JP2012100440A - Protective device of power supply unit for welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective device of power supply unit for welding, capable of more completely protecting a switching element constituting an inverter circuit even if failure occurs in a cooling device.SOLUTION: A control circuit, upon determination of abnormal rotation of a cooling fan, implements inverter stop control based on comparison between a fourth preset temperature d lowered from normally using third preset temperature c and a detected temperature of a temperature sensor. Thus, before a temperature of a switching element itself deviated from the detected temperature of the temperature sensor becomes excessively high, the operation of the element can be stopped.

Description

  The present invention relates to a protection device for protecting a switching element of an inverter circuit provided in a welding power supply device from overheating damage.

  A welding power source device used for an arc welding machine, etc., converts DC power obtained by rectifying AC input power from a commercial power source into high-frequency AC power by an inverter circuit, and rectifies the high-frequency AC power that is voltage-adjusted by a welding transformer. It is converted to DC output power suitable for arc welding by a DC reactor or a DC reactor.

  In such a welding power source device, for example, as in the high-frequency heating device of Patent Document 1, since the switching element constituting the inverter circuit generates heat by its own switching operation, a cooling device for cooling the element is provided. It is done. For example, the cooling device is configured to supply cooling air generated mainly by a cooling fan to a heat sink in contact with the switching element and cool the switching element through the heat sink.

  In addition, when rotation abnormality such as rotation lock or abnormal low-speed rotation occurs due to failure of the cooling fan itself or rotation prevention by foreign matter, the switching element becomes overheated due to insufficient cooling air, Since the inverter circuit is damaged, when an abnormal temperature is detected by a temperature sensor provided in the apparatus, the operation of the switching element of the inverter circuit is stopped. That is, the overheating state is further prevented, and the switching element of the inverter circuit is protected from damage.

JP 2001-110561 A

  By the way, when a temperature sensor is installed at a position separated from the plurality of switching elements, such as using one temperature sensor, there is a difference between the temperature detected by the temperature sensor and the temperature of the switching element itself. Arise.

  In particular, when the cooling fan rotates abnormally as described above and the cooling air becomes insufficient, and the detected temperature of the temperature sensor reaches the abnormal temperature and the inverter circuit is stopped, the detected temperature of the temperature sensor and the switching element itself Since the deviation from the temperature increases, it is considered that the element itself has become an excessively high temperature. That is, even if the operation of the switching element of the inverter circuit is stopped based on the detection of the abnormal temperature by the temperature sensor, there is a concern that the element has already been damaged in an excessively high temperature state.

  The present invention has been made to solve the above-described problems, and its purpose is for welding that can more reliably protect the switching elements constituting the inverter circuit even if an abnormality occurs in the cooling device. It is to provide a protection device for a power supply device.

  In order to solve the above-mentioned problems, an invention according to claim 1 is an inverter that converts input DC power into high-frequency AC power by operation of a switching element so as to generate output power for welding in a subsequent circuit. In a welding power supply apparatus including a circuit and a cooling fan that supplies cooling air to a cooling object including the switching element and cools heat generated based on the operation of the element, the temperature of the cooling object is detected. A protection device for a power supply apparatus for welding comprising a temperature sensor and an inverter stop control means for stopping the operation of the switching element of the inverter circuit based on a temperature detected by the temperature sensor, wherein the cooling fan rotation abnormality is detected. A rotation abnormality determination means for determining, wherein the inverter stop control means is determined by the rotation abnormality determination means that the cooling fan is abnormal in rotation. When lowered relatively the set temperature to be used for comparison and determination of the temperature detected by said temperature sensor, as its gist to implement the inverter stop control based on the comparison determination.

