JP5053581B2 - Arc machining power supply - Google Patents

Description

  The present invention relates to a power supply device for arc machining in which a commercial AC power supply can use either a high voltage or a low voltage of about half of the commercial AC power supply.

  In the arc machining power supply device, since the commercial AC power supply shares two power supplies of 200V or 400V, it has been dealt with by switching the turns ratio of the transformer.

  FIG. 4 is an electrical connection diagram of a conventional arc machining power supply device. In the figure, diodes D9 to D18 are primary rectifying diodes that three-phase full-wave rectify commercial AC power to DC voltage. The switches SW1 to SW3 are voltage changeover switches interlocking with each other, and the smoothing capacitor C6 and the smoothing capacitor C7 are capacitors that smooth the DC voltage.

  For example, the inverter circuit INV forms a full bridge with four switching elements (not shown). The main transformer INT converts the high frequency AC voltage suitable for arc machining and outputs it, and the secondary rectifier circuit DR1 rectifies the high frequency AC voltage into a DC voltage and outputs it.

  When the voltage selector switches SW1 to SW3 shown in FIG. 4 are on the a side, for example, 200V side (low voltage side), the voltage doubler rectifier circuit is formed by the diodes D9 to D18 and the capacitors C3 to C5. . On the other hand, when the voltage changeover switch SW1 to voltage changeover switch SW3 are on the b side, for example, 400V side (high voltage side), a three-phase full-wave rectifier circuit is formed by the diodes D9 to D18.

  Next, the operation will be described using the input waveform diagram of the commercial AC power source shown in FIG. When the voltage / voltage selector switch SW1 to SW3 shown in FIG. 4 are on the b side, for example, 400V side (high voltage side), the circuit is a normal three-phase full-wave rectifier circuit, and the description thereof is omitted. The operation when the voltage changeover switch SW1 to the voltage voltage changeover switch SW3 are on the a side and 200V side (low voltage side) will be described together with the U, V and W phase voltage waveforms of the commercial AC power supply.

  In the period T1 shown in FIG. 5, the U-phase potential is the highest and the V-phase potential is the lowest. Therefore, the capacitor C3 is charged through the diode D10 by the voltage between UV. At this time, an input terminal U, a voltage changeover switch SW3, a capacitor C5, a diode D16, an output terminal 1, a capacitor C6, a capacitor C7, an output terminal 2, a diode D15, and an input terminal V are disposed between the output terminals 1 and 2 shown in the figure. A voltage is applied in the path.

  At this time, the diode D9 and the diode D13 are reverse-biased by the capacitor C5 and the U-phase or V-phase potential and do not conduct. Here, the capacitor C5 is charged in the period of T5 before this, and the polarity is the same as the voltage between UV with the connection point of the diode D16 and the diode D17 being positive, and therefore between the output terminals 1 and 2. The sum of these voltages is applied.

  In the period of T2, the terminal voltage of the capacitor C3 is charged up to the peak value of the voltage between UV, so that this state is maintained without further charging. On the other hand, since the W-phase potential is the lowest between the output terminals 1 and 2, the sum of the voltage between WUs and the terminal voltage of the capacitor C5 is output through the diode D18.

  During the period T3, the V-phase potential is the highest and the W-phase potential is the lowest, so the capacitor C4 is charged by the voltage between VW, and at the same time, the sum of the voltage of the capacitor C3 and the voltage between VW is the output terminals 1, 2 Output in between.

  During the period T4, the charging of the capacitor C4 is stopped, and the sum of the terminal voltage of the capacitor C4 and the voltage between VU is output between the output terminals 1 and 2.

  During the period T5, the capacitor C5 is charged by the voltage between the WUs, and the sum of the terminal voltage of the capacitor C4 and the voltage between the WUs is output between the output terminals 1 and 2.

  During the period T6, the charging of the capacitor C5 is stopped, and the sum of the terminal voltage of the capacitor C4 and the voltage between WV is output between the output terminals 1 and 2.

