Arc power supply system and arc power supply based on trapezoidal wave signal

Abstract

The present invention discloses an arc power supply system and an arc power supply based on a trapezoidal wave signal, wherein the arc power supply system comprises: a control system and a power conversion circuit; wherein the power conversion circuit comprises: a transformer, a rectifier and an inverter; the primary winding of the transformer is connected to an AC power grid; the secondary winding of the transformer is connected to an AC input terminal of the rectifier; the DC output terminal of the rectifier is connected to a DC input terminal of an inverter through a DC bus; the AC output terminal of the inverter is connected to an arc device; a control system is respectively connected to the power conversion circuit and the arc device, and is used to collect the arc voltage or arc current of the arc device, and according to the arc voltage or arc current of the arc device, control the inverter in the power conversion circuit to output a trapezoidal wave voltage signal that meets the arc stable burning condition. The present invention can provide a trapezoidal wave AC signal required for the arc device to stably burn the arc without the need to connect an inductor in series to the power supply circuit.

Description

Technical Field

[0001] The invention relates to the field of arc power supply, and in particular to an arc power supply system and an arc power supply based on a trapezoidal wave signal. Background Art

[0002] This section is intended to provide a background or context to the embodiments of the invention recited in the claims. No admission is made that the description herein is prior art by inclusion in this section.

[0003] AC arc heating is widely used in arc equipment such as AC arc furnaces and electric welders, because the AC power supply changes periodically (50 times per second) from zero, positive maximum value, zero, reverse maximum value, and zero according to its frequency (for example, 50Hz). Figure 1 A waveform diagram of arc voltage and current changing with time provided in the prior art, such as Figure 1 As shown, since the impedance characteristics of the AC arc itself are nonlinear, a certain initial voltage (i.e., arc ignition voltage Ui) is required to ignite the arc. The burning arc voltage Ua decreases as the current Ia increases (negative impedance characteristics) until the arc voltage decays to a certain voltage (arc extinction voltage Ue) and the arc is extinguished.

[0004] At present, it is generally believed in the industry that AC arcs have nonlinear resistance characteristics. In a purely resistive circuit or one with insufficient inductance, due to the close phases of current and voltage, during the arc burning process, the arc is frequently ignited and extinguished at twice the frequency of the AC power supply (for example, 50Hz), and the arc cannot burn continuously. In order to achieve the purpose of stable burning of the AC arc, the existing arc power supply circuit connects an inductor in series in the arc power supply loop (the inductance value is generally not less than 30% of the standard value based on the loop capacity). At the moment of arc extinguishing, due to the large rate of change of current, a high induced voltage will be generated at both ends of the inductor. The induced voltage is greater than the arc burning voltage after being superimposed on the power supply voltage, so that the arc current is continuous and uninterrupted, so as to achieve the purpose of stable arc burning. Figure 2 The waveforms shown are the arc voltage and current changing with time after an inductor is connected in series in the power supply circuit of the arc equipment.

[0005] Figure 3 The arc power supply circuit with an inductor in series is shown, Figure 3 As shown, inserting an inductor in series in the arc power supply circuit will cause the current phase of the power supply circuit to lag behind the system voltage, resulting in a lower overall power factor of the power supply circuit, increased active power loss, and lower power efficiency.

[0006] To address the above problems, no effective solution has been proposed yet. Summary of the invention

[0007] The embodiment of the present invention provides an arc power supply system based on a trapezoidal wave signal, which is used to solve the technical problem that an inductor is connected in series in the power supply circuit of the existing arc power supply system to provide alternating current for stable arc burning. Since the inductor causes the current in the power supply circuit to have hysteresis, the overall power factor of the power supply circuit becomes low, the active power loss increases, and the power efficiency becomes low. The arc power supply system includes: a control system and a power conversion circuit; wherein the power conversion circuit includes: a transformer, a rectifier and an inverter; the primary winding of the transformer is connected to the AC power grid; the secondary winding of the transformer is connected to the AC input end of the rectifier; the DC output end of the rectifier is connected to the DC input end of the inverter through a DC bus; the AC output end of the inverter is connected to the arc equipment; the control system is respectively connected to the power conversion circuit and the arc equipment, and is used to collect the arc voltage or arc current of the arc equipment, and according to the arc voltage or arc current of the arc equipment, control the inverter in the power conversion circuit to output a trapezoidal wave voltage signal that meets the conditions for stable arc burning.

