CN110328419B - Non-resistance electric spark pulse power supply and machining and gap discharge state identification method thereof - Google Patents
Non-resistance electric spark pulse power supply and machining and gap discharge state identification method thereof Download PDFInfo
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Abstract
The invention discloses a resistance-free medium-speed wire-passing pulse power supply and a processing and gap discharge state identification method thereof, wherein the circuit comprises a power loop, a driving circuit, an FPGA controller, a voltage detection circuit and a current detection circuit, when a first switching tube is conducted to a maximum waiting breakdown time threshold value, gap voltage in the time period is detected to calculate average voltage, and if the average voltage is no-load voltage, the gap is identified to be in a no-load state; otherwise, after the first switch tube is disconnected and the dead time is up, when the second switch tube is connected, the change of the falling slope of the gap current calculation current is detected, if the slope change rate exceeds the threshold value of the falling slope change rate, the gap is identified as a short circuit, and if the slope is almost unchanged or the change is small, the gap is identified as normal discharge; providing necessary basis for the feeding direction and speed of the servo system according to the identified gap state. The invention improves the identification precision of the discharge state of the power supply gap, and further improves the power supply processing efficiency and the discharge rate.
Description
Technical Field
The invention relates to a pulse power supply technology, in particular to an unobstructed electric spark pulse power supply and a machining and gap discharge state identification method thereof.
Background
The pulse power supply is a core part of the electric discharge machine tool, and determines the roughness of a machined surface, the wire electrode loss, the machining precision, the machining efficiency, the utilization rate of electric energy and the like, so that the part machining puts very high requirements on the efficiency and the like of the pulse power supply. In the industrial field of medium-speed wire cutting electric spark, a resistance transistor power supply is adopted as a pulse power supply of a part of commercial machine tools, and the output current is adjusted by adjusting the resistance value of a series resistor of a power loop, but the pulse power supply has high loss and low efficiency.
In addition, the gap discharge state of the power supply is the only basis for servo tracking of the machine tool, and the gap discharge state of the pulse power supply can be accurately identified, so that the machining efficiency and the discharge rate can be improved. The traditional gap discharge state identification is carried out according to the filtered gap average voltage, the detection time is in the millisecond level, each machining cycle is generally in the microsecond level, and therefore the gap discharge condition of each machining cycle cannot be known by adopting the traditional method, and harmful pulses (such as transient short circuit caused by poor chip removal) are processed in time. Secondly, during actual machining, the pulse width to pulse ratio is adjusted accordingly according to different machining requirements, so that the relative magnitude of the average voltage threshold of the three gap discharge states is also changed, and therefore, the gap average voltage state identification method is not applicable.
Disclosure of Invention
The invention aims to provide a method for identifying the gap discharge state of a resistance-free medium-speed wire-moving pulse power supply.
The technical solution for realizing the purpose of the invention is as follows: a non-resistance type middle-speed wire-moving pulse power supply comprises a power loop, a driving circuit, an FPGA controller, a voltage detection circuit and a current detection circuit, wherein the power loop is used for providing breakdown voltage and discharge energy after breakdown for a gap; the voltage detection circuit and the current detection circuit are used for detecting voltage and current signals of the gap in real time, filtering and conditioning the voltage and current signals to obtain analog signals, and performing analog-to-digital conversion to obtain digital signals to the FPGA controller; the FPGA controller is used for outputting PWM control signals to the driving circuit according to the current, the voltage and given target parameters, analyzing the current and voltage signals, identifying the gap discharge state of each machining period and providing a basis for the feeding direction and speed of the servo system; the driving circuit carries out digital isolation and amplification on the PWM control signal to generate a driving signal to drive the on-off of the MOS tube in the power loop.
The power loop adopts a step-down synchronous rectification Buck type circuit without an output capacitor as a main topology and comprises an input voltage-stabilizing electrolytic capacitor, a first switch tube, a second switch tube, an inductor and a diode, wherein one end of the first switch tube is connected with one end of the second switch tube, the other ends of the first switch tube and the second switch tube are respectively connected with two ends of the input voltage-stabilizing electrolytic capacitor, a connection point of the first switch tube and the second switch tube is connected with the inductor, the other end of the inductor is connected with the anode of the diode, and the cathode of the diode and the connection point of the second switch tube and the input voltage-stabilizing electrolytic capacitor are respectively connected with two ends of a gap.
The first switch tube and the second switch tube are N-channel MOSFETs of the model number IPP200N25NFD of infineon company, the inductor adopts a power flat wire inductor, and the diode is of the model number SBR60A300 CT.
