CN112453647A - Inverter energy storage welding machine controller with constant current control function - Google Patents
Inverter energy storage welding machine controller with constant current control function Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/10—Other electric circuits therefor; Protective circuits; Remote controls
- B23K9/1006—Power supply
- B23K9/1043—Power supply characterised by the electric circuit
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/02—Details
- H02H3/04—Details with warning or supervision in addition to disconnection, e.g. for indicating that protective apparatus has functioned
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
- H02H3/32—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/12—Arrangements for reducing harmonics from ac input or output
- H02M1/126—Arrangements for reducing harmonics from ac input or output using passive filters
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Abstract
The invention provides an inverter energy storage welding machine controller with a constant current control function, which is characterized in that a power supply interface is connected with the input end of a rectifying circuit through an air switch with a tripping function, and a leakage current detection sensor is connected in series on a circuit between the air switch and the input end of the rectifying circuit; a current sensor is connected in series on a circuit between the output end of the inverter circuit and the welding transformer; the controller comprises a main control unit, the main control unit is connected with the leakage current detection sensor through a leakage detection circuit, and is connected with the idle switch through an idle switch tripping control circuit; the main control unit is connected with the current sensor through the current sampling circuit and controls the on or off of the IGBT device in the full-bridge inverter circuit through the trigger circuit. The invention has the leakage detection function and can detect the leakage of the AC side, the DC side and the inversion side of the whole machine.
Description
Technical Field
The invention relates to a controller of an inverter welding machine.
Background
At present, the inverter welding machine is gradually approved by virtue of the advantages of energy conservation and power saving and good welding performance, the application range of the inverter welding machine is wider and wider, the inverter welding machine is necessary to replace a common power frequency welding machine, and the market potential is very large. The principle of the inverter welding machine is that three-phase alternating current is rectified and filtered to be direct current, then the alternating current is inverted into 1KHz alternating current through an IGBT and supplied to a welding machine transformer, the alternating current is reduced in voltage through the welding transformer (the specific voltage is related to a welding process), and full-wave rectification is performed through a diode to be low-voltage direct current for welding, as shown in figure 1.
Because the domestic inverter welding machine industry starts late, is not mature in some aspects, also has a lot of practical problems, mainly has following several:
leakage protection
The requirement on welding quality in the field of automobile production is high, and the inverter welding machine is widely applied in the field. The automobile production industry mostly adopts a suspended electric welding machine and adopts a handheld integrated welding tongs for welding. The integrated welding tongs are equipment integrating a welding machine transformer, a low-voltage rectifying circuit and the welding tongs, the principle of a main circuit of the integrated welding tongs is shown in figure 2, and an operator holds the welding tongs in the hand to manually search a target welding point for welding. Because the operator directly contacts with the soldering turret, and the soldering turret is in the active state all the time, the condition such as insulation damage that probably leads to because of mechanical reason appears very much, if welding transformer or connecting cable once have the electric leakage phenomenon will directly endanger operator's safety, this needs the whole machine to have a set of reliable earth leakage protection system.
The existing inverter welding machine is usually realized by an air switch or a common leakage protector with a leakage protection function, as shown in fig. 3, the leakage detection principle of the inverter welding machine is that a three-phase power line simultaneously penetrates through a zero sequence current transformer, under the condition of no leakage, the vector sum of three-phase currents is zero, and the current induced in the zero sequence current transformer is zero. Once the leakage phenomenon occurs, the vector sum of the three-phase current is not zero, the leakage current is sensed in the zero-sequence current transformer, and the air switch is disconnected after the leakage current reaches a certain value, so that the safety is ensured.
The existing leakage protection device is generally used in conventional single/three-phase alternating current 50Hz power supply electric equipment, the voltage waveform of the 50Hz alternating current is a sine wave, and the leakage current is also a sine wave, as shown in fig. 4, the leakage current detection circuit of the existing leakage protection device is designed according to the 50Hz sine wave.
The main loop of the inverter welding machine can be divided into three parts according to different waveforms: the ac side, the dc side and the inverter side correspond to the ac side leakage condition shown in fig. 5, the dc side leakage condition shown in fig. 6 and the inverter side leakage condition shown in fig. 7.
The waveforms of the leakage currents on the direct current side and the inversion side of the inverter welding machine are not sine waves, the frequency of the leakage current is not 50Hz, the specific waveforms are shown in fig. 8 and 9, the existing leakage protection device cannot detect the leakage current, and the existing leakage protection device can only detect and protect the leakage current detected by the alternating current of the inverter welding machine. Because the alternating current side and the direct current side of the inverter welding machine are both arranged in the controller, the possibility of generating electric leakage is low, and the inverter side is the position where the electric leakage fault is most likely to occur, so the existing electric leakage detection device is almost the same as a dummy for the inverter welding machine.
At present, no leakage protection device specially used for detecting the inversion side high-frequency leakage pulse exists in China. The special leakage protection device for the inverter welding machine is available in European countries, the price is very high in China, almost reaches more than 1/3 of the total price of a controller of some low-power inverter welding machines, and cannot bear the total price at all. And the supply period is long and unstable under the influence of international environment, and sometimes the supply cannot be carried out for months or even half a year.
(II) stray inductance
The main circuit of the common inverter welding machine is generally connected by a common copper bar, the whole circuit is long from the rectifying circuit and the filter circuit to the inverter circuit, the voltage is higher, and sometimes the filter capacitor of the inverter welding machine with larger power needs to be connected in series and in parallel for use, so that the whole main circuit becomes more redundant. The longer the main loop is connected, the larger the equivalent stray inductance is, and when the IGBT is switched on and off at a high speed, high peak voltage can be generated, so that the IGBT is subjected to overvoltage breakdown and failure. The magnitude of the spike voltage is related to the magnitude of the stray inductance, and is related to the IGBT switching speed (current rising speed), and the larger the stray inductance is, the higher the spike voltage is, and the faster the IGBT switching speed is, the higher the spike voltage is.
This makes the ordinary inverter welder controller have to reduce the switching speed of IGBT to reduce the spike voltage, ensure that IGBT can normally work. However, when the switching speed of the IGBT is reduced, the switching loss of the IGBT becomes large, the amount of heat generated by the IGBT becomes large, the inverter efficiency of the entire device becomes low, and the reliability of the IGBT also decreases. The inversion frequency is 1KHz, and if the IGBT switching speed is too slow, the power of the whole machine can not be sent out.
(III) Heat sink
The cooling mode of the inverter welding machine almost adopts water cooling, the radiators are all made of aluminum according to the comprehensive consideration of cost and heat dissipation effect, the aluminum radiator is made of aluminum plates serving as heat dissipation substrates, and water paths are formed by punching holes in the aluminum plates. Because the quality of water is different in every place, the chemical property of aluminium is more active again, has certain temperature during operation again, uses to take place the oxidation scale deposit in radiator inside very easily after a period, and the cooling effect descends, and the operating temperature can be higher after the cooling effect descends, and the oxidation can be more serious, and vicious circle finally causes the water route to block up. If the IGBT cannot be processed in time, the IGBT damage fault caused by heat dissipation failure can be generated. Depending on the water quality and the environment, the problem of water path blockage may occur in at most two years in half a year.