[0008] An embodiment of the present invention also provides an arc power supply to solve the technical problem that an inductor is connected in series in the power supply circuit of the existing arc power supply system to provide alternating current for stable arc burning. Since the inductor causes the current in the power supply circuit to have lag, the overall power factor of the power supply circuit becomes low, the active power loss increases, and the power efficiency becomes low. The arc power supply includes: the above-mentioned arc power supply system based on trapezoidal wave signal.

[0009] In an embodiment of the present invention, the AC power of the AC power grid is converted into the AC power required by the arc device through a power converter composed of a transformer, a rectifier and an inverter. The control system collects the arc voltage or arc current of the arc device, and controls the inverter in the power conversion circuit to output a trapezoidal wave voltage signal that meets the stable burning conditions of the arc according to the arc voltage or arc current of the arc device.

[0010] The arc power supply system and arc power supply provided by the embodiments of the present invention can provide a trapezoidal wave AC signal required for the arc equipment to stably burn the arc without the need for a series inductor. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0012] Figure 1 A schematic diagram of the waveforms of arc voltage and current changing with time provided in the prior art;

[0013] Figure 2 A schematic diagram of waveforms of arc voltage and current changing with time after an inductor is connected in series in a power supply circuit of an arc device provided in the prior art;

[0014] Figure 3 A schematic diagram of an arc power supply circuit provided in the prior art;

[0015] Figure 4 A schematic diagram of an arc power supply system based on a trapezoidal wave signal provided in an embodiment of the present invention;

[0016] Figure 5 A schematic diagram of a trapezoidal wave voltage signal provided by an embodiment of the present invention;

[0017] Figure 6 A schematic diagram of an optional arc power supply system provided in an embodiment of the present invention;

[0018] Figure 7 A schematic diagram of an optional voltage signal conversion circuit provided by an embodiment of the present invention;

[0019] Figure 8 A schematic diagram of an optional current signal conversion circuit provided by an embodiment of the present invention;

[0020] Fig. 9 A schematic diagram of an optional DC bus voltage signal acquisition circuit provided in an embodiment of the present invention;

[0021] Fig.10 A schematic diagram of the connection between a gear position control signal output circuit and a transformer provided in an embodiment of the present invention;

[0022] Fig.11 A schematic diagram of a connection between a rectification control signal output circuit and a rectifier provided in an embodiment of the present invention;

[0023] Fig.12 A schematic diagram of the connection between an inverter control signal output circuit and an inverter provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0025] In the description of this specification, the terms "include", "including", "have", "contain", etc. are all open terms, which mean including but not limited to. The descriptions with reference to the terms "one embodiment", "a specific embodiment", "some embodiments", "for example", etc. mean that the specific features, structures or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. The order of steps involved in each embodiment is used to schematically illustrate the implementation of the present application, and the order of steps is not limited and can be appropriately adjusted as needed.

[0026] An embodiment of the present invention provides an arc power supply system based on a trapezoidal wave signal. Figure 4 A schematic diagram of an arc power supply system based on a trapezoidal wave signal provided by an embodiment of the present invention, such as Figure 4 As shown, the arc power supply system includes: a control system 10 and a power conversion circuit 20;

[0027] The power conversion circuit includes: a transformer 201, a rectifier 202 and an inverter 203; the primary winding of the transformer is connected to the AC power grid; the secondary winding of the transformer 201 is connected to the AC input terminal of the rectifier 202; the DC output terminal of the rectifier 202 is connected to the DC input terminal of the inverter 203 through a DC bus; the AC output terminal of the inverter 203 is connected to the arc device 30;

[0028] The control system 10 is connected to the power conversion circuit 20 and the arc device 30 respectively, and is used to collect the arc voltage or arc current of the arc device 30, and according to the arc voltage or arc current of the arc device 30, control the inverter 203 in the power conversion circuit 20 to output a trapezoidal wave voltage signal that meets the arc stable combustion conditions.