  In this invention, when it is determined by the rotation abnormality determination means that the cooling fan is abnormal in rotation, the inverter stop control means relatively lowers the set temperature used for comparison determination with the temperature detected by the temperature sensor (set temperature). Or the detected temperature side is raised to relatively lower the set temperature), and inverter stop control is performed based on the comparison determination. In other words, if the cooling fan is rotated abnormally and the cooling air becomes insufficient, the temperature of the switching element of the inverter circuit, which is the heat source, rises, and the temperature detected by the temperature sensor rises accordingly. Especially in the case where the temperature sensor is installed, the difference between the temperature detected by the temperature sensor and the temperature of the switching element itself is enlarged. Based on this, in the present invention, when the cooling fan is determined to be abnormal in rotation, the inverter stop control is performed based on a comparison between the relatively lowered set temperature and the detected temperature of the temperature sensor. Before the temperature of the switching element itself that deviates from the temperature becomes excessively high, the operation of the element is stopped, and the element is more reliably protected.

  According to a second aspect of the present invention, in the protection device for a welding power source device according to the first aspect, the rotation abnormality determining means is configured to be able to determine individual rotation abnormality of the cooling fans provided in a plurality. The gist of the invention is that the inverter stop control means is configured to vary the relative reduction width of the set temperature in accordance with the cooling fan determined to be abnormal in rotation.

  In this invention, each rotation abnormality of the cooling fans provided in a plurality of rotation abnormality determination means is determined, and the inverter stop control means reduces the set temperature relative decrease width according to the cooling fan determined to be rotation abnormality. Variable. Thereby, more suitable inverter stop control can be performed according to the situation at the time, such as the number of cooling fans determined to be abnormal rotation and the installation position.

  According to a third aspect of the present invention, in the protection device for a welding power source device according to the first or second aspect, the rotation abnormality determination means can determine rotation abnormality based on detection of a change in rotation speed of the cooling fan. The gist of the inverter stop control means is that the relative reduction width of the set temperature is variable in accordance with the degree of decrease in the rotational speed of the cooling fan.

  In this invention, the rotation abnormality determination means determines rotation abnormality based on the detection of the change in the rotation speed of the cooling fan, and the inverter stop control means determines the relative temperature of the set temperature according to the degree of decrease in the rotation speed of the cooling fan. The lowering width is variable. Thereby, more suitable inverter stop control can be performed according to the fall state of the rotational speed of the cooling fan.

  ADVANTAGE OF THE INVENTION According to this invention, even if abnormality arises in a cooling device, the protection apparatus of the power supply device for welding which can protect the switching element which comprises an inverter circuit more reliably can be provided.

It is a block diagram of the power supply apparatus for welding in this embodiment. It is an arrangement view of an inverter circuit (switching element) and a temperature sensor on a heat sink. It is operation | movement explanatory drawing of a cooling fan and an inverter circuit with respect to the temperature detected with a temperature sensor.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
As shown in FIG. 1, the welding power supply device 11 of the arc welding machine 10 converts three-phase AC input power supplied from a commercial power source into DC output power suitable for arc welding. The AC input power is converted into DC power by a rectifier circuit 12 constituted by a diode bridge or the like, and the converted DC power is converted into high frequency AC power by an inverter circuit 13.

  The high-frequency AC power generated by the inverter circuit 13 is adjusted to a predetermined voltage value by the welding transformer 14, and the voltage-adjusted secondary-side high-frequency AC power is a rectifier circuit 15 configured using a diode or the like. Is converted into DC output power suitable for arc welding. The output power generated in this way is supplied to the torch TH connected to the power supply device 11, and arc welding of the welding object M is performed.

  The inverter circuit 13 is composed of an H bridge circuit using four switching elements TR such as IGBTs, and the switching operation is performed by PWM control of the control circuit 16 of the switching element TR. The control circuit 16 controls the inverter circuit 13 so that the DC output power becomes an appropriate value from time to time.

  Further, since the switching element TR generates heat by a switching operation under PWM control, a cooling device 17 that cools the switching element TR is provided in the power supply device 11. As shown in FIGS. 1 and 2, the cooling device 17 includes a heat sink 18 to which the switching element TR is attached in a contact state, a cooling fan 19 for mainly supplying cooling air to the heat sink 18, and a predetermined heat sink 18. And a temperature sensor 20 such as a thermistor for detecting the temperature of the part and indirectly detecting the temperature of the switching element TR. The temperature sensor 20 is installed at the center position of the four switching elements TR disposed on the heat sink 18 and outputs the detected temperature to the control circuit 16 as a signal.