(IV) Filter capacitor
The filter circuit of the existing inverter welding machine generally adopts an electrolytic capacitor, and the electrolytic capacitor has the characteristics of large capacity and low cost. The voltage after three-phase rectification is DC530V, the highest withstand voltage of the conventional electrolytic capacitor is 450V, and the highest withstand voltage of the electrolytic capacitor is only 550V. The rated voltage of the capacitor is generally selected according to 1.5 times of the actual voltage, and the capacitor with the rated voltage more than or equal to 800V is required. The electrolytic capacitors can only be used in series, the structure is complex due to the series use, and the problem of voltage sharing can also exist in the series use. The electrolytic capacitor has a certain leakage current which is determined by the characteristics of the electrolytic capacitor, and the magnitude of the leakage current can reach mA (milliampere). As shown in fig. 10, the leakage current corresponds to two resistors R1/R2 connected in series to the DC power supply, the resistors R1/R2 divide the voltage of the DC530V, and when R1 is equal to R2, the voltages of the resistors are equal. Since the leakage current of each electrolytic capacitor is different, the equivalent resistance is also different from R1 ≠ R2, and the voltage division on the resistance is also different. If the difference between the leakage currents of two electrolytic capacitors connected in series is large, the actual voltage at two ends of the capacitor with small leakage current is larger than the rated value, and the voltage breakdown of the capacitor is caused.
The electrolytic capacitor has larger leakage current, larger internal resistance and poor high-frequency response, and in practical use, the electrolytic capacitor generates heat seriously, partial electrolyte is gradually dried due to the heat generation, the capacitance is reduced, the internal resistance is larger after the capacitance is reduced, the heat generation is more serious, and the capacitor finally fails due to vicious circulation.
The rated service life of the common electrolytic capacitor is 2000 hours, the long service life is 5000 hours, and the ultra-long service life is 10000 hours. Even if the long-life type is used for two years at most, it is not heated, as calculated by operating for 8 hours per day. It is a practical matter that even an ultra-long life electrolytic capacitor has a service life of only two years at most because the rated service life is greatly shortened by the influence of heat generation in use. After the electrolytic capacitor is used for a certain service life, the temperature is higher and higher, the electrolytic capacitor is very likely to burst (an explosion-proof valve is generally arranged and is opened when the temperature is too high), the explosion-proof valve is opened, the electrolyte remained in the capacitor is sprayed out at the moment, the electrolyte is sprayed to devices such as a main control board, an IGBT and the like, and the electrolytic capacitor is conductive and corrosive and difficult to clean, so that the inverter welding power supply which is burst by the capacitor is almost scrapped, has no maintenance value and causes great loss to companies and users.
The electrolytic capacitor has positive and negative polarities, and the polarity needs to be noticed during installation, so that the electrolytic capacitor can be exploded once reversely installed.
The use of electrolytic capacitors is generally more disadvantageous.
Disclosure of Invention
The invention aims to solve the technical problems that the existing inverter welding machine does not have a reliable leakage protection system, has larger equivalent stray inductance and is unreliable in heat dissipation.
In order to solve the technical problems, the technical scheme of the invention is to provide an inverter energy storage welding machine controller with a constant current control function, the main loop of the inverter energy storage welding machine comprises a rectifying circuit, the input end of the rectifying circuit is connected with a power interface, the output end of the rectifying circuit is connected with the input end of an inverter circuit through a filter circuit, the output end of the inverter circuit is connected with a welding transformer, wherein, the inverter circuit adopts a full-bridge inverter circuit, one bridge arm of the full-bridge inverter circuit consists of an IGBT device VT1 and an IGBT device VT4, the other bridge arm consists of an IGBT device VT2 and an IGBT device VT3, two bridge arms of the full-bridge inverter circuit are conducted in turn by taking T as a cycle, the power supply interface is connected with the input end of the rectifying circuit through an air switch with a tripping function, and a leakage current detection sensor is connected in series on a circuit between the air switch and the input end of the rectifying circuit; a current sensor is connected in series on a circuit between the output end of the inverter circuit and the welding transformer;
the controller comprises a main control unit, the main control unit is connected with the leakage current detection sensor through a leakage detection circuit, and is connected with the idle switch through an idle switch tripping control circuit; the main control unit obtains a leakage current value by sampling through a leakage current detection circuit and a leakage current detection sensor, compares the leakage current value with a set value, and controls an idle switch release through an idle switch release control circuit if the leakage current value exceeds the set value so as to cut off a three-phase input power supply input through a power interface;
the main control unit is connected with the current sensor through a current sampling circuit and controls the on or off of an IGBT device in the full-bridge inverter circuit through a trigger circuit; the main control unit acquires a current signal output by the inverter circuit through the current sampling circuit by using the current sensor, and controls the on or off of an IGBT device in the full-bridge inverter circuit through the trigger circuit according to the acquired current signal so as to realize constant current control; when constant current control is carried out, a user sets a current set value and welding time of required welding current through a man-machine interaction unit connected with a main control unit, the main control unit compares an actual current value corresponding to a current signal obtained through a current sampling circuit with the current set value, and if the actual current value is smaller than the current set value, the main control unit increases the duty ratio of an IGBT device in an inverter circuit through a trigger circuit to increase the actual current value; if the actual current value is larger than the current set value, the main control unit reduces the duty ratio of the IGBT device through the trigger circuit, so that the actual current value is reduced;
the main control unit is connected with a protection circuit, the protection circuit is simultaneously connected with the current sensor, the protection circuit judges whether the actual current value is overlarge by adopting a hardware comparison mode, and when the actual current value of the current signal output by the inverter circuit exceeds a specified value, the protection circuit gives an alarm; the control unit judges whether the protection circuit generates an alarm or not through the interrupt signal, when the protection circuit generates the alarm, the control unit detects the interrupt signal, determines that an overcurrent phenomenon occurs, immediately stops working, and sends alarm information to the human-computer interaction unit for displaying;
the main control unit also detects the direct current voltage rectified by the rectifying circuit through a voltage sampling circuit and displays the direct current voltage through the human-computer interaction unit.
Preferably, the leakage current detection circuit converts a leakage current signal detected by the leakage current sensor into an ac pulse voltage signal, and then converts the ac pulse voltage signal into a dc pulse voltage signal, and the leakage current detection circuit sends the dc pulse voltage signal to the main control unit.
Preferably, the air switch is provided with a release, and the air switch is released immediately after the release is connected with the power supply of the DC 24V.