In each period in which the above-described periods T1 to T6 are repeated, the terminal voltage of each capacitor is always the same polarity, and the output terminal 1 side has a positive polarity. An output voltage that is twice the voltage is supplied.
(For example, Patent Document 1)

JP-A-5-96372

  In the conventional arc machining power supply device, since the commercial AC power supply shares two power supplies of 200V or 400V, the voltage change-over switches SW1 to SW3 shown in FIG. 4 are set to the a side, for example, the 200V side (low voltage side). Sometimes nine diodes and three capacitors form a voltage doubler rectifier circuit. This three-phase full-wave rectifier circuit doubles the rectified DC voltage by three-phase full-wave rectification of 200V of commercial AC power supply. And output. On the other hand, when the voltage changeover switches SW1 to SW3 are on the b side, for example, 400V side (high voltage side), a three-phase full-wave rectifier circuit is formed by nine diodes. 400V was rectified by three-phase full-wave rectification and output, so that two power sources could be shared.

  However, in the voltage doubler rectifier circuit, it is necessary to newly provide components such as a diode having a large capacity, a capacitor, and a voltage changeover switch in each phase of the U phase, the V phase, and the W phase. Has become complicated and hinders downsizing of the power supply.

  Therefore, the present invention is to provide a power supply device for arc machining that can solve the above-described problems.

In order to solve the above-described problem, the first invention provides a three-phase full-wave rectifier circuit that outputs a pulsating DC voltage by rectifying a commercial AC power supply, and is provided in parallel with the three-phase full-wave rectifier circuit. A series circuit composed of a first smoothing capacitor and a second smoothing capacitor having the same capacity for smoothing the DC voltage, an output control circuit for controlling the output of the inverter circuit, and a main transformer for converting to a high-frequency AC voltage suitable for arc machining And a secondary rectifier circuit that rectifies the output of the main transformer and outputs a DC voltage, in the arc machining power supply device, in the plus side of the three-phase full-wave rectifier circuit and in the series circuit Between the first switching element for supplying the DC voltage to the second smoothing capacitor and the negative side of the three-phase full-wave rectifier circuit and the middle point of the series circuit. Provide the DC voltage A second charging switching element to be supplied to the first smoothing capacitor, and a discharge of the first smoothing capacitor provided between the collector side of the first charging switching element and the plus side of the series circuit. A first discharge prevention diode for preventing discharge, and a second discharge capacitor provided between the emitter side of the second charging switching element and the negative side of the series circuit for preventing discharge of the second smoothing capacitor. An anti-discharge diode, an input voltage detection circuit that detects the three-phase full-wave rectified DC voltage and outputs it as an input voltage detection signal; and a value of the input voltage detection signal is greater than or equal to a predetermined input reference value in advance wherein when more than the reference voltage value determined commercial AC power source is determined to be a 200V system, a first charge control signal and the second charge system of the same time of the maximum conduction ratio is shifted by a half cycle from each other Signals repeatedly output to conducting the first charge switching element and the second charge switching element, the commercial AC power supply when the value is more than the reference voltage value of the input voltage detection signal is a 400V system And a charging control circuit that stops the output of the first charging control signal and the second charging control signal and shuts off the first charging switching element and the second charging switching element. This is a power supply device for arc machining.

The second invention is characterized in that output frequencies of the first charge control signal and the second charge control signal of the charge control circuit are in the range of 360 Hz to 30 KHz . This is a power supply device for arc machining.

  According to the first invention, the voltage doubler rectifier circuit is formed of the first charging switching element, the second charging switching element, the first smoothing capacitor, and the second smoothing capacitor. Since the first smoothing capacitor and the second smoothing capacitor serve both as boosting and smoothing of the pulsating DC voltage, the circuit configuration becomes very simple, and the power supply device can be miniaturized.

  According to the second invention, the output frequency of the charge control circuit is set to be higher than the pulsation frequency (for example, 360 Hz) when the commercial AC power supply is three-phase full-wave rectified, and the first smoothing capacitor and the second Since the smoothing capacitor is charged, the ripple value of the charging current of the capacitor is reduced by increasing the frequency, and the life of the smoothing capacitor is extended.

  According to the third aspect of the present invention, the charging control circuit includes a rectified DC voltage and a reference voltage when a predetermined time elapses from when commercial AC power is turned on and rectification of the commercial AC power is started. Therefore, it is possible to accurately determine whether the input voltage of the commercial AC power supply is 200V or 400V.