[0029] It should be noted that in the arc power supply system provided by the embodiment of the present invention, the control system 10 can be used to realize but not limited to the following functions: ① Data acquisition: collect the primary / secondary voltage of the transformer, the position of the voltage regulating switch, and collect the DC bus voltage, the current and voltage value on the inverter output side. ② Control function: control the position of the transformer voltage regulating switch to obtain the desired DC bus voltage and power factor on the power supply side; control the trigger angle of the rectifier to obtain the desired DC bus voltage; control the waveform, amplitude, and frequency adjustment of the inverter output voltage to complete the stability of the arc and arc power control.

[0030] like Figure 4As shown, the power conversion circuit 20 is composed of a transformer 201, a rectifier 202 and an inverter 203. Among them, the transformer can convert the standard AC voltage value of the system into the voltage value required by the rectifier according to the transformation ratio, and the voltage value can be a fixed value or an adjustable value within a certain range; the rectifier can convert the secondary voltage of the transformer into a DC voltage in the form of controllable or uncontrollable rectification; the inverter can convert the DC voltage into the voltage waveform, amplitude, and frequency required for the normal and stable burning of the arc, and control the output current value to meet the arc power requirements.

[0031] Optionally, the waveform of the inverter output voltage may be any one of, but not limited to, a rectangular wave, a trapezoidal wave, a fitted wave composed of a broken line or a curve, etc. The amplitude of the inverter output voltage should meet the voltage value required for stable arc burning, and its modulation method includes but is not limited to any one of the following, or a combination of any two or three: ① The voltage value on the DC side is adjusted through a transformer or rectifier, the inverter side does not adjust the voltage amplitude, and only changes the voltage direction once every half cycle; ② The voltage of the DC bus remains unchanged, and the inverter side is turned on and off multiple times within a half cycle to adjust the on-state voltage time width ratio on the output side; ③ A multi-level inverter is used to modulate the voltage amplitude according to the arc length requirements.

[0032] In one embodiment, the frequency of the amplitude of the inverter output voltage can be varied within a lower (eg, lower than 10 Hz) and higher (eg, higher than 100 Hz) frequency range, and the adjustment method can be to change the voltage direction on the inverter output side.

[0033] It should be noted that the DC voltage output by the rectifier can be adjusted within a certain range. The adjustment methods include but are not limited to: ① adjusting the secondary voltage of the transformer by changing the transformer ratio; ② changing the trigger angle of the rectifier to adjust the conduction time of the rectifier.

[0034] It should be noted that, in order to make the inverter output a trapezoidal wave voltage signal that meets the arc stable burning condition, the DC voltage at the DC input terminal of the inverter can be controlled, or the voltage at the AC output terminal of the inverter can be controlled. Therefore, in order to provide a trapezoidal wave voltage signal that meets the arc stable burning condition, the embodiment of the present invention can be implemented by but not limited to any of the following methods, or a combination of the following methods:

[0035] In the first implementation mode, the position of the voltage regulating switch on the transformer is controlled by the control system so that the inverter outputs a trapezoidal wave voltage signal that satisfies the arc stable burning condition. Optionally, in this implementation mode, the control system is also used to collect the primary voltage and secondary voltage of the transformer, and determine the position of the voltage regulating switch on the transformer according to the primary voltage and secondary voltage of the transformer.

[0036] In a second implementation mode, the trigger angle conduction time of the rectifier is controlled by a control system so that the inverter outputs a trapezoidal wave voltage signal that satisfies the arc stable burning condition. Optionally, in this implementation mode, the control system is also used to collect the AC voltage at the AC input end of the rectifier and the DC voltage at the DC output end, and determine the trigger angle conduction time of the rectifier according to the AC voltage at the AC input end of the rectifier and the DC voltage at the DC output end.

[0037] In a third implementation mode, the voltage duty ratio of the inverter output voltage signal is controlled by the control system so that the inverter outputs a trapezoidal wave voltage signal that satisfies the arc stable burning condition. Optionally, in this implementation mode, the control system is also used to collect the DC voltage at the DC input terminal of the inverter and the AC voltage at the AC output terminal, and determine the voltage duty ratio of the inverter output voltage signal based on controlling the DC voltage at the DC input terminal of the inverter and the AC voltage at the AC output terminal.