Preferably, the leakage current detection circuit comprises an operational amplifier IC1-1, a non-inverting input terminal of the operational amplifier IC1-1 is connected with a resistor R19 and a resistor R20 which are connected in series, the resistor R20 is grounded, and the leakage current sensor is connected in parallel to the resistor R20; the inverting input terminal of the operational amplifier IC1-1 is grounded through a resistor R18; a diode Z13 and a diode Z12 which are connected in parallel are connected between the non-inverting input end and the inverting input end of the operational amplifier IC 1-1; the anode of the diode Z13 is connected with the non-inverting input end of the operational amplifier IC1-1, and the cathode of the diode Z13 is connected with the inverting input end of the operational amplifier IC 1-1; the cathode of the diode Z12 is connected with the non-inverting input end of the operational amplifier IC1-1, and the anode of the diode Z12 is connected with the inverting input end of the operational amplifier IC 1-1; the output end of the operational amplifier IC1-1 is connected with the inverting input end of the operational amplifier IC2-1 through a resistor R16; a resistor R17 is connected between the output end and the inverting input end of the operational amplifier IC1-1 in a bridging way;
the non-inverting input end of the operational amplifier IC2-1 is grounded; the diode Z10 is connected in series with the resistor R13 and then connected in parallel with the diode Z11 and the resistor R12 which are connected in series to form a parallel circuit, the parallel circuit is bridged between the output end and the inverting input end of the operational amplifier IC2-1, the anode of the diode Z10 and the cathode of the diode Z11 are connected with the output end of the operational amplifier IC2-1, the cathode of the diode Z10 is connected with the resistor R13, and the anode of the diode Z11 is connected with the resistor R12;
the non-inverting input end of the operational amplifier IC2-2 is connected with the cathode of the diode Z10; the inverting input end of the operational amplifier IC2-2 is connected with the anode of a diode Z11 through a resistor R14; the output end of the operational amplifier IC2-2 is connected with the A/D conversion input end of the main control unit; a resistor R11 is connected across the output terminal and the inverting input terminal of the operational amplifier IC 2-2.
Preferably, the idle trip control circuit comprises a transistor Q2 and an optocoupler IC1, wherein:
the emitter of the transistor Q2 is connected with a constant voltage source; the base electrode of the transistor Q2 is connected with the control signal output end of the main control unit through a resistor R1; the collector of the transistor Q2 is grounded via a resistor R2 and a light emitting diode Z1 which are connected in series, and the collector of the transistor Q2 is connected with the primary side of the optocoupler IC1 via a resistor R3;
the secondary side of the optocoupler IC1 is bridged between the base and the collector of the transistor Q1, the emitter of the transistor Q1 is grounded, the collector of the transistor Q1 is connected with the relay J1, and the relay J1 is connected with a diode Z2 in parallel; after the relay J1 is electrified and sucked, a normally open contact J1-1 of the relay J1 is switched on, and a release is switched on a DC24V power supply, so that the idle switch is released; after the relay J1 loses power, the normally open contact J1-1 of the relay J1 is opened, and the tripper is disconnected with the DC24V power supply.
Preferably, after welding is started, when the main control unit performs constant current control, the following steps are adopted to obtain the turn-on time of the IGBT device in the inverter circuit of each period T so as to adjust the duty ratio:
step 2, calculating the root mean square value of the sampled N-point current to obtain an effective value Irms of the welding current, wherein the calculation formula is as follows:
in the formula InRepresenting the current value obtained by the nth sampling;
step 3, the main control unit predicts the required turn-on time of the corresponding IGBT device when the actual current value is equal to the current set value according to the effective value Irms obtained by calculation, and the required turn-on time is used as the turn-on time of the IGBT in the next period;
and 4, continuously sampling the output current of the inverter circuit for N times in the next period, correcting the rising rate of the current obtained by calculation in the previous period, and returning to the step 2 until the welding time is reached.
Preferably, the filter circuit employs a thin film capacitor.
Preferably, the rectifying circuit, the filter circuit and the inverter circuit are connected into a whole through a laminated busbar, and the loop is shortest.
Preferably, the rectifying circuit and the inverter circuit are jointly installed on a radiator, wherein the radiator comprises an aluminum plate, an O-shaped groove is formed in the back of the aluminum plate by adopting a CNC (computerized numerical control) process, the O-shaped groove is in a U shape on the aluminum plate, a copper tube is embedded into the O-shaped groove and then filled in a gap by adopting heat-conducting glue containing metal powder, finally, the surface is ground flat by a grinding machine, and the copper tube is connected with a water way connector outside the controller of the inverter energy storage welding machine; the rectifier circuit and the inverter circuit are fixed on the front face of the aluminum plate, heat conducting grease is coated on the contact surface of the high-power semiconductor device in the rectifier circuit and the inverter circuit and the aluminum plate, the high-power semiconductor device is fully contacted with the radiator, cooling water flows through the copper tube, and heat in the aluminum plate is taken away through the copper tube.
Preferably, the control unit is connected with a memory, 32 welding specifications are preset in the memory, and different welding specifications can be set for different welding points through the human-computer interaction unit;
the control unit is also connected with the signal output interface through the action output unit and is connected with the signal input interface through the action input unit.
Compared with the prior art, the invention has the following advantages:
1) the leakage detection function is provided, and the leakage of the alternating current side, the direct current side and the inversion side of the whole machine can be detected;
2) the laminated busbar technology is adopted to replace the connection of the common copper bars of the main loop, so that the stray inductance of the main loop is reduced;
3) the radiator manufactured by a brand new process is adopted, so that cooling water is not contacted with aluminum any more, the oxidation of the aluminum is avoided, and the possibility of water channel blockage is reduced;
4) the dry-type film capacitor with smaller leakage current and longer service life is adopted without using an electrolytic capacitor, so that the reliability of the whole machine is greatly improved.
Drawings
FIG. 1 is a schematic circuit diagram of an inverter welder;
FIG. 2 is a schematic diagram of a main circuit of the hand-held integrated soldering turret;
FIG. 3 is a schematic diagram of a current leakage device used in a conventional inverter welding machine;
FIG. 4 is a schematic diagram of a 50Hz leakage waveform;
FIG. 5 is an AC leakage condition of the main circuit of the inverter welder;
FIG. 6 is a DC side leakage of the main circuit of the inverter welder;
FIG. 7 is a reverse side leakage of the main circuit of the reverse welding machine;
FIG. 8 is a DC side leakage current waveform for an inverter welder;
FIG. 9 is a waveform of the inverter side leakage current of the inverter welder;
FIG. 10 is a leakage current equivalent circuit of an electrolytic capacitor;
FIG. 11 is a block diagram of the system of the present invention;
FIG. 12 is a schematic circuit diagram of a full bridge inverter circuit;
FIG. 13 is a schematic diagram of the current direction of the full-bridge inverter circuit at time T1;
FIG. 14 is a schematic diagram of the current direction of the full-bridge inverter circuit at time T2;
FIG. 15 is a load current, voltage waveform;
FIGS. 16 and 17 illustrate a method for adjusting current in an inverter welder;
FIG. 18 is a block diagram of a circuit for implementing the leakage detection function of the present invention;
FIG. 19 is a schematic view of an air switch installation position;
FIG. 20 is a schematic diagram of a leakage detection circuit;
FIG. 21 is a flowchart of the operation of leakage detection;
FIG. 22 is a view showing a structure of a laminated busbar;
FIG. 23 is a schematic view of a heat sink;
FIG. 24 is an equivalent circuit diagram of the inverter circuit and the welding transformer;
fig. 25 is IGBT on/off time;
FIG. 26 shows a short circuit of the IGBT legs;
fig. 27 is the dead time of the IGBT;
FIG. 28 is a constant current control waveform;
fig. 29 is a partially enlarged schematic view of a portion a of fig. 28;
FIG. 30 is a single point multiple specification diagram;
FIG. 31 is a schematic illustration of three welding currents at different times that can be set for a weld;
FIG. 32 is a schematic view of a welding current pulse cycle;
FIG. 33 is a current ramp up/ramp down waveform;
FIG. 34 is a continuous welding waveform;
FIG. 35 is a timing diagram of power distribution;
FIG. 36 is a waveform diagram of input/output operation;
fig. 37 is a program flow chart of the present invention.