  The control circuit 16 recognizes the detected temperature based on the output signal from the temperature sensor 20. As shown in FIG. 3, when the detected temperature rises and exceeds a first set temperature a corresponding to the fan operating temperature, the control circuit 16 turns on the cooling fan 19 and starts the air blowing operation. Eventually, when the detected temperature decreases based on the blowing operation of the cooling fan 19 and falls below the second set temperature b corresponding to the fan stop temperature, the control circuit 16 turns off the cooling fan 19 and stops the blowing operation. Incidentally, the driving mode of the cooling fan 19 may be a mode in which the cooling fan 19 is simply turned on or off, or a mode in which rotational speed control (air flow rate control) is performed according to the detected temperature.

  The control circuit 16 also compares the third set temperature c higher than the first set temperature a that triggers the operation of the cooling fan 19 with the temperature detected by the temperature sensor 20, and the detected temperature is the first temperature. It is determined that the temperature is overheated to an abnormal temperature by exceeding the set temperature c. When the determination is made, the control circuit 16 stops the operation itself of the switching element TR of the inverter circuit 13 that is the heat generation source so that no further heat generation occurs, and protects the element TR. That is, in this case, output is stopped.

  Here, the control circuit 16 also performs rotation abnormality determination of the cooling fan 19. Incidentally, this rotation abnormality determination may be an aspect in which a deviation between the rotational speed command value and the feedback value is detected, an aspect in which the load current of the cooling fan 19 is detected, or the like. By the way, when the temperature sensor 20 is installed at a position separated from the switching element TR and the temperature of the switching element TR cannot be directly detected as in the present embodiment, the temperature detected by the temperature sensor 20 and the switching are detected. Deviation may occur in the temperature of the element TR itself. Here, when the cooling fan 19 is rotating normally, the deviation is small even when the detected temperature reaches the third set temperature c, and the control circuit 16 detects that the temperature detected by the temperature sensor 20 is the third set temperature. Even when the operation of the switching element TR of the inverter circuit 13 is stopped by exceeding c, the switching element TR itself does not reach an excessive temperature.

  On the other hand, the cooling fan 19 may have a rotation abnormality such as a rotation lock or abnormally low speed rotation due to its own failure or rotation prevention due to foreign matter. In particular, as in this embodiment, when the temperature sensor 20 is installed at a position separated from the switching element TR and the temperature of the switching element TR cannot be directly detected, the detected temperature and the switching element in the temperature sensor 20 are detected. The deviation from the temperature of TR itself increases. Therefore, if the control circuit 16 is adapted to stop the operation of the switching element TR of the inverter circuit 13 when the temperature detected by the temperature sensor 20 exceeds the third set temperature c, the switching element TR itself is already excessive. The temperature is reached (illustrated by a broken line in FIG. 3).

  Therefore, if the control circuit 16 of this embodiment determines that the rotation of the cooling fan 19 is abnormal, the control circuit 16 switches to a fourth set temperature d (temperature higher than the first set temperature a) that is sufficiently lower than the third set temperature c. The comparison with the temperature detected by the temperature sensor 20 is performed. The fourth set temperature d may be a fixed value or arbitrarily changeable. By performing such comparison and determination, the control circuit 16 stops the operation of the switching element TR of the inverter circuit 13 before the switching element TR itself becomes an excessively high temperature state. Is prevented. As a result, the switching element TR of the inverter circuit 13 is more reliably protected.

Next, characteristic effects of the present embodiment will be described.
When the cooling fan 19 becomes abnormal in rotation and the cooling air becomes insufficient, the temperature of the switching element TR of the inverter circuit 13 that is the heat source rises, and as a result, the temperature detected by the temperature sensor 20 rises. Particularly in the present embodiment in which the temperature sensor 20 is installed at the separated position, the difference between the detected temperature of the temperature sensor 20 and the temperature of the switching element TR itself is enlarged. Based on this, in the present embodiment, when the control circuit 16 determines that the cooling fan 19 rotates abnormally, the control circuit 16 compares the fourth set temperature d, which is lowered from the normally used third set temperature c, with the detected temperature of the temperature sensor 20. Based on this, inverter stop control is performed. For this reason, the operation of the element TR is stopped before the temperature of the switching element TR itself that deviates from the temperature detected by the temperature sensor 20 reaches an excessively high temperature state, and the element TR can be protected more reliably. it can.