The FPGA controller is selected to be EP4CE15F23C 8.
The drive circuit adopts a structure that a digital isolator and a non-isolated half-bridge drive chip are added, the digital isolator adopts a chip with the model of ADUM1100, the half-bridge drive chip adopts a drive chip with the model of UCC27714, the ADUM1100 receives a PWM output signal of FPGA, then the isolated signal is output to the primary side of the UCC27714, amplified by the drive chip and then driven to an MOS tube in a power loop.
The voltage detection circuit adopts an operational amplifier circuit for instruments.
The current detection circuit comprises a Hall current sensor and an operational amplifier to form a post-stage conditioning circuit.
A processing method based on a non-resistance type middle-speed wire-moving pulse power supply comprises the following steps:
step 1: in an arc striking stage, namely when one processing cycle begins, a PWM signal is generated by the FPGA controller, and after the PWM signal is amplified by a driving circuit, the first switching tube is controlled to be conducted, the second switching tube is controlled to be switched off, and input voltage is provided for a load gap;
step 2: if the current detection circuit detects that the current rises and the voltage detection circuit detects that the voltage drops within a set maximum breakdown waiting time threshold, the gap is broken down or short-circuited, the first switching tube is continuously conducted during gap discharge until the current reaches an expected value or abnormal discharge is detected, the FPGA controls to generate a PWM signal to control the first switching tube to be disconnected, the second switching tube is controlled to be connected after dead time, the current flows for inductance current, and the gap cut-off stage is started when the current reaches zero, and the second switching tube is disconnected at the moment;
if the current detection circuit and the voltage detection circuit still do not detect clearance breakdown after the first switch tube is conducted for setting the maximum breakdown waiting time threshold value, the machining cycle does not discharge, and the first switch tube waits for entering the next machining cycle;
and step 3: and repeating the two steps to realize the cycle of the processing period.
A clearance discharge state identification method based on a non-resistance type middle-wire-moving pulse power supply comprises the following steps:
step 1: at the beginning of a processing cycle, i.e. from the first switching tubeQ 1) When the current is conducted to a set maximum waiting breakdown time threshold, detecting the gap voltage in the time period to calculate an average voltage, and if the average voltage is a no-load voltage, identifying that the gap is in a no-load state; otherwise, go to step 2Judging normal discharge and short circuit discharge;
step 2: when the first switch tube (Q 1) After the disconnection and dead time, the second switch tube (Q 2) When the current is conducted, detecting the gap current to calculate the change rate of the descending slope of the current, if the change rate of the slope exceeds a set descending slope change rate threshold value, identifying the gap as a short circuit, and if the slope is almost unchanged or slightly changed, identifying the gap as normal discharge;
and step 3: and (3) repeating the steps 1 and 2, and identifying the gap discharge state in each machining period.
Compared with the prior art, the invention has the following remarkable advantages: 1) the pulse power supply has the advantages of simple structure, energy storage by inductance, high efficiency, energy saving, no need of high-voltage breakdown loop and flexible and reliable control; 2) the power topology adopts a step-down synchronous rectification Buck type circuit without an output capacitor, and a diode is connected in series at the output side of an inductor, so that the current reverse flow caused by gap voltage oscillation can be prevented; 3) the voltage detection adopts the operational amplifier circuit, and the current detection adopts the Hall current sensor and the conditioning circuit, so that the stability, the accuracy, the high bandwidth and the real-time performance of the voltage and current measurement are ensured, and the real-time identification of the discharge state in a single subsequent processing period is ensured; 4) the identification method integrates the real-time voltage and current of the gap, the accuracy of the identification of the discharge state is not influenced by the discharge pulse width, the time ratio between pulses and the processing period, and various processing parameters can be adjusted at will.
Drawings
FIG. 1 is a block diagram of a system architecture of a non-resistive type middle-speed wire-moving pulse power supply according to the present invention.
FIG. 2 is a circuit diagram of a power circuit of the non-resistance type middle-speed wire-moving pulse power supply of the present invention.
FIG. 3 is a schematic diagram of the digital isolator and the driving chip used in the present invention.
Fig. 4 is a differential voltage sampling circuit diagram.
Fig. 5 is a hall current sensor application diagram.
Fig. 6 is a schematic diagram of the discharge waveform of a single processing cycle in medium-speed wire processing.
FIG. 7 is a voltage-current diagram of three gap discharge states.
FIG. 8 is a waveform diagram of the gap voltage and current test in three states of no-load, normal discharge and short circuit.
FIG. 9 is a waveform diagram of the gap voltage and current experiment of the continuous machining discharge at different pulse width to pulse ratios according to the present invention.