Detailed Description
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.
As shown in fig. 11, the inverter energy storage welding machine controller with the constant current control function provided by the invention mainly comprises a CPU, a memory, a communication circuit, a touch screen, an action input unit, an action output unit, a trigger circuit, a current sampling circuit, a protection circuit, a voltage sampling circuit, a leakage detection circuit, an open/close control circuit, a power supply and the like. The main loop of the inverter energy storage welding machine comprises an air switch with a tripping function, a leakage detection sensor, a rectification circuit, a filter circuit, an inverter circuit, an integrated electrode holder circuit and the like. The following description is made for each part:
one) CPU and memory
In this embodiment, the CPU uses SH99F100, which is a dual-core (enhanced 16-bit DSP and 8-bit MCU) chip. The MCU can be used to handle switching values, inputs and outputs, and communications, while the DSP only needs to focus on the operations of the control algorithm. The architecture of a DSP consists of three parallel computing units (ALU, MAC, shift), two independent address generators (DAG) and one powerful Program Sequencer (PSQ). The computational unit provides computational functions that all processors are capable of providing, including single cycle multiply/accumulate, bit manipulation, shift manipulation, and the like. The dual Data address generator architecture enables the CPU to fetch two Data areas (Data Memory and Program Memory) simultaneously in one cycle. The program sequencer implements single cycle operation of all instructions, fast interrupt response, and nested, non-CPU-intervening cycles. A16-bit PWM module, a Quadrature Encoding Interface (QEI) and a 14-bit pipelined ADC and an operational amplifier (OP) are used as internal and external peripherals of the DSP core, and various industrial control algorithms can be conveniently realized. The MCU core is a high-speed high-efficiency 8051 compatible core, and has the characteristics of faster operation and more excellent performance compared with the traditional 8051 chip under the same oscillation frequency, and the resources of the MCU core are as follows: 256 bytes of SRAM, external 3840 bytes of SRAM, 3 16-bit timers and 3 external interrupts are built in, and 2 enhanced UARTs and 1 SPI interface are integrated.
In this embodiment, the memory uses X5325, which integrates four functions: the system comprises a power-on reset control device, a watchdog timer, a voltage reduction management device and a serial EEPROM with a block protection function. The method is beneficial to simplifying the design of an application system, reducing the occupied area of the printed board and improving the reliability. The serial EEPROM in the memory chip is a block-locked protection CMOS serial EEPROM with Xicor company, which is organized into an 8-bit structure, is operated in an SPI bus mode consisting of four wires, the erasing period is at least one million times, and the written data can be stored for 100 years.
II) communication circuit and touch screen
The invention adopts the touch screen as a human-computer interaction interface, and the touch screen and the CPU exchange data in a communication mode. The serial port of the touch screen is RS485, and the communication circuit converts the serial port of the CPU into an RS485 level interface to be connected with the touch screen. In order to improve the anti-interference capability, the communication circuit is completed by adopting an isolation communication chip ADM 2483.
The touch screen adopts TK6071 series, the screen size is 7 inches, and the resolution is 800 × 480. The touch screen display picture is designed and manufactured through configuration software easy builder Pro and is divided into a plurality of different pages according to functions, and the different pages mainly comprise a main picture, a standard setting picture, a parameter setting picture and the like.
The communication protocol between the touch screen and the CPU is Modbus RTU, the touch screen is used as a host to actively initiate communication, the CPU is used as a slave, and the data format is 1-bit start bit, 8-bit data bit, 1-bit check bit (even check), 1-bit stop bit and baud rate 9600. The instruction format is as follows:
read instruction format:
the upper computer sends an instruction
Address (single byte) + function code (single byte) + start address (2 bytes, H + L) + number of read words (2 bytes, L + H) + check code CRC16
Lower computer return instruction
Address (one byte) + function code (one byte) + number of bytes read (2 bytes, H + L) + data read (2 bytes, H + L) + check code CRC16(2 bytes, H + L)
Write instruction format:
the upper computer sends an instruction
Address (one byte) + function code (one byte) + start address (2 bytes, H + L) + data to be written (2 bytes, H + L) + check code CRC16(2 bytes, H + L)
Lower computer return instruction
Address (one byte) + function code (one byte) + start address (2 bytes, H + L) + written data (2 bytes, H + L) + check code CRC16(2 bytes, H + L)
Third) action input unit and action output unit
The CPU mainly receives signals for starting welding, alarming reset, specification selection and the like through the action input unit. The CPU mainly outputs the actions of a gas valve control signal, a welding end signal, an alarm signal and the like through the action output unit. The operation input unit and the operation output unit both use a DC24V power supply.
Four) trigger circuit
The trigger circuit controls the on and off of the IGBT of the inverter circuit in the main loop of the inverter energy storage welding machine according to the instruction of the CPU, the working state of the IGBT can be detected, once the abnormal working of the IGBT is found, the CPU is immediately informed, the CPU immediately stops working, and the alarm information is sent to the touch screen to be displayed.
In this embodiment, the trigger circuit is implemented by using a 2QD0108T17 driving core, the driving core is powered by DC15V, and 1W driving power can be output in one way.
Five) current sampling circuit, protection circuit, voltage sampling circuit
The current sampling circuit processes an inverter output current signal sampled by a current sensor connected in series at the output end of an inverter circuit in a main loop of the inverter energy storage welding machine. The current sampling circuit firstly changes alternating current signals into direct current signals, performs hardware filtering processing, then sends the direct current signals to a CPU for A/D conversion sampling, and sends the direct current signals to a touch screen for display after calculation.
The inverter output current signal sampled by the current sensor also enters a protection circuit, and the protection circuit is used for alarming when the load current exceeds a specified value and prompting a user that the load current is too large. In this embodiment, the protection circuit determines whether the current is too large by hardware comparison, and the CPU determines the current by an interrupt signal. After the CPU detects the interrupt signal, the CPU considers that an overcurrent phenomenon occurs, immediately stops working, and sends alarm information to the touch screen for displaying.
The voltage sampling circuit is used for detecting the three-phase rectified direct-current voltage in the main loop of the inverter energy storage welding machine. In this embodiment, the voltage sampling circuit performs dc voltage sampling by using an optical coupling isolation and resistance current limiting method, amplifies and processes a voltage signal by using an operational amplifier, and then sends the amplified voltage signal to an a/D sampling port of a CPU, and sends the amplified voltage signal to a touch screen for display after calculation.
Sixth) leakage detection circuit and air-break tripping control circuit
The leakage detection circuit processes a leakage current signal detected by the leakage current sensor, converts the leakage current signal into an alternating current pulse voltage signal, converts the alternating current pulse voltage signal into a direct current pulse voltage signal, finally enters an A/D sampling port of the CPU, and displays a real-time leakage current value through the touch screen after the calculation of the CPU.