[0038] It should be noted that in order to achieve frequency regulation of the inverter output voltage signal, the direction of the inverter output voltage signal may be changed by the control system.

[0039] Figure 5 A schematic diagram of a trapezoidal wave voltage signal provided by an embodiment of the present invention, such as Figure 5 As shown, the arc power supply system provided by the embodiment of the present invention, when the control system 10 controls the inverter in the power conversion circuit 20 to output a trapezoidal wave voltage signal that meets the arc stable combustion condition, can control the inverter device in the power conversion circuit 20 to output the following voltage signal U in each voltage modulation cycle through the control system 10:

[0040]

[0041] Among them, t1 is the moment when the arc current decays to zero in the previous voltage modulation cycle; t2 is the moment when the arc current rises from zero to the maximum positive current value; t3 is the moment when the arc current starts to decay from the maximum positive current value; t4 is the moment when the arc voltage decays from the maximum positive voltage value to zero; t5 is the moment when the arc current decays from the maximum positive voltage value to zero; t6 is the moment when the arc current decays from zero to the maximum negative current value; t7 is the moment when the arc current starts to rise from the maximum negative current value; t8 is the moment when the arc voltage rises from the maximum negative voltage value to zero; t9 is the moment when the arc current rises from the maximum negative current value to zero, f is the frequency of the trapezoidal wave voltage signal.

[0042] Each stage is described in detail below.

[0043] ① In the 0~t1 stage, the voltage output is 0, waiting for the arc current to gradually decay to 0 in the previous voltage modulation cycle; t1 is related to parameters such as the reactor, arc equivalent resistance, and arc equivalent reactance, and is one of the key parameters for stabilizing the arc.

[0044] ②In the stage t1-t2, the voltage output is a linear increasing process. This stage is the process of the reactor gradually forming a stable maximum current. The purpose is to prevent the voltage from changing too quickly. The reactor is a large inductor, and the current flowing through its two ends cannot change quickly. The specific maximum value of the change is related to the parameters of the reactor. If the voltage increases too quickly, the reactor will enter the electromagnetic saturation area, generate nonlinear current, and the arc voltage will not meet expectations.

[0045] ③ In the stage of t2-t3, the voltage output is a stable value M. In this stage, the forward arc is established quickly, and the arc current maintains the maximum positive value. The more stable the voltage output is, the more continuous the change of the arc current is. It is also the process of rapid conversion of electrical energy into arc heat. It is an optimized method to stabilize the arc and increase the arc transmission power.

[0046] ④ In the stage of t3-t4, the voltage gradually decreases and the current in the reactor gradually decays to 0. The decreasing process needs to be set in conjunction with the reactor parameters. The most ideal control result is that the voltage and current reach 0 at the same time at t4.

[0047] ⑤ In the stage of t4-t5, the voltage output is 0. Wait for the arc current in the stage of t1-t4 to gradually decay to 0; similar to the stage of 0-t1. Due to the uncertainty of the system equivalent resistance and equivalent reactance, including the coupling between the three phases of the system, the current may not be zero at time t4, and it is necessary to control the voltage output to 0 in the stage of t4-t5.

[0048] ⑥In the stage t5~t6, the voltage gradually decreases from 0 to a stable value -M, similar to the stage t1~t2.

[0049] ⑦ In the stage of t6~t7, the voltage output is a stable value -M. In this stage, the negative arc is quickly established, and the arc current maintains the negative maximum value, which is similar to the stage of t2~t3.

[0050] ⑧In the stage of t7~t8, the voltage output gradually increases from the stable value -M to 0, similar to the stage of t3~t4.

[0051] ⑨ In the stage of t8-t9, the voltage output is 0, waiting for the arc current in the stage of t5-t8 to gradually decay to 0; similar to the stage of 0-t1.