Detailed Description
The invention is further illustrated by the following examples in conjunction with the accompanying drawings.
As shown in fig. 1, the resistance-free medium-speed wire-moving pulse power supply comprises a power loop, a driving circuit, a field programmable gate array FPGA controller, a voltage detection circuit and a current detection circuit. The power loop is responsible for providing breakdown voltage and discharge energy after breakdown for the gap; the voltage detection circuit and the current detection circuit detect the voltage and the current of a load (gap) in real time, the signals are filtered and conditioned to obtain analog signals, the analog signals are subjected to analog-to-digital conversion to obtain digital signals, and the digital signals are finally sent to the FPGA controller; the FPGA controller outputs a PWM control signal to the drive circuit according to the obtained current and voltage detection signals and the given target parameters, and the drive circuit carries out digital isolation and amplification on the PWM control signal to generate a drive signal to drive the on-off of the MOS tube in the power loop. Meanwhile, the detected voltage and current signals are analyzed and calculated by the FPGA controller to identify the gap discharge state of each machining period in real time, and the FPGA outputs signals of corresponding states to servo tracking so as to provide necessary basis for the feeding direction and the feeding speed of a servo system.
As shown in figure 2, the power loop adopts a step-down synchronous rectification Buck type circuit without an output capacitor as a main topology and comprises an input voltage-stabilizing electrolytic capacitorC in2 switch tubesQ 1、Q 21 inductorL 1And a diodeD out。Q 1AndQ 2respectively as upper and lower tubes, andL 1so as to form a synchronous rectification topology,L 1at the other end ofD outThe anode of (a) is provided,D outcathode and lowerPipeQ 2The other end of which terminates at both ends of the gap. Because a diode is connected in series on the output side of the inductor, the reverse current of the current caused by gap voltage oscillation can be prevented.
The switch tube in the power loop adopts a power MOS tube made of SiC material, and a metal-oxide semiconductor field effect transistor (MOSFET) is selected. The N-channel MOSFET with the model number of IPP200N25NFD manufactured by infineon company is selected according to the requirement of an actual quick wire cut electrical discharge machining pulse power supply, and the drain-source voltage resistance of the N-channel MOSFET isV DSUp to 250V, rated currentI DThe on-state internal resistance is 61A, the on-state internal resistance is less than 22 milliohms, the maximum allowable pulse current is 256A, the working frequency is up to 1MHz, and the wire cutting device can be used for high-frequency, large-current, medium-low-power and fast-moving wire cutting. The inductor adopts a power flat wire inductor, the inductance value is 3.3uH, the diode adopts the model of SBR60A300CT, the reverse voltage resistance is 300V, and the forward continuous conduction current is 60A.
And signals for controlling the on-off of the MOS tube in the power loop are generated by the FPGA controller. The FPGA selects the model number EP4CE15F23C8 as a high-speed processor of the cycle IV series of Altera company, the clock frequency of the high-speed processor reaches 472MHz, and two paths of high-speed and high-precision AD conversion chips are arranged for inputting sampling signals.
Considering that the FPGA is not enough to drive the on-off of the switch tube and the mutual influence between the power circuit and the weak current circuit, an isolated driving circuit is needed between the FPGA and the power circuit and is used for amplifying a control signal sent by the FPGA and outputting a driving signal with a certain voltage amplitude value meeting the driving capability.
As shown in fig. 3, the isolated driving circuit is formed by a digital isolator and a non-isolated half-bridge driving chip. The digital isolator adopts a chip with the model number of ADUM1100, receives a PWM output signal of the FPGA, outputs an isolated signal to the primary side of a drive chip UCC27714, amplifies the isolated signal by the drive chip, and then drives an MOS tube in a power loop. UCC27714 can be configured with high and low sides with independent inputs, HS pin voltage up to 600V when fully operating, sink/source current of 4A, dedicated to driving power Metal Oxide Semiconductor Field Effect Transistors (MOSFETs), or insulated gate bipolar transistors.
No matter the control of the power loop, the protection function and the equal energy discharge are realized, or the gap discharge real-time state is provided for the servo tracking system in order to improve the discharge rate, and the real-time and accurate voltage and current detection is needed. As shown in fig. 4, the voltage detection circuit adopts an operational amplifier circuit (differential voltage sampling) for the instrument, and has the advantages of high input impedance, high common mode rejection ratio, convenient gain adjustment, high bandwidth, accurate sampling and the like; as shown in fig. 5, the current detection circuit adopts a hall current sensor and an operational amplifier to form a subsequent conditioning circuit, and has the advantages of isolation, safety, reliability, high precision and the like. Both the high-speed and wide-bandwidth operational amplifier chips LMH6643MAX/NOPB are adopted, and the high-speed and wide-bandwidth operational amplifier chips are strong in interference resistance, high in accuracy and good in stability. The current Hall sensor adopts a current chip of Allegro company with the model of ACS732, the output bandwidth can reach 1MHz, the measuring range is 40A, and the detection requirement of the pulse power supply is met.