The CPU compares the sampled leakage current value with a set value, and once the actual leakage current value exceeds the set value, the DC24V power is sent to the air switch with the tripping function through the air switch tripping control circuit, and the air switch is immediately tripped to cut off the three-phase input power.
Seven) power supply
The power needed by the control loop is provided by the switch power supply after the AC380V is stepped down by the transformer. The touch screen power supply is directly provided after voltage reduction and rectification by a transformer.
Eight) air switch with tripping function
The air switch is used as a switch of the power supply of the whole machine and is provided with a DC24V tripper, and the air switch can be immediately tripped after the tripper is connected with the DC24V power supply.
Nine) rectifier circuit
A rectification circuit of a main loop of the inverter energy storage welding machine is a three-phase bridge type rectification circuit, three-phase alternating current is converted into pulsating direct current, and the withstand voltage grade of a rectification device is 1600V.
Ten) filter circuit
The filter circuit of the main loop of the inverter energy storage welding machine generally adopts a capacitor for filtering, and the capacitor bears the ripple current of a power supply and also bears the reactive current of a load. The controller adopts the film capacitor for filtering, and has higher current bearing capacity and better high-frequency response than an electrolytic capacitor.
Eleven) inverter circuit
The inverter circuit of the main loop of the inverter energy storage welding machine adopts full-bridge inversion, as shown in fig. 12, the full-bridge inverter circuit in the embodiment adopts four IGBTs, and the four IGBTs are turned on in pairs in turns. As shown in FIG. 13, VT1 and VT4 are turned on at the same time at T1, and a forward voltage is generated across RL. As shown in FIG. 14, VT2 and VT3 are turned on at the same time at T2, and a reverse voltage is generated across RL. VT1 and VT4 are turned on again at time T3, and so on, and an alternating current IR of a certain frequency is generated in the load RL, as shown in fig. 15. The inverter welder controller generally adjusts the output current in a PWM manner, and changes the magnitude of the inverter output current by adjusting the duty ratio of the PWM, so as to change the magnitude of the welding current, as shown in fig. 16 and 17.
The inverter energy storage welding machine controller with the constant current control function realizes the electric leakage detection function by adopting the following technical scheme:
and sampling the leakage current by adopting an A/D conversion mode, and calculating and comparing the leakage current signal by using a CPU (central processing unit). The invention has no requirement on the frequency and the waveform of the leakage current, so the leakage current on the alternating current side can be detected, and the leakage current on the direct current side and the inversion side can also be detected.
As shown in fig. 18, the circuit for implementing the leakage detection function in the present invention mainly includes a leakage current detection sensor T, a leakage detection circuit, a CPU, a trip control circuit, and a dead-start with a trip function.
The air switch is installed at the input end of the whole machine three-phase power supply, the release is installed inside the air switch, and the leakage detection sensor T is installed at the output end of the air switch, as shown in fig. 19. The leakage detection circuit and the tripping control circuit are positioned on the mainboard.
As shown in fig. 20, the leakage current detection sensor T sends the detected leakage current signal to the leakage current detection circuit of the motherboard, the leakage current signal is amplified by the operational amplifier IC1-1, then the ac pulse signal is converted into the dc pulse signal by the operational amplifier IC2-1 and the operational amplifier IC2-2, and the dc pulse signal is sent to the a/D conversion input terminal of the CPU by the resistor R10. The CPU calculates and processes the leakage current signal, compares the leakage current signal with a set value, and if the actual leakage current exceeds the set value, the CPU enables the transistor Q2 to be conducted through the resistor R1, the primary side of the optical coupler IC1 has current to pass through, and the secondary side of the optical coupler IC1 is conducted, so that the transistor Q1 is conducted. After the transistor Q1 is conducted, the relay J1 is electrified and attracted, the normally open contact J1-1 is conducted, and the tripper is conducted with the DC24V power supply, so that the idle switch is tripped. The specific work flow is shown in detail in fig. 21.
When the system works normally, the CPU sends the collected leakage current value to the touch screen for display, so that a user can know the insulation condition of the current system in real time.
The controller solves the problem of stray inductance of a main loop of a common inverter welding machine controller. The sampling laminated busbar technology of the invention connects the rectifying circuit, the filter circuit and the inverter circuit into a whole, and the loop is shortest, so that the stray inductance of the main loop is reduced to the minimum, and the high-speed switching of the IGBT is ensured.
As shown in fig. 22, when the laminated busbar is manufactured, the copper plate is punched and punched as required to form the positive copper plate electrode 1 and the negative copper plate electrode 2. Then an interlayer insulating film 3 is coated between the positive copper plate electrode 1 and the negative copper plate electrode 2 and then pressed together, and finally the outside is sealed by an outer layer insulating film 4.
After the invention uses the laminated busbar technology to connect the rectifying circuit, the filter circuit and the inverter circuit, stray inductance is greatly reduced, and the invention has high reliability and safety; the structure of the whole machine is simple and compact; the impedance is lower; fool-proof installation can be realized, and errors can be avoided.
The invention also improves the water-cooling radiator, the rectification circuit and the inverter circuit are arranged on one radiator, the water path joint is arranged outside the casing of the controller, and the hidden trouble of water leakage does not exist in the controller. The radiator adopts the mode of inlaying the copper pipe as the water pipe, so that the cooling water is not contacted with the aluminum any more, the problem that the aluminum is easy to oxidize and scale is avoided, and the working reliability of the whole machine is greatly improved.
As shown in fig. 23, the base body of the heat sink is an aluminum plate 5, an O-shaped groove 6 is formed in the aluminum plate by a CNC process, and the O-shaped groove 6 is U-shaped on the aluminum plate 5 as a whole. And then, the copper tube is embedded into an O-shaped groove 6 through a large-tonnage press, then, a heat-conducting glue containing metal powder is adopted to fill the gap, and finally, the surface of the radiator is ground to be flat through a grinding machine. When the high-power semiconductor device is installed, the contact surface between the high-power semiconductor device and the radiator in the rectification circuit and the inverter circuit is coated with heat-conducting grease, so that the high-power semiconductor device and the radiator are fully contacted. The cooling water flows through the copper tube, and the heat in the aluminum plate is taken away through the copper tube.
The whole machine of the invention has compact and simple structure. The chemical property of copper is stable, and the copper is not easy to react with impurities in water, so that the problem of scaling is avoided, and the possibility of blockage is reduced. The heat radiation performance of the heat sink does not substantially change. The integrated design reduces the possibility of water leakage and provides guarantee for the reliable work of the whole machine.
The filter circuit adopts a novel film capacitor, has much smaller heat productivity than a common electrolytic capacitor, and has longer service life.
The thin film capacitor is a dry capacitor, and is made by forming a layer of thin metal as a conductive electrode on a base film by adopting a vacuum distillation technology, winding the thin metal into a cylinder shape, and then filling the cylinder shape into an aluminum shell. The thin film capacitor does not use aluminum foil as an electrode as in the electrolytic capacitor.