[0052] Figure 6 A schematic diagram of an optional arc power supply system provided in an embodiment of the present invention, such as Figure 6As shown, in the arc power supply system, the control system 10 includes: a controller 100, an arc voltage / current signal acquisition circuit 101, an inverter control signal output circuit 102 and a DC bus voltage signal acquisition circuit 103; the arc voltage / current signal acquisition circuit 101 is connected between the controller 100 and the arc device 30, and is used to transmit the arc voltage / current signal of the arc device 30 to the controller 100; the DC bus voltage signal acquisition circuit 103 is connected between the controller 100 and the DC bus, and is used to transmit the DC voltage signal of the DC bus to the controller 100; the inverter control signal output circuit 102 is connected between the controller 100 and the inverter 203, and is used to transmit the inverter control signal output by the controller 100 to the inverter 203.

[0053] Since the electrical signals (voltage / current signals) in the power conversion circuit are all high-voltage electrical signals, and the electrical signals (voltage / current signals) required by the controller in the control system are all low-voltage electrical signals, therefore, as an optional implementation, in the power supply circuit provided in the embodiment of the present invention, the arc voltage / current signal acquisition circuit 101 includes: a first voltage / current transformer, connected between the controller 100 and the arc device 30, for converting the high-voltage electrical signal output by the arc device 30 into the low-voltage electrical signal required by the controller 100. The voltage transformer in the arc voltage / current signal acquisition circuit 101 can realize the conversion of the high-voltage voltage signal into the low-voltage voltage signal.

[0054] Figure 7 A schematic diagram of an optional voltage signal conversion circuit provided by an embodiment of the present invention, such as Figure 7 As shown, the high-voltage cable has a total of 3 power supply cables, namely phases A, B, and C. Using a voltage transformer as a detection component, the high-voltage voltage signal can be attenuated into a low-voltage voltage signal (for example, a 100V voltage signal), and the voltage signal acquisition circuit is used to collect and input it into the controller. The signal input side of the voltage transformer has 6 signal lines, and the signal output side has 3 signal lines. Through the 3 signal lines on the signal output side of the voltage transformer, the 3 high-voltage voltage signals are transmitted to the voltage signal acquisition circuit to obtain the 3 low-voltage voltage signals. That is, the first voltage transformer converts the high-voltage voltage signals Ua, Ub, and Uc of the arc equipment into low-voltage voltage signals PT3-A, PT3-B, and PT3-C.

[0055] Figure 8 A schematic diagram of an optional current signal conversion circuit provided by an embodiment of the present invention, such as Figure 8As shown, the high-voltage cable has a total of 3 power supply cables, namely phases A, B, and C. With the current transformer as the detection component, the high-voltage current signal can be attenuated into a low-voltage current signal (for example, a 1A current signal), and the signal is collected and input to the controller through the current signal acquisition circuit. The signal input side of the current transformer has 6 signal lines, and the signal output side has 6 signal lines. Through the 6 signal lines on the signal output side of the current transformer, the 3 high-voltage current signals are transmitted to the current signal acquisition circuit to obtain 6 low-voltage current signals. That is, the first current transformer converts the high-voltage current signals Ia, Ib, and Ic of the arc equipment into low-voltage current signals CT-A1, CT-A2, CT-B1, CT-B2, CT-C1, and CT-C2.

[0056] Fig. 9 A schematic diagram of an optional DC bus voltage signal acquisition circuit provided by an embodiment of the present invention, such as Fig. 9 As shown, the DC bus voltage detection is to detect the rectifier output voltage, which is charged through the DC capacitor and converted into a DC power. The high-voltage DC voltage is attenuated into a low-voltage DC power (for example, 0 to +10V voltage) through the DC bus voltage detection board, and transmitted to the DC bus voltage signal acquisition circuit in the form of analog quantity through channels AO-1 and AO-2. The DC bus voltage signal acquisition circuit collects the DC bus voltage through analog output channels AI-1 and AI-2.

[0057] Fig.10 A schematic diagram of a connection between a gear position control signal output circuit and a transformer provided in an embodiment of the present invention is shown in FIG. Fig.10 As shown, the three signal lines (DO-01, DO-02 and DO-03) of the gear control signal output circuit are connected to the three signal lines (DI-01, DI-02 and DI-03) of the transformer voltage regulating switch.