In addition, you may change embodiment of this invention as follows.
As described above, the driving mode of the cooling fan 19 may be a mode in which the cooling fan 19 is simply turned on or off, a mode in which rotation speed control (air flow control) is performed according to the detected temperature, and the like.

  As described above, the rotation abnormality determination in the control circuit 16 is performed using a mode in which a deviation between the rotation speed command value and the feedback value is detected, a mode in which the load current of the cooling fan 19 is detected, or the like. Also good.

  In the comparison determination regarding the inverter stop control in the control circuit 16, the third set temperature c to the fourth set temperature that normally use the set temperature used for the comparison determination with the temperature detected by the temperature sensor 20 when the cooling fan 19 rotates abnormally. Although it is lowered to d, it is possible to relatively reduce the set temperature by fixing the third set temperature c and raising the detected temperature side.

  When the rotation abnormality determination in the control circuit 16 is performed based on detection of a change in the rotation speed of the cooling fan 19, the range of decrease in the set temperature when the cooling fan 19 rotates abnormally is set to the rotation speed of the cooling fan 19. It is good also as variable according to the fall degree. In this way, more suitable inverter stop control is possible depending on the situation at that time.

  -The structure of the power supply apparatus 11 for welding is an example, and you may change a structure suitably. For example, a plurality of cooling fans 19 may be provided. In this case, the rotation abnormality determination in the control circuit 16 may be performed for each cooling fan, and the number of cooling fans that are determined to be the rotation abnormality of the set temperature decrease when the cooling fan 19 rotates abnormally. It may be variable according to the installation position or the like. In this way, more suitable inverter stop control is possible depending on the situation at that time.

  -Although it implemented in the power supply apparatus 11 for welding of the arc welding machine 10, you may implement in welding power supply apparatuses other than an arc welder.

11 Welding power supply device 13 Inverter circuit 14 Welding transformer (rear circuit)
15 Rectifier circuit (rear circuit)
16 Control circuit (rotation abnormality determination means, inverter stop control means)
19 Cooling fan 20 Temperature sensor TR Switching element c, d Set temperature

Claims (3)

In order to generate output power for welding in a subsequent circuit, an inverter circuit that converts input DC power into high-frequency AC power by operation of the switching element, and cooling air is supplied to a cooling target including the switching element In a welding power supply apparatus including a cooling fan that cools heat generated based on the operation of the element, a temperature sensor that detects the temperature of the cooling target, and a temperature sensor that detects the temperature of the inverter circuit based on the detected temperature of the temperature sensor. A protection device for a welding power supply device comprising an inverter stop control means for stopping the operation of the switching element,
A rotation abnormality determining means for determining rotation abnormality of the cooling fan;
The inverter stop control means, when the rotation abnormality determination means determines that the cooling fan is abnormal in rotation, relatively lowers the set temperature used for comparison determination with the temperature detected by the temperature sensor, and compares A protection device for a welding power supply device, wherein inverter stop control is performed based on the determination. The protection device for a welding power source device according to claim 1,
The rotation abnormality determination means is configured to be able to determine individual rotation abnormality of the cooling fan provided with a plurality of units,
The protective device for a welding power supply apparatus, wherein the inverter stop control means varies a relative reduction width of the set temperature in accordance with the cooling fan determined to be abnormal in rotation. In the protective device of the power supply device for welding of Claim 1 or 2,
The rotation abnormality determination means is configured to be able to determine rotation abnormality based on detection of a change in rotation speed of the cooling fan,
The protective device for a welding power supply apparatus, wherein the inverter stop control means is configured to vary a relative decrease width of the set temperature in accordance with a degree of decrease in the rotation speed of the cooling fan.

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