The thin film capacitor does not need to distinguish polarities, and is convenient to install. The thin film capacitor has high insulation resistance, small leakage current and low heat productivity. The film capacitor has good high-frequency response, small dielectric loss and large ripple current. The thin film capacitor has long service life which is more than 10 times of that of the common electrolytic capacitor. The thin film capacitor has high voltage resistance, can easily achieve rated voltage of more than 800V, does not need to be connected in series for use, and has a simple structure.
The thin film capacitor also has certain self-healing property. The self-healing property means that when the local two-layer electrodes of the capacitor are punctured, the metal powder around the short-circuit part is evaporated by heat brought by short-circuit current, and insulation is recovered. Theoretically, the thin film capacitor does not have the problem of short circuit failure.
The inverter energy storage welding machine controller with the constant current control function can realize the following functions:
1. constant current control function
(1) The control mode is as follows:
the constant current control is divided into a primary constant current and a secondary constant current, the control principle is the same, and only the sampling mode is different. The primary constant current sampling and setting is the primary current of a welding transformer in a main loop of the inverter welding machine controller, and the secondary constant current sampling and setting is the secondary current of the welding transformer. And the welding current output by the welding transformer is controlled by changing the conduction time (duty ratio) of the IGBT device in the inverter loop.
(2) The control principle is as follows:
a user sets required welding current and welding time through a touch screen, the required welding current is a set value, a CPU detects that the current value is an actual current value through a current sampling circuit, the CPU compares the actual current value with the set value, and if the actual current value is smaller than the set value, the CPU sends an instruction to increase the duty ratio of an IGBT device in an inverter circuit so as to increase the actual current value; if the actual current value is larger than the set value, the CPU sends an instruction to reduce the duty ratio of the IGBT device, so that the actual current value is reduced.
(3) Circuit characteristics:
the load of the inverter welding power supply is a welding transformer, which is equivalently a series circuit of a resistor R and an inductor L, and as shown in fig. 24, a certain phase difference exists between the current and the voltage on the resistor R.
The inverter circuit in the main loop of the inverter welding machine adopts full-bridge inversion, two bridge arms of VT1, VT4, VT2 and VT3 are alternately conducted, when VT1 and VT4 are turned on, VT2 and VT3 are turned off, and when VT2 and VT3 are turned on, VT1 and VT4 are turned off, theoretically, the possibility that VT1 and VT3 or VT2 and VT4 are simultaneously turned on cannot exist. However, due to the hysteresis of the actual driving circuit and the influence of the miller capacitance of the IGBT, the IGBT needs certain time Ton and Toff when being turned on/off, where Ton is the time needed by the IGBT when being turned on, and Toff is the time needed by the IGBT when being turned off, so that there is a possibility that short-time VT1 and VT3 or VT2 and VT4 may be turned on simultaneously during actual operation, which may cause a short-circuit of the power supply. Therefore, when the two bridge arms are switched, VT1 and VT4 are guaranteed to be closed, and VT2 and VT3 can be opened after a time delay, so that the inverter circuit is guaranteed to work normally. Similarly, after the VT2 and VT3 are turned off, a time delay is needed to turn on the VT1 and VT4, and the time delay is called dead time. In the dead time 4, only the IGBT is in an off state, and the follow current in the equivalent inductor L forms a loop through the diode VD and the capacitor C. The dead time cannot be set to be too large, the turn-on time of the IGBT in the whole period can be reduced if the dead time is too large, the maximum output power of the whole system is influenced, and the dead time is generally 2-4us after the IGBT is completely turned off under the frequency of 1KHz, so that the condition that the inverter loop is not short-circuited can be ensured. The dead time is generally set only by considering the switching time Ton and Toff of the IGBT, and the switching time of the IGBT is related to the driving voltage, the driving resistance and the parameters thereof and is unrelated to the load change.
The resistance welding has the characteristics of large current and short time, so that a welded workpiece cannot deform and change color, the welding efficiency is high, the welding current is required to be increased quickly, the control precision is required to be high, and the consistency of each welding is required to be good. The existing constant current control method generally adopts PID control, the rising speed of current is slow, the whole welding time becomes very long, workpieces are easy to deform and discolor, and the working efficiency is very low. It is desirable to ramp up the welding current to the desired value at the fastest rate and stabilize it near the set point.
(4) The control method comprises the following steps:
the 1KHz cycle time T is 1ms, after welding is started, the IGBT is turned on for 20% of a half cycle T/2 in the first cycle, about 100us (the dead time is ignored), the output current is continuously sampled N times, and the current rising rate, that is, the current rising slope in fig. 28 and 29, is calculated by comparing the current sampled current with the previous sampled current. Besides the calculation of the current rise rate, the root mean square value calculation is also carried out on the sampled N-point current to obtain the effective value Irms of the welding current, and the calculation formula is as follows:
in the formula InThe current value obtained by the nth sampling is shown.
And predicting the IGBT turn-on time required when the actual current value is equal to the set value according to the calculation result, taking the IGBT turn-on time as the IGBT turn-on time of the second period, calculating the current sampled in the second period, correcting the current rise rate calculated in the first period, simultaneously comparing the actual current value with the set value again to obtain the IGBT turn-on time of the third period, calculating, comparing and predicting, and sequentially carrying out the fourth period and the fifth period until the current welding is finished.
2. Multiple welding specification storage and invocation
The user can preset a maximum of 32 welding specifications to be stored in the memory so as to adapt to different welding process requirements. Each specification has 17 parameters, which are: prepressing time, pressurizing time, preheating current, preheating time, interval, slow rising, welding current, welding time, interval, slow falling, tempering current, tempering time, maintaining time, resting time, pressurizing delay and pressurizing time. The user can select the calling standard through 5 binary codes, can constitute automated control system with industrial control equipment such as PLC, select the welding standard through equipment such as PLC.
Normalized parameter table
Normalized call table
In the table, "1" represents on and "0" represents off
3. Single point multiple specification
When a workpiece needs to be welded with a plurality of welding points, because of the problems of shunt and different positions of the welding points, the welding current needed by each welding point may be different, and if the method of manually changing the welding current for each welding point is adopted, the method is very complicated and the efficiency is very low. The problem can be effectively solved by using a single-point multi-specification function. Different welding currents and welding time are preset according to different welding points through different specifications in advance, different welding points are welded according to a certain sequence, and different welding specifications are automatically switched to be welded through a program.
For example, as shown in fig. 30, a workpiece has 5 welding spots to be welded, each welding spot requires different currents, wherein the current required by the welding spot number 1 is the minimum, the currents are sequentially increased, the total specification number is set to 5, the specifications 1 to 5 are respectively set to the required welding currents, after welding is started, the welding spots are automatically welded for 1 to 5 points, the welding spot number 1 uses the specification number 1, the welding spot number 2 uses the specification number 2, and so on, after welding of the welding spot number 5 is completed, the welding is stopped, and welding is waited to be started again.
4. Multiple welding pulses
Three sections of welding currents of different time periods can be set in one welding, namely preheating current, welding current and tempering current, wherein the welding current and the interval can be circulated, and the circulation frequency can be set to be 99 times at most.
