuit regardless of whether the rectifier circuit used in the arc machining power supply device is a three-phase full-wave rectifier circuit or a three-phase half-wave rectifier circuit formed by three thyristor elements. Then, by blocking the three thyristor elements, it is possible to suppress the overvoltage from being applied from the step-down chopper circuit to the switching elements forming the third smoothing capacitor and the inverter circuit, and to prevent the breakdown.

It is an electrical connection figure of the power supply device which concerns on Embodiment 1 of this invention. 2 is a detailed diagram of a voltage determination circuit according to the first embodiment. FIG. FIG. 6 is a waveform diagram for explaining the operation of the first embodiment. 6 is an electrical connection diagram of a power supply device according to Embodiment 2. FIG. FIG. 6 is a waveform diagram for explaining the operation of the second embodiment. FIG. 6 is an electrical connection diagram of a power supply device according to a third embodiment. It is an electrical connection diagram of the power supply device of a prior art.

The operation of the first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is an electrical connection diagram of a power supply device (for example, a power supply device for arc machining) according to Embodiment 1 of the present invention. In the figure, components having the same reference numerals as those in the electrical connection diagram of the prior art power supply device shown in FIG. 7 perform the same operations, and thus description thereof will be omitted. Only components having different reference numerals will be described.

  The rectifier circuit shown in FIG. 1 is a three-phase full-wave rectifier circuit formed by three thyristor elements SR1 to SR3 and three diodes D1 to D3. For example, thyristor integration in which three thyristor elements are integrated in one package. The circuit may be formed of a diode integrated circuit in which three diodes are integrated in one package.

  FIG. 2 is a detailed diagram of the voltage discriminating circuit IM, which is formed by a comparator CP and a voltage reference setting circuit VREF. When the value of the step-down voltage signal Iv is equal to or higher than a predetermined voltage reference value Vref, FIG. The voltage determination signal Im is set to a high level. The value of the voltage reference value Vref at this time corresponds to, for example, the maximum rating of the input voltage of each switching element that forms the inverter circuit INV.

The main control circuit SC shown in FIG. 1 controls the inverter circuit INV so that the value of the output current detection signal Id from the output current detection circuit ID becomes a predetermined current set value, and the value of the step-down voltage signal Iv is set in advance. The step-down chopper circuit is controlled so that the set voltage is set. When the voltage determination signal Im becomes High level, the three thyristor elements SR are shut off. At this time, the operation of the inverter circuit INV may be stopped.

FIG. 3 is a waveform diagram for explaining the operation of the first embodiment.
3A shows the voltage waveform of the commercial AC power supply, FIG. 3B shows the thyristor drive signal Sr, FIG. 3C shows the voltage determination signal Im, and FIG. (D) shows the DC voltage waveform V1, FIG. 6 (E) shows the waveform of the step-down voltage signal Iv, FIG. 4 (F) shows the waveform of the first switching drive signal Tr1, and FIG. G) shows the waveform of the output current signal Id.

Next, the operation of the power supply apparatus according to the first embodiment will be described with reference to FIGS.
Before time t = t1 shown in FIG. 3, the main control circuit SC controls the inverter circuit INV so that the value of the output current detection signal Id becomes a predetermined current set value. Then, after time t = t1, when the first switching element TR1 forming the step-down chopper circuit is short-circuit broken for some reason, the voltage detection circuit IV detects the step-down voltage signal Iv as shown in FIG. The value rises.

  When the value of the step-down voltage signal Iv becomes equal to or higher than a predetermined voltage reference value Vref at time t = t3, the comparator CP shown in FIG. 2 sets the voltage determination signal Im to the high level. The main control circuit SC sets the thyristor drive signal Sr shown in FIG. 3B to a low level in accordance with the high level of the voltage determination signal Im. The three thyristor elements SR1 to SR3 shown in FIG. 1 are extinguished according to the low level of the thyristor drive signal Sr, and the first thyristor element SR1 extinguishes when the U phase of the commercial AC power supply becomes zero voltage, and the second thyristor The element SR2 extinguishes when the W phase becomes zero voltage, and the third thyristor element SR3 extinguishes when the V phase becomes zero voltage, and the value of the DC voltage waveform V1 shown in FIG. Become.

  From the above, when the first switching element TR1 that forms the step-down chopper circuit is broken down, the three thyristor elements that form the rectifier circuit are shut off, so that each of the third smoothing capacitor C3 and the inverter circuit is formed. It can suppress that the input voltage of a switching element exceeds a maximum rating, and can prevent the destruction by the application of an overvoltage.