[0058] Since the DC voltage signal of the DC bus in the power conversion circuit is also a high-voltage signal, in an optional implementation, the power supply circuit provided in the embodiment of the present invention may also include: a DC bus voltage detection board, connected between the DC bus voltage signal acquisition circuit 103 and the DC bus, for converting the high-voltage DC signal of the DC bus into a low-voltage DC signal of the controller 100.

[0059] Therefore, in an optional embodiment, the power supply circuit provided in the embodiment of the present invention may further include: a rectifier control signal output circuit 104, connected between the controller 100 and the rectifier 202, and used to transmit the rectifier control signal output by the controller 100 to the inverter 203. Optionally, the rectifier control signal output circuit 104 transmits the rectifier control signal output by the controller 100 to the inverter 203 via an optical fiber.

[0060] Fig.11 A schematic diagram of a connection between a rectifier control signal output circuit and a rectifier provided in an embodiment of the present invention is shown in FIG. Fig.11 As shown, the control system controls the rectifier through two plastic optical fibers, Fib-Tx represents the sending signal optical fiber, and Fib-Rx represents the receiving signal optical fiber.

[0061] Preferably, in the power supply circuit provided by the embodiment of the present invention, the inverter control signal output circuit 102 transmits the inverter control signal output by the controller 100 to the inverter 203 via an optical fiber. Fig.12 A schematic diagram of a connection between an inverter control signal output circuit and an inverter provided by an embodiment of the present invention is shown in FIG. Fig.12 As shown, the control system controls the inverter through two plastic optical fibers, Fib2-Tx represents the sending signal optical fiber, and Fib2-Rx represents the receiving signal optical fiber.

[0062] As can be seen from the above, the arc power supply system provided by the embodiment of the present invention converts the AC power of the AC power grid into the AC power required by the arc device through the power converter 20 composed of the transformer 201, the rectifier 202 and the inverter 203, and the arc voltage / current signal acquisition circuit 101 in the control system 10 acquires the voltage / current signal of the arc device 30, and the DC bus voltage signal acquisition circuit 103 in the control system acquires the DC voltage signal input from the rectifier 202 to the inverter 203 in the power converter; the controller 100 in the control system 10 outputs the control signal of the inverter 203, and transmits it to the inverter 203 through the inverter control signal output circuit 102, so as to realize the control of the inverter 203 outputting the AC signal, so that it meets the AC power required for the arc device to continuously burn the arc. It can be seen that the arc power supply system provided by the embodiment of the present invention can provide the AC signal (for example, a trapezoidal wave AC signal) required to meet the stable burning of the arc of the arc device without the need to connect the inductor in series.

[0063] In an optional embodiment, the power supply circuit provided by the embodiment of the present invention may also include: a primary voltage / current signal acquisition circuit 105, connected between the controller 100 and the primary winding of the transformer 201, and used to transmit the primary voltage / current signal of the transformer 201 to the controller 100; a secondary voltage / current signal acquisition circuit 107, connected between the controller 100 and the secondary winding of the transformer 201, and used to transmit the secondary voltage / current signal of the transformer 201 to the controller 100; a gear control signal output circuit 106, connected between the controller 100 and the voltage regulating switch of the transformer 201, and used to transmit the gear control signal output by the controller 100 to the voltage regulating switch.

[0064] Optionally, in the power supply circuit provided in an embodiment of the present invention, the primary voltage / current signal acquisition circuit 105 includes: a second voltage / current transformer, connected between the controller 100 and the transformer 201, and used to convert the high-voltage electrical signal output from the primary side of the transformer 201 into a low-voltage electrical signal required by the controller 100; the secondary voltage / current signal acquisition circuit 107 includes: a third voltage / current transformer, connected between the controller 100 and the transformer 201, and used to convert the high-voltage electrical signal output from the secondary side of the transformer 201 into a low-voltage electrical signal required by the controller 100.

[0065] It should be noted that the implementation of the primary voltage / current signal acquisition circuit 105 and the secondary voltage / current signal acquisition circuit 107 is the same as that of the arc voltage / current signal acquisition circuit 101 .