5. Current slow rising/slow falling
The surface of some workpieces may have certain greasy dirt or processing burrs, the phenomenon of poor contact exists, and if welding is carried out by directly using welding current and the condition of splashing is easy to occur, the splashing can cause the reduction of welding quality. The burr or oil stain is required to be burnt off by using a small current, the workpiece is in good contact with the electrode and then is welded by using a large current, and the phenomenon of welding splashing can be effectively prevented by using the current slow-rising function.
Some workpieces do not allow the welding current to be suddenly interrupted after welding is finished, otherwise, welding spots can crack and the like, and the current slow-falling function can enable the welding current to fall at a constant speed so as to meet the requirements of a welding process.
The time for the current to ramp up/down can be set according to the requirement, and is generally from several cycles to over ten cycles.
6. Counting function
The number of welding points is counted and can be displayed through selection of a counter/conventional key, a user can conveniently know the production capacity through the function, and counting is not performed in an adjusting state.
7. Working/setting state
Two working states are set, namely 'working' and 'setting'. The 'working' state means that the controller is ready to finish, can receive a welding starting command at any time for welding, and the parameter can not be modified in the state. The "set" state refers to a parameter setting state in which the specification parameters and the functional parameters are allowed to be modified, welding cannot be started, and the CPU does not respond even if a welding start instruction is received.
The 'working' state and the 'setting' state are respectively indicated by the indicator light and switched by the 'working/setting' key. It is not switchable during welding.
8. Adjustment/welding mode
The controller has two modes of operation, adjustment and welding respectively. In the "adjustment" mode, only the welding process and the operation are executed, and the welding current is not output and is used for debugging the machine. The "welding" mode is a normal welding mode.
9. Single spot/continuous spot welding
The single spot welding or continuous spot welding can be selected according to different welding workpieces, and the single spot welding starts a welding instruction every time to weld one point. The continuous spot welding is to give a welding starting command once, and continuously weld N points until a welding stopping command is received.
10. Power distribution
When a user has a plurality of welding machines to work, but the capacity of the power grid does not allow simultaneous welding, the power distribution function can be used, and the function can lead each welding machine to carry out time-sharing welding, reasonably utilize the power grid resource and avoid overload accidents caused by simultaneous welding of a plurality of welding machines. This function needs to be used in conjunction with the power divider.
11. Fault diagnosis
When the system is detected to be abnormal, the CPU immediately stops the current work, sends the detected fault information to the touch screen for display, and prompts the fault information to a user through a display window, so that the user can conveniently know and process the fault in time.
12. Input/output actions
The input action comprises a starting signal, a specification selection signal, a thermal protection switch signal and the like, and the CPU makes corresponding instructions according to different received signals. The output action comprises an air valve control signal, a welding end signal and the like, and the CPU sends a corresponding output action signal according to the working condition.
The invention judges the current state by CPU after starting, if it is in the setting state, it waits for the user to set parameters, if it is in the working state, it waits for the starting signal, after the starting signal is detected, it executes the procedures of prepressing time, pressurizing time, etc. according to the parameters set by the specification, after the execution of the specification parameters is finished, the counter adds a count to judge whether it is continuous welding, if it is single welding, it ends the work and is in the waiting state. If the welding is continuous welding and no stop command is received, the welding is executed from the pressurization time of the current specification, otherwise, the work is finished and the welding enters a waiting state.
As shown in fig. 37, the specific process of the present invention includes the following steps:
(1) starting up
And (3) switching on the power supply, resetting the CPU through hardware, then carrying out self-checking and executing an initialization program, calling each parameter from the memory, then normally displaying and finishing startup.
(2) Determining the operating/setting state
After the startup is finished, the CPU starts to read the state saved by the shutdown machine, if the state before the shutdown is the 'working' state, the CPU turns to the 'working' state, and if the state before the shutdown is the 'setting' state, the CPU turns to the 'setting' state.
(3) Set state
In the "set" state, the user is waited to set or modify the parameters. In this state, even with a start welding signal, no response is made. After the parameter setting is finished, the manual mode needs to be switched to the working state through the working/setting key.
(4) Working state
In the "on" state, the CPU detects a start welding signal and immediately sets parameters to start welding according to specifications if the start welding signal is detected. In this state all parameters are locked and no parameter can be modified.
(5) Performing weld specifications
And after detecting the starting signal, the CPU starts to execute corresponding welding specification parameters, namely the prepressing time, the pressurizing time, the preheating time, the interval and other parameters.
(6) Counting
And after the execution of the welding standard parameters is finished, the counter is increased by one to finish one welding. If the conditions such as alarm or artificial termination in the midway occur in the welding process, the current welding is not abnormal, and the counting is not carried out.
(7) Single/continuous
And judging the parameter single time/continuous after the counting is finished, and stopping working and entering a waiting state if the parameter is single welding. If the welding state is in the continuous state, whether a welding ending instruction exists is continuously judged, if the welding ending instruction does not exist, the welding state is switched to the continuous welding state, the welding is executed from the pressurization time of the current specification, and the prepressing time executed in the first welding is skipped. And if the welding ending command is detected, stopping working and entering a waiting state.
Claims (10)
1. A controller of an inversion energy storage welding machine with a constant current control function is characterized in that a main loop of the inversion energy storage welding machine comprises a rectification circuit, the input end of the rectification circuit is connected with a power interface, the output end of the rectification circuit is connected with the input end of an inversion circuit through a filter circuit, and the output end of the inversion circuit is connected with a welding transformer, wherein the inversion circuit adopts a full-bridge inversion circuit, one bridge arm of the full-bridge inversion circuit is composed of an IGBT device VT1 and an IGBT device VT4, the other bridge arm of the full-bridge inversion circuit is composed of an IGBT device VT2 and an IGBT device VT3, and two bridge arms of the full-bridge inversion circuit are conducted in turn by taking T as a cycle; a current sensor is connected in series on a circuit between the output end of the inverter circuit and the welding transformer;
the controller comprises a main control unit, the main control unit is connected with the leakage current detection sensor through a leakage detection circuit, and is connected with the idle switch through an idle switch tripping control circuit; the main control unit obtains a leakage current value by sampling through a leakage current detection circuit and a leakage current detection sensor, compares the leakage current value with a set value, and controls an idle switch release through an idle switch release control circuit if the leakage current value exceeds the set value so as to cut off a three-phase input power supply input through a power interface;
the main control unit is connected with the current sensor through a current sampling circuit and controls the on or off of an IGBT device in the full-bridge inverter circuit through a trigger circuit; the main control unit acquires a current signal output by the inverter circuit through the current sampling circuit by using the current sensor, and controls the on or off of an IGBT device in the full-bridge inverter circuit through the trigger circuit according to the acquired current signal so as to realize constant current control; when constant current control is carried out, a user sets a current set value and welding time of required welding current through a man-machine interaction unit connected with a main control unit, the main control unit compares an actual current value corresponding to a current signal obtained through a current sampling circuit with the current set value, and if the actual current value is smaller than the current set value, the main control unit increases the duty ratio of an IGBT device in an inverter circuit through a trigger circuit to increase the actual current value; if the actual current value is larger than the current set value, the main control unit reduces the duty ratio of the IGBT device through the trigger circuit, so that the actual current value is reduced;
the main control unit is connected with a protection circuit, the protection circuit is simultaneously connected with the current sensor, the protection circuit judges whether the actual current value is overlarge by adopting a hardware comparison mode, and when the actual current value of the current signal output by the inverter circuit exceeds a specified value, the protection circuit gives an alarm; the control unit judges whether the protection circuit generates an alarm or not through the interrupt signal, when the protection circuit generates the alarm, the control unit detects the interrupt signal, determines that an overcurrent phenomenon occurs, immediately stops working, and sends alarm information to the human-computer interaction unit for displaying;
the main control unit also detects the direct current voltage rectified by the rectifying circuit through a voltage sampling circuit and displays the direct current voltage through the human-computer interaction unit.