“Embodiment 2”
Next, the operation of the second embodiment will be described with reference to FIG.
FIG. 4 is an electrical connection diagram of the power supply device (arc machining power supply device) according to the second embodiment. In the same figure, components having the same reference numerals as those in the electrical connection diagrams of the power supply apparatus shown in FIGS. 1 and 7 perform the same operations, and thus description thereof will be omitted. Only components having different reference numerals will be described.

  A protective fuse F1 is disposed between one output side (plus side) of the DC power supply circuit shown in FIG. 4 and the input side of the first switching element TR1, and a connection point between the first switching element TR1 and the reactor DCL. And the other output side (minus side) of the DC power supply circuit, the second switching element TR2 is arranged to form a protection circuit.

The voltage determination circuit IM shown in FIG. 4 sets the voltage determination signal Im to a high level when the value of the step-down voltage signal Iv is equal to or higher than the voltage reference value Vref.

The main control circuit SC shown in FIG. 4 controls the inverter circuit INV so that the value of the output current detection signal Id from the output current detection circuit ID becomes the current set value, and the value of the step-down voltage signal Iv becomes the voltage set value. The step-down chopper circuit is controlled as follows. Then, the thyristor drive signal Sr is set to the Low level and the second switching drive signal Tr2 is set to the High level according to the High level of the voltage determination signal Im.
The main control circuit SC is provided with a predetermined second voltage reference value Vref2 in which the value of the step-down voltage signal Iv is lower than the voltage reference value vref. When the voltage becomes equal to or higher than the second voltage reference value Vref2, the second switching drive signal is provided. Tr2 may be set to a high level.

FIG. 5 is a waveform diagram for explaining the operation of the second embodiment.
5A shows the voltage waveform of the commercial AC power supply, FIG. 5B shows the thyristor drive signal Sr, FIG. 5C shows the voltage determination signal Im, and FIG. (D) shows the DC voltage waveform V1, FIG. 6 (E) shows the waveform of the step-down voltage signal Iv, FIG. 4 (F) shows the waveform of the first switching drive signal Tr1, and FIG. G) shows the waveform of the second switching drive signal Tr2, and (H) shows the waveform of the output current signal Id.

Next, the operation of the power supply apparatus according to the second embodiment will be described with reference to FIGS. 4 and 5.
Before time t = t1 shown in FIG. 5, the main control circuit SC controls the inverter circuit INV so that the value of the output current detection signal Id becomes the current set value. At time t = t1, when the first switching element TR1 forming the step-down chopper circuit breaks down for some reason, the value of the step-down voltage signal Iv increases in FIG. 5E detected by the voltage detection circuit IV. To do.

  When the value of the step-down voltage signal Iv becomes equal to or higher than the voltage reference value vref at time t = t3, the voltage determination circuit IM sets the voltage determination signal Im shown in FIG. 5C to a high level. The main control circuit SC sets the second switching drive signal Tr2 shown in FIG. 5G to the high level in accordance with the high level of the voltage determination signal Im, and turns on the second switching element TR2. At this time, the protective fuse F1, the first switching element TR1 and the second switching element TR2 form a short-circuit current loop, the protective fuse F1 is blown by the short-circuit current, and the value of the step-down voltage signal Iv is suppressed from rising. Decrease. However, if the second switching element TR2 is broken open before the protective fuse F1 is blown, the value of the step-down voltage signal Iv shown in FIG. 5E changes from decreasing to increasing at time t = t4.

  At time t = t3, the main control circuit SC also sets the thyristor drive signal Sr shown in FIG. 5B to the low level in accordance with the high level of the voltage determination signal Im. The three thyristor elements SR1 to SR3 shown in FIG. 4 are extinguished according to the low level of the thyristor drive signal Sr, and the first thyristor element SR1 extinguishes when the U phase of the commercial AC power supply becomes zero voltage, and the second thyristor The element SR2 extinguishes when the W phase becomes zero voltage, and the third thyristor element SR3 extinguishes when the V phase becomes zero voltage, and the value of the DC voltage waveform V1 shown in FIG. Furthermore, it turns to decrease and becomes zero.

As described above, even when the protective fuse is not blown, the three thyristor elements forming the rectifier circuit are shut off, so that an overvoltage may be applied from the step-down chopper circuit to each switching element forming the third smoothing capacitor and the inverter circuit. It can be suppressed and destruction can be prevented.