[0066] The primary side voltage detection and the secondary side voltage detection are consistent with the arc voltage detection. The second voltage transformer converts the high-voltage voltage signals Ua, Ub, and Uc on the primary side of the transformer into low-voltage voltage signals PT-A, PT-B, and PT-C; the third voltage transformer converts the high-voltage voltage signals Ua, Ub, and Uc on the secondary side of the transformer into low-voltage voltage signals PT2-A, PT2-B, and PT2-C.

[0067] Similarly, the primary side current detection and the secondary side current detection are consistent with the arc current detection. The second current transformer converts the high-voltage current signals Ia, Ib, and Ic on the primary side of the transformer into low-voltage current signals CT-A1, CT-A2, CT-B1, CT-B2, CT-C1, and CT-C2. The third current transformer converts the high-voltage current signals Ia, Ib, and Ic on the secondary side of the transformer into low-voltage current signals CT2-A1, CT2-A2, CT2-B1, CT2-B2, CT2-C1, and CT2-C2.

[0068] The embodiment of the present invention also provides an arc power supply to solve the technical problem that an inductor is inserted in series in the power supply circuit of the existing arc power supply system to provide alternating current for stable arc burning. Since the inductor causes the current in the power supply circuit to have hysteresis, the overall power factor of the power supply circuit becomes low, the active power loss increases, and the power efficiency becomes low. The arc power supply includes: the above-mentioned arc power supply system based on trapezoidal wave signal. Since the principle of solving the problem of the arc power supply embodiment is similar to that of the above-mentioned arc power supply system based on trapezoidal wave signal, the implementation of the arc power supply embodiment can refer to the implementation of the above-mentioned arc power supply system based on trapezoidal wave signal, and the repeated parts will not be repeated.

[0069] It should be noted that the arc power supply provided in the embodiment of the present invention can be used as, but not limited to, a power supply for arc-type electrical equipment such as an arc furnace and an electric welder.

[0070] It should be noted that the customized power supply provided in the embodiment of the present invention can meet the stable operation of arc equipment, and the characteristics of its output voltage and current are as follows:

[0071] ① Different from the AC sinusoidal waveform of a standard power supply, the embodiment of the present invention adopts waveform modulation technology to modulate the voltage waveform into one of rectangular, trapezoidal, or other curve-fitted alternating voltage waveforms, which is proportional to the wave required for arc burning.

[0072] ② To match the zero-crossing point of the arc current, the zero-crossing point of the alternating voltage waveform is controlled by du / dt, and the slope of the voltage waveform (trapezoidal, other curve-fitting voltage waveform) is greater than the value required for the arc current to be continuous.

[0073] ③ The amplitude of the output voltage meets the requirement for stable burning of the arc with the corresponding arc length.

[0074] ④ The output alternating voltage waveform frequency can be adjusted within the range of 10 to 100 Hz to meet the minimum loss and optimal power factor requirements of the circuit.

[0075] ⑤Control the set current value to be constant to meet the required arc power value.

[0076] The embodiment of the present invention adopts customized power supply technology based on the study of the volt-ampere characteristics of electric arc, and customizes power supply specifically for electric arc electrical equipment to meet the requirements for stable operation of such equipment.

[0077] In summary, the embodiment of the present invention provides a power supply system and power supply for an arc device, wherein a power converter is connected to an AC power grid through a rectifier transformer, converts the AC power of the AC power grid into the AC power required by the rectifier, and then converts the AC power into DC power through a rectifier, and converts the DC power output by the rectifier into the AC power required by the arc device to burn the arc through an inverter, and the control system controls the inverter in the power converter to output a trapezoidal wave voltage signal that meets the conditions for stable arc burning, so as to achieve the purpose of continuously and uninterruptedly burning the arc of the arc device. Since the embodiment of the present invention does not need to insert an inductor in series in the power supply circuit, it can avoid the problem that the overall power factor of the power supply circuit becomes low, the active power loss increases, and the power efficiency becomes low due to the insertion of an inductor in the existing arc power supply circuit.