2. The inverter energy storage welding machine controller with the constant current control function as claimed in claim 1, wherein the leakage detection circuit converts a leakage current signal detected by the leakage current sensor into an alternating current pulse voltage signal, and then converts the alternating current pulse voltage signal into a direct current pulse voltage signal, and the leakage detection circuit sends the direct current pulse voltage signal to the main control unit.
3. The inverter energy storage welding machine controller with the constant current control function as claimed in claim 2, wherein a release is installed on the idle switch, and the release is released immediately after the release is connected with a DC24V power supply.
4. The inverter energy storage welding machine controller with the constant current control function as claimed in claim 3, wherein the leakage detection circuit comprises an operational amplifier IC1-1, the non-inverting input end of the operational amplifier IC1-1 is connected with a resistor R19 and a resistor R20 which are connected in series, the resistor R20 is grounded, and the leakage current sensor is connected in parallel with the resistor R20; the inverting input terminal of the operational amplifier IC1-1 is grounded through a resistor R18; a diode Z13 and a diode Z12 which are connected in parallel are connected between the non-inverting input end and the inverting input end of the operational amplifier IC 1-1; the anode of the diode Z13 is connected with the non-inverting input end of the operational amplifier IC1-1, and the cathode of the diode Z13 is connected with the inverting input end of the operational amplifier IC 1-1; the cathode of the diode Z12 is connected with the non-inverting input end of the operational amplifier IC1-1, and the anode of the diode Z12 is connected with the inverting input end of the operational amplifier IC 1-1; the output end of the operational amplifier IC1-1 is connected with the inverting input end of the operational amplifier IC2-1 through a resistor R16; a resistor R17 is connected between the output end and the inverting input end of the operational amplifier IC1-1 in a bridging way;
the non-inverting input end of the operational amplifier IC2-1 is grounded; the diode Z10 is connected in series with the resistor R13 and then connected in parallel with the diode Z11 and the resistor R12 which are connected in series to form a parallel circuit, the parallel circuit is bridged between the output end and the inverting input end of the operational amplifier IC2-1, the anode of the diode Z10 and the cathode of the diode Z11 are connected with the output end of the operational amplifier IC2-1, the cathode of the diode Z10 is connected with the resistor R13, and the anode of the diode Z11 is connected with the resistor R12;
the non-inverting input end of the operational amplifier IC2-2 is connected with the cathode of the diode Z10; the inverting input end of the operational amplifier IC2-2 is connected with the anode of a diode Z11 through a resistor R14; the output end of the operational amplifier IC2-2 is connected with the A/D conversion input end of the main control unit; a resistor R11 is connected across the output terminal and the inverting input terminal of the operational amplifier IC 2-2.
5. The inverter energy storage welding machine controller with the constant current control function as claimed in claim 4, wherein the idle tripping control circuit comprises a transistor Q2 and an optical coupler IC1, wherein:
the emitter of the transistor Q2 is connected with a constant voltage source; the base electrode of the transistor Q2 is connected with the control signal output end of the main control unit through a resistor R1; the collector of the transistor Q2 is grounded via a resistor R2 and a light emitting diode Z1 which are connected in series, and the collector of the transistor Q2 is connected with the primary side of the optocoupler IC1 via a resistor R3;
the secondary side of the optocoupler IC1 is bridged between the base and the collector of the transistor Q1, the emitter of the transistor Q1 is grounded, the collector of the transistor Q1 is connected with the relay J1, and the relay J1 is connected with a diode Z2 in parallel; after the relay J1 is electrified and sucked, a normally open contact J1-1 of the relay J1 is switched on, and a release is switched on a DC24V power supply, so that the idle switch is released; after the relay J1 loses power, the normally open contact J1-1 of the relay J1 is opened, and the tripper is disconnected with the DC24V power supply.
6. The inverter energy storage welding machine controller with the constant current control function according to claim 1, wherein after welding is started, when the main control unit performs constant current control, the following steps are adopted to obtain the turn-on time of an IGBT device in the inverter circuit of each period T so as to adjust the duty ratio:
step 1, enabling an IGBT device to be turned on for 20% of a half period T/2 in a current period, simultaneously enabling the main control unit to continuously sample output current of the inverter circuit for N times through the current sensor and the current sampling circuit, comparing the current sampling current with the current sampled at the previous time, and calculating the rising rate of the current;
step 2, calculating the root mean square value of the sampled N-point current to obtain an effective value Irms of the welding current, wherein the calculation formula is as follows:
in the formula InRepresenting the current value obtained by the nth sampling;
step 3, the main control unit predicts the required turn-on time of the corresponding IGBT device when the actual current value is equal to the current set value according to the effective value Irms obtained by calculation, and the required turn-on time is used as the turn-on time of the IGBT in the next period;
and 4, continuously sampling the output current of the inverter circuit for N times in the next period, correcting the rising rate of the current obtained by calculation in the previous period, and returning to the step 2 until the welding time is reached.
7. The inverter energy storage welding machine controller with the constant current control function as claimed in claim 1, wherein the filter circuit adopts a film capacitor.
8. The inverter energy storage welding machine controller with the constant current control function as claimed in claim 1, wherein the rectifying circuit, the filter circuit and the inverter circuit are connected into a whole through a laminated busbar, and the loop is shortest.
9. The inverter energy storage welding machine controller with the constant current control function according to claim 1, wherein the rectifying circuit and the inverter circuit are mounted on a radiator together, wherein the radiator comprises an aluminum plate, an O-shaped groove is formed in the back surface of the aluminum plate by adopting a CNC (computerized numerical control) process, the O-shaped groove is in a U shape on the aluminum plate, a copper pipe is embedded into the O-shaped groove, a heat-conducting glue containing metal powder is used for filling a gap, the surface is finally ground flat by a grinding machine, and the copper pipe is connected with a water way joint outside the inverter energy storage welding machine controller; the rectifier circuit and the inverter circuit are fixed on the front face of the aluminum plate, heat conducting grease is coated on the contact surface of the high-power semiconductor device in the rectifier circuit and the inverter circuit and the aluminum plate, the high-power semiconductor device is fully contacted with the radiator, cooling water flows through the copper tube, and heat in the aluminum plate is taken away through the copper tube.
10. The inverter energy storage welding machine controller with the constant current control function as claimed in claim 1, wherein the control unit is connected with a memory, 32 welding specifications are preset in the memory, and different welding specifications can be set for different welding points through the human-computer interaction unit;
the control unit is also connected with the signal output interface through the action output unit and is connected with the signal input interface through the action input unit.
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Application publication date: 20210309 |