In summary, the power topology of the resistance-free medium-speed wire-passing pulse power supply adopts a step-down synchronous rectification Buck type circuit without an output capacitor, and a diode is connected in series on the output side of the inductor, so that the occurrence of reverse current caused by gap voltage oscillation can be prevented. The pulse power supply has the advantages of simple structure, energy storage by an inductor, no resistance, high efficiency, energy saving, no need of a high-voltage breakdown loop and flexible and reliable control.
As shown in fig. 5, a complete machining cycle, including a machining phase and a deionization phase, the machining phase including an arc striking phase and a discharge phase,t din order to carry out the arc striking stage,t onin order to be in the discharge phase,t offfor the deionization phase, the three phases are added up to form a complete processing cycleT s. Here, for example, when the equal energy triangular wave machining is performed, at the beginning of one machining cycle, that is, at the beginning of one machining cyclet 0At the moment of time, the time of day,Q 1the switching-on is equivalent to the full duty cycle of a synchronous rectification Buck type power circuit, a higher breakdown voltage (also called no-load voltage) is generated at two ends of a gap of an output end, the magnitude of the breakdown voltage is input voltage, the breakdown discharge can be conveniently realized when the control gap of a servo system is close enough, and the maximum equal-duty cycle is setTime to breakdownt dm(i.e. thet dMaximum value of) ift dIs greater thant dmWhen the gap voltage is not detected to drop, and the current is increased, the breakdown is not considered to be generated, and the direct switch-off is carried outQ 1Without discharging (t onZero), enter the deionization phase.
If when it is usedt dIs less than or equal tot dmWhen the gap breakdown is detected, the discharge stage is started, and the current detection circuit is disconnected when the gap current reaches a preset target valueQ 1After a dead zone of 100ns, it is turned on againQ 2Providing a free-wheeling circuit, starting the current drop, and turning off when the current drops to 0Q 2And ending the discharging phase, starting to enter the deionization phase and continuing until the next processing period.
If the gap is in a short circuit condition, there is no arc strike stage: (t d) As long asQ 1Once the current is on, the current begins to rise and then reaches the target value, and the current is cut offQ 1After dead timeQ 2The current drops to 0, is turned offQ 2Until the end of this processing cycle.
In summary, the method for controlling the processing of the non-resistance type medium-speed wire-moving pulse power supply comprises the following steps:
step 1: in an arc striking stage (the gap is not broken down), when one processing period begins, the FPGA generates a PWM signal, and the PWM signal is amplified by a driving circuit and then controlledQ 1The power-on state is carried out,Q 2and is turned off to provide a relatively high breakdown voltage to the load gap, equal to the input voltage, to enable breakdown discharge when the gap distance is relatively close. If when it is usedQ 15us on (a set maximum waiting breakdown time threshold, i.e. during which time high voltage is provided to the gap), no gap breakdown is detected by current voltage detection, the machining cycle is not discharged and disconnectedQ 1. Waiting for the next processing cycle to be entered.
Step 2: if when it is usedQ 1When the on-time is less than 5us, the current is detectedWhen the voltage rises and drops, the gap breaks down (or short-circuits) and enters the gap discharge period,Q 1continuing to turn on (without the limit of 5us time threshold) until the current reaches the desired value (or abnormal discharge such as short circuit) is detected, generating PWM signal by FPGA, and controllingQ 1Disconnected, and controlled after dead time of 100nsQ 2And turning on to obtain inductor current follow current. When the current reaches zero, the gap cut-off phase (inter-pulse) is entered, and the switch-off is carried outQ 2。
And step 3: and repeating the two steps to realize the cycle of the processing period.