[0078] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An arc power supply system based on a trapezoidal wave signal, characterized in that: include: Control systems and power conversion circuits; The power conversion circuit includes: a transformer, a rectifier and an inverter; the primary winding of the transformer is connected to the AC power grid; the secondary winding of the transformer is connected to the AC input terminal of the rectifier; the DC output terminal of the rectifier is connected to the DC input terminal of the inverter through a DC bus; the AC output terminal of the inverter is connected to the arc device; The control system is connected to the power conversion circuit and the arc device respectively, and is used to collect the arc voltage or arc current of the arc device, and control the inverter in the power conversion circuit to output a trapezoidal wave voltage signal that meets the arc stable combustion condition according to the arc voltage or arc current of the arc device; The transformer is used to convert the standard AC voltage value of the system into the voltage value required by the rectifier according to the transformation ratio; the rectifier is used to convert the secondary voltage of the transformer into a DC voltage through controllable or uncontrollable rectification; the inverter is used to convert the DC voltage into the voltage waveform, amplitude, and frequency required for normal and stable burning of the arc, and control the output current value to meet the arc power requirements; The modulation method of the amplitude of the inverter output voltage includes one of the following or any combination: The voltage value on the DC side is adjusted by a transformer or rectifier, the voltage amplitude is not adjusted on the inverter side, and the voltage direction is changed every half cycle; The voltage of the DC bus remains unchanged, and the on-state voltage time ratio of the output side is adjusted by switching the inverter side on and off multiple times within half a cycle; Use a multi-level inverter to modulate the voltage amplitude according to the arc length requirements; The rectifier output DC voltage adjustment method includes one of the following or any combination: Adjust the transformer's secondary voltage by changing the transformer's transformation ratio; Changing the trigger angle of the rectifier adjusts the conduction time of the rectifier; The control system controls the inverter in the power conversion circuit to output the following voltage signal U in each voltage modulation cycle: Among them, t1 is the moment when the arc current decays to zero in the previous voltage modulation cycle; t2 is the moment when the arc current rises from zero to the maximum positive current value; t3 is the moment when the arc current starts to decay from the maximum positive current value; t4 is the moment when the arc voltage decays from the maximum positive voltage value to zero; t5 is the moment when the arc current decays from the maximum positive voltage value to zero; t6 is the moment when the arc current decays from zero to the maximum negative current value; t7 is the moment when the arc current starts to rise from the maximum negative current value; t8 is the moment when the arc voltage rises from the maximum negative voltage value to zero; t9 is the moment when the arc current rises from the maximum negative current value to zero, f is the frequency of the trapezoidal wave voltage signal.

2. The arc power supply system according to claim 1, characterized in that: The control system is used to control the position of the voltage regulating switch on the transformer so that the inverter outputs a trapezoidal wave voltage signal that meets the arc stable burning condition.

3. The arc power supply system according to claim 2, characterized in that: The control system is also used to collect the primary voltage and the secondary voltage of the transformer, and determine the position of the voltage regulating switch on the transformer according to the primary voltage and the secondary voltage of the transformer.

4. The arc power supply system according to claim 1, characterized in that: The control system is used to control the trigger angle conduction time of the rectifier so that the inverter outputs a trapezoidal wave voltage signal that meets the arc stable combustion condition.

5. The arc power supply system according to claim 4, characterized in that: The control system is also used to collect the AC voltage at the AC input end and the DC voltage at the DC output end of the rectifier, and determine the trigger angle conduction time of the rectifier according to the AC voltage at the AC input end and the DC voltage at the DC output end of the rectifier.

6. The arc power supply system according to claim 1, characterized in that: The control system is used to control the voltage duty ratio of the inverter output voltage signal so that the inverter outputs a trapezoidal wave voltage signal that meets the arc stable combustion condition.

7. The arc power supply system according to claim 6, characterized in that: The control system is also used to collect the DC voltage at the DC input terminal and the AC voltage at the AC output terminal of the inverter, and determine the voltage duty ratio of the inverter output voltage signal based on controlling the DC voltage at the DC input terminal and the AC voltage at the AC output terminal of the inverter.

8. The arc power supply system according to claim 1, characterized in that: The control system is also used to adjust the frequency of the inverter output voltage signal by changing the direction of the inverter output voltage signal.

9. An arc power supply, characterized in that: include: An arc power supply system based on a trapezoidal wave signal as described in any one of claims 1 to 8.

Images