  FIG. 1 shows an arc machining power supply apparatus according to Embodiment 1 of the present invention. In the figure, the components having the same reference numerals as those in the electrical connection diagram of the arc machining power supply device of the prior art shown in FIG. 4 perform the same operations, so the description thereof will be omitted, and only the components having different reference numerals will be described.

  A three-phase full-wave rectification circuit is formed by three-phase full-wave rectification of a three-phase commercial AC power supply by the first diode D1 to the sixth diode D6 shown in FIG. Further, a DC power supply circuit may be formed by providing a parallel capacitor of a three-phase full-wave rectifier circuit, and a DC power supply circuit may be used instead of the three-phase full-wave rectifier circuit. The input voltage detection circuit IV detects a DC voltage that has undergone three-phase full-wave rectification and outputs it as an input voltage detection signal Iv. The first smoothing capacitor C1 and the second smoothing capacitor C2 form a series circuit having the same capacity to smooth the DC voltage.

  The first charging switching element TR1 and the second charging switching element TR2 repeat the conduction and the interruption alternately for the same time without overlapping each other, so that the DC voltage from the three-phase full-wave rectifier circuit is the first. Are alternately supplied to the smoothing capacitor C1 and the second smoothing capacitor C2.

  The first discharge preventing diode D7 and the second discharge preventing diode D8 prevent the charged voltage of the charged first smoothing capacitor C1 and second smoothing capacitor C2 from being discharged.

Although the inverter circuit INV uses a full bridge circuit formed by four switching elements, a half bridge circuit or a forward circuit may be used.

  The output current detection circuit ID detects the output current and outputs it as an output current detection signal Id. The comparison operation circuit ER compares and calculates the output current setting signal Ir and the output current detection signal Id, and outputs the comparison operation signal Er. The output control circuit SC performs PWM control that modulates the pulse width with a constant pulse frequency, and sets the pulse widths of the first output control signal Sc1 and the second output control signal Sc2 according to the value of the comparison calculation signal Er. Control.

  FIG. 2 is a detailed diagram of the charge control circuit CR. The first comparison circuit CP1, the second comparison circuit CP2, the input reference setting circuit VR1, the reference voltage setting circuit VR2, the first AND circuit AD1, and the second AND circuit. The circuit AD2, the time limit circuit TI, the inverting circuit IN, and the switching element driving circuit SD are formed.

  FIG. 3 is a waveform diagram for explaining the operation of the arc machining power supply device of the present invention. The waveform in FIG. 3A shows the input voltage detection signal Iv, the waveform in FIG. 3B shows the first comparison signal Cp1 shown in FIG. 2, and the waveform in FIG. 3C shows the AND signal shown in FIG. 3 (D) shows the first charge control signal Tr1, the waveform of FIG. 3 (E) shows the second charge control signal Tr2, and the waveform of FIG. 3 (F) shows the signal Ad2. The voltage obtained by adding the voltages across the terminals of the first smoothing capacitor C1 and the second smoothing capacitor C2 is shown.

Next, the operation when the commercial AC power supply is a 200V system will be described.
When a magnet switch or the like (not shown) is turned on, the commercial AC power supply is rectified and converted into a pulsating DC voltage when it is input to the three-phase full-wave rectifier circuit. The input voltage detection circuit IV detects a pulsating DC voltage and outputs it as an input voltage detection signal Iv shown in FIG.

  At time t = t1 shown in FIG. 3, the first comparison circuit CP1 shown in FIG. 2 compares the input reference value Vr1 set by the input reference setting circuit VR1 with the input voltage detection signal Iv, and the input voltage detection signal Iv. Becomes larger than the input reference value Vr1, the first comparison signal Cp1 shown in FIG. 3B is set to the high level. The time limit circuit TI starts a time limit when the first comparison signal Cp1 becomes High level, and the first AND circuit AD1 performs an AND logic of the first comparison signal Cp1 and the time limit signal Ti, and time t = t2 At this time, the first AND signal Ad1 is set to High level and output.

  Further, the second comparison circuit CP2 shown in FIG. 2 compares the reference voltage value Vr2 set by the reference voltage setting circuit VR2 with the input voltage detection signal Iv, and when the input voltage detection signal Iv is smaller than the reference voltage value Vr2. Then, the second comparison signal Cp2 becomes low level, is made high level by the inverting circuit IN, and is inputted to the second AND circuit AND2.

  At time t = t2, the second AND circuit has the first AND signal Ad1, which is an input signal, at the High level, and the inverted signal In is also at the High level, so the second AND signal Ad2 is at the High level. When the second AND signal Ad2 becomes High level, the switching element drive circuit SD determines that the commercial AC power supply is 200V system, and repeats the first and second cycles shown in FIGS. The charging control signal Tr1 and the second charging control signal Tr2 are output. The output frequency of the first charge control signal Tr1 and the second charge control signal Tr2 is set to 6 times or more of the commercial AC power supply frequency, for example, 30 KHz of 360 Hz or more.

  At time t = t2, when the first charging control signal Tr1 shown in FIG. 3 (D) becomes a high level, the first charging switching element TR1 becomes conductive and the DC voltage rectified by the three-phase full-wave rectifier circuit. Starts charging the second smoothing capacitor C2, and charges the second smoothing capacitor C2 during the time Ta during which the first charging switching element TR1 is conducting. Subsequently, at time t = t3, when the first charging control signal Tr1 becomes the Low level, the first charging switching element TR1 is cut off, and the charging of the second smoothing capacitor C2 by the DC voltage is finished.

  Times t = t3 to t4 are rest periods td during which the first charging switching element TR1 and the second charging switching element TR2 prevent an arm short circuit.

  At time t = t4, when the second charge control signal Tr2 becomes High level, the second charging switching element TR2 is turned on, and the first smoothing capacitor C1 has the DC voltage rectified by the three-phase full-wave rectifier circuit. Charging is started and the first smoothing capacitor C1 is charged during the time Ta during which the second charging switching element TR2 is conducting. Subsequently, at time t = t5, when the second charge control signal Tr2 becomes low level, the second charging switching element TR2 is cut off, and the charging of the first smoothing capacitor C1 with the DC voltage is ended.

  During time Tb from time t = t3 to t6 shown in FIG. 3 (D), the discharge of the charging voltage of the first smoothing capacitor C2 is prevented by blocking the first charging switching element TR1.

  Subsequently, at time t = t6, the charging voltage of the first smoothing capacitor C1 and the charging voltage of the second smoothing capacitor C2 are added and rectified by a three-phase full-wave rectifier circuit as shown in FIG. The DC voltage is smoothed and doubled and supplied to the inverter circuit INV. Thereafter, the above-described charging is repeated to maintain a double voltage of the DC voltage.

  Further, the first discharge preventing diode D7 prevents the discharge of the charged electric charge of the first smoothing capacitor C1 during the time t2 to t3 when the first charging switching element TR1 is conducting, The second discharge preventing diode D8 prevents discharge of the charged electric charge of the second smoothing capacitor C2 during the time t4 to t5 when the second charging switching element TR21 is conductive. Furthermore, the first smoothing capacitor C1 and the second smoothing capacitor C2 smooth the DC voltage rectified by the three-phase full-wave rectifier circuit.

Next, the operation when the commercial AC power source is a 400V system will be described.
The second comparison circuit CP2 shown in FIG. 2 compares the reference voltage value Vr2 set by the reference voltage setting circuit VR2 with the input voltage detection signal Iv, and when the input voltage detection signal Iv is larger than the reference voltage value Vr2, The comparison signal Cp2 of No. 2 becomes High level, is made Low level by the inverting circuit IN, and is inputted to the second AND circuit AND2.

  At time t = t2 shown in FIG. 3, the second AND circuit AND2 performs AND logic between the High level of the first AND signal Ad1 and the Low level of the inverted signal In, and sets the second AND signal Ad2 to the Low level. To. When the second AND signal Ad2 becomes low level, the switching element drive circuit SD determines that the commercial AC power supply is 400V system and stops outputting the first charge control signal Tr1 and the second charge control signal Tr2. To do.

  When the charging control circuit CR stops outputting the first charging control signal Tr1 and the second charging control signal Tr2 and the first charging switching element TR1 and the second charging switching element TR2 are cut off, the three-phase The full-wave rectifier circuit three-phase full-wave rectifies a 400-V commercial AC power supply to generate a pulsating DC voltage, which is smoothed by the first smoothing capacitor C1 and the second smoothing capacitor C2 and output to the inverter circuit INV.

FIG. 3 is an electrical connection diagram of the power source device for cutting processing according to the present invention. FIG. 2 is a detailed diagram of a charge control circuit CR shown in FIG. It is a wave form diagram explaining operation | movement of the power supply apparatus for arc processing of this invention. It is an electrical connection figure of the power supply apparatus for arc processing of a prior art. It is a wave form diagram explaining operation | movement of the power supply apparatus for arc processing of a prior art.

Explanation of symbols

AD1 first AND circuit AD2 first AND circuit C1 first smoothing capacitor C2 second smoothing capacitor C3 capacitor C4 capacitor C5 capacitor C6 smoothing capacitor C7 smoothing capacitor CP1 first comparison circuit CP2 second comparison circuit D1 second 1 diode D2 2nd diode D3 3rd diode D4 4th diode D5 5th diode D6 6th diode D7 1st discharge prevention diode D8 2nd discharge prevention diode D9 diode D10 diode D11 diode D12 Diode D13 Diode D14 Diode D15 Diode D16 Diode D17 Diode D18 Diode DCL DC Reactor DR1 Secondary Rectifier Circuit ER Comparison Operation Circuit Er Comparison Operation Signal ID Output current detection circuit Id Output current detection signal IN Inversion circuit In Inversion signal IR Output current setting circuit IV Input voltage detection circuit Iv Input voltage detection signal INV Inverter circuit INT Main transformer M Workpiece SC Output control circuit SD Switching element drive circuit Sc1 first output control signal Sc2 second output control signal SW1 to 3 voltage changeover switch TH torch TI timing circuit TR1 first charging switching element Tr1 first charging control signal TR2 second charging switching element Tr2 second 2 charging control signal VR1 input reference setting circuit (input reference value)
Vr1 input reference setting circuit (input reference value)
VR2 reference voltage setting circuit Vr2 reference voltage setting signal (reference voltage value)

Claims (2)

A three-phase full-wave rectifier circuit that rectifies a commercial AC power supply and outputs a pulsating DC voltage; a first smoothing capacitor of the same capacity that is provided in parallel with the three-phase full-wave rectifier circuit and smoothes the DC voltage; A series circuit composed of two smoothing capacitors, an output control circuit for controlling the output of the inverter circuit, a main transformer for converting the high frequency AC voltage suitable for arc machining, and a DC voltage by rectifying the output of the main transformer Is provided between the plus side of the three-phase full-wave rectifier circuit and the midpoint of the series circuit, and the DC voltage is supplied to the second rectifier circuit. Provided between the first charging switching element to be supplied to the smoothing capacitor, the negative side of the three-phase full-wave rectifier circuit and the midpoint of the series circuit, and supplies the DC voltage to the first smoothing capacitor. Second charge A switching element; a first discharge preventing diode provided between a collector side of the first charging switching element and a plus side of the series circuit; and preventing discharge of the first smoothing capacitor; A second discharge prevention diode provided between the emitter side of the charge switching element of 2 and the negative side of the series circuit to prevent the discharge of the second smoothing capacitor, and the three-phase full-wave rectification An input voltage detection circuit that detects a DC voltage and outputs it as an input voltage detection signal; a predetermined input reference value; and a predetermined reference voltage value that is greater than the input reference value. the reference voltage value below the commercial AC power source when it is determined that the 200V system with the input reference value or more, the first charge control signal of the same time of the maximum conduction ratio is shifted by a half cycle from each other And a second charge control signal repeatedly output to conducting the first charge switching element and the second charge switching element, the commercial AC when the value of the input voltage detection signal is equal to or higher than the reference voltage value Charging that discriminates that the power source is a 400V system, stops the output of the first charging control signal and the second charging control signal, and shuts off the first charging switching element and the second charging switching element. A power supply device for arc machining, comprising: a control circuit; 2. The arc machining power supply device according to claim 1, wherein output frequencies of the first charge control signal and the second charge control signal of the charge control circuit are in a range of 360 Hz to 30 KHz .

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