Fig. 6 is a schematic diagram of the gap voltage current waveform for three process cycles, including three gap discharge states, i.e., no load, normal discharge, and short circuit. It can be seen that, at no load, the gap voltage is very high, which is the input voltage, and there is very little leakage current; for the normal discharge state, when a machining cycle begins, the gap output voltage is no-load voltage and lasts for a period of time, when the gap breaks down, the gap voltage rapidly drops to the maintaining voltage, and then the gap current also rapidly rises; when the gap is short-circuited, the gap voltage drops very low at the beginning of a machining, the current rises rapidly, and the slope change is relatively large in the current drop phase. Accordingly, the invention also provides a novel gap discharge state monitoring method by detecting the time from the moment of supplying high voltage to the latert dmThe method comprises the following steps of (maximum breakdown waiting time) judging the gap discharge state by the average voltage of the gap in the time and the slope change of the current reduction stage, and specifically comprises the following steps:
step 1: the voltage detection circuit and the current detection circuit measure the real-time voltage and current waveform of the gap, the real-time voltage and current waveform is transmitted to the FPGA module after AD conversion, and after software filtering, a processing cycle is started, namely from the beginningQ 1The voltage waveform from the time of turn-on to the next 5us (the set maximum waiting breakdown time threshold) is measured, and the average voltage is calculatedV avgThe average voltages of no-load, normal discharge and short circuit states are recorded asV avg1、V avg2、V avg3；
The actual gap voltage and current waveform diagrams of the gap in three states of no load, normal discharge and short circuit are shown in fig. 8 by experiments on the medium-speed wire-cut electric discharge machine, and the following conclusion is reached: when the device is in the idle state,V avg1the magnitude is equal to the no-load voltage; during the normal discharge, the discharge is carried out,V avg2between the no-load voltage and the sustain voltage; when the short circuit is generated,V avg3a magnitude equal to the short circuit voltage; the no-load voltage is equal to the maximum output voltage of the pulse power supply, generally 80V is selected, the maintaining voltage is generally 20V and slightly larger than the short-circuit voltage, the short-circuit voltage is generally below 10V, and the short-circuit voltage can be seenV avg1Far greater thanV avg2，V avg2Slightly larger thanV avg3. However, if the servo tracking is relatively tight in actual machining and the pulse power supply discharges continuously, the breakdown waiting time during normal discharge is almost zero, and the breakdown waiting time is at this timeV avgApproaches the short-circuit voltage, so that the no-load state can be identified according to the average voltage, and the normal discharge and short-circuit state cannot be completely identified according to the average voltage, namely when the calculated average voltageV avgAnd (3) when the voltage is in the no-load voltage state, identifying the gap in the no-load state, and otherwise, turning to the step 2 to further judge whether the discharge is in the normal discharge state or the short-circuit state.
Step 2: when in useQ 1Disconnect, wait for dead time (typically taken to be 100 ns),Q 2when the current is switched on, the current begins to drop, a real-time waveform of a current dropping stage is obtained through current sampling, the change of a current dropping slope is calculated, if the change of the slope is large and exceeds a set dropping slope threshold value, the gap is identified as a short circuit, and if the slope is almost unchanged or the change is small, the gap is identified as normal discharge.
And step 3: and finishing the gap discharge state identification of one machining cycle. And (3) repeating the steps 1 and 2, and identifying the gap discharge state of each machining period, so that important indexes of the feeding direction and the feeding speed are provided for servo tracking. The gap discharge state detection method is utilized to carry out servo tracking to obtain the continuous discharge waveform shown in figure 9, and the method can indirectly prove that the novel identification method provided by the invention has the advantages that the critical output average voltage threshold of three discharge states is determined, the method is not limited by the discharge pulse width, the time ratio between pulses and the processing period, and various processing parameters can be adjusted at will.
Claims (8)
1. The nonresistance type medium-speed wire-moving pulse power supply is characterized by comprising a power loop, a driving circuit, an FPGA controller, a voltage detection circuit and a current detection circuit, wherein the power loop is used for providing breakdown voltage and discharge energy after breakdown for a gap; the voltage detection circuit and the current detection circuit are used for detecting voltage and current signals of the gap in real time, filtering and conditioning the voltage and current signals to obtain analog signals, and performing analog-to-digital conversion to obtain digital signals to the FPGA controller; the FPGA controller is used for outputting PWM control signals to the driving circuit according to the current, the voltage and given target parameters, analyzing the current and voltage signals, identifying the gap discharge state of each machining period and providing a basis for the feeding direction and speed of the servo system; the driving circuit carries out digital isolation and amplification on the PWM control signal to generate a driving signal to drive the on-off of an MOS (metal oxide semiconductor) tube in the power loop;
the power loop adopts a step-down synchronous rectification Buck type circuit without an output capacitor as a main topology and comprises an input voltage-stabilizing electrolytic capacitor (C)in) First switch tube (Q)1) A second switch tube (Q)2) Inductance (L)1) And a diode (D)out) Wherein the first switch tube (Q)1) And a second switching