  In the second embodiment, the main control circuit SC sets the second switching drive signal Tr2 shown in FIG. 5 (G) to the high level according to the high level of the voltage determination signal Im and also shows the same in FIG. Although the thyristor drive signal Sr shown is at a low level, the main control circuit SC is provided with a predetermined second voltage reference value Vref2 lower than the voltage reference value Vref, and at time t = t2, the value of the step-down voltage signal Iv is When the voltage becomes equal to or higher than the second voltage reference value Vref2, the second switching drive signal Tr2 may be set to a high level as indicated by a dotted line.

As a result, the second switching element TR2 shown in FIG. 4 becomes conductive before the three thyristor elements forming the rectifier circuit are shut off, and thus the protective fuse F1, the first switching element TR1, and the second switching element TR2 Thus, the short-circuit current loop is formed first, and an appropriate time for fusing the protective fuse F1 by the short-circuit current loop can be obtained, so that the protective fuse can be prevented from being blown, and accurate protection coordination can be achieved.

“Embodiment 3”
Next, the operation of the third embodiment will be described with reference to FIG.
FIG. 6 is an electrical connection diagram of the power supply device (arc machining power supply device) according to the third embodiment. In the figure, components having the same reference numerals as those in the electrical connection diagrams of the power supply apparatus shown in FIGS. 1, 4 and 5 perform the same operations, and thus description thereof will be omitted. Only components having different reference numerals will be described.

  The rectifier circuit shown in FIG. 6 forms a three-phase half-wave rectifier circuit with three thyristor elements SR1 to SR3, and the main control circuit SC has three thyristors when the voltage discrimination signal Im from the voltage discrimination circuit IM becomes High level. The element SR is cut off and the second switching element TR2 is turned on. At this time, the operation of the inverter circuit INV may be stopped.

C1 First smoothing capacitor C2 Second smoothing capacitor C3 Third smoothing capacitor CP Comparator D1 First diode D2 Second diode D3 Third diode D4 Fourth diode DL Reactor DCL DC reactor DR2 Secondary rectification Circuit F1 Protection fuse ID Output current detection circuit Id Output current detection signal IM Voltage discrimination circuit Im Voltage discrimination signal INT Main transformer INV Inverter circuit IV Voltage detection circuit Iv Step-down voltage signal M Workpiece R1 First resistor R2 Second Resistor SC Main control circuit Sc Main control signal SR1 First thyristor element SR2 Second thyristor element SR3 Third thyristor element Sr Thyristor drive signal TR1 First switching element TR2 Second switching element TH Torch VREF Voltage reference Setting circuit Vref Voltage reference signal (voltage reference value)

Claims (5)

A DC power supply circuit formed by a rectifier circuit and a smoothing capacitor to rectify and smooth a commercial AC power supply to be a DC voltage, and a first switching element and a reactor are arranged in series on one of the output sides of the DC power supply circuit, and A step-down chopper circuit formed by a third smoothing capacitor disposed between the output side of the reactor and the other output side of the DC power supply circuit; and a voltage detection circuit for detecting a step-down voltage from the step-down chopper circuit; An inverter circuit that converts the step-down voltage into a high-frequency AC voltage, a main transformer that converts the output of the inverter circuit into a high-frequency AC voltage suitable for a load, and a secondary rectifier circuit that rectifies the output of the main transformer; A power supply comprising: a DC reactor that smoothes the rectified output; and a main control circuit that controls the first switching element and the inverter circuit The rectifier circuit is a three-phase full-wave rectifier circuit formed by three thyristor elements and three diodes, and outputs a voltage discrimination signal when the step-down voltage value is equal to or higher than a predetermined voltage reference value. A power supply apparatus comprising: a circuit, wherein the main control circuit cuts off the three thyristor elements in response to the voltage determination signal.   A protective fuse is disposed between one output side of the DC power supply circuit and the input side of the first switching element, and a connection point between the first switching element and the reactor and an output side of the DC power supply circuit A second switching element is disposed between the second switching element and the main control circuit shuts off the three thyristor elements and conducts the second switching element in response to the voltage determination signal; The power supply device according to claim 1.   The main control circuit conducts the second switching element when the value of the step-down voltage exceeds a predetermined second voltage reference value that is lower than the voltage reference value, and the main control circuit performs the operation according to the voltage determination signal. The power supply device according to claim 2, wherein one thyristor element is cut off.   The power supply apparatus according to any one of claims 1 to 3, wherein the rectifier circuit is a three-phase half-wave rectifier circuit formed by the three thyristor elements.   An arc machining power supply device configured to generate an arc machining voltage for performing arc machining on a workpiece using the power supply device according to claim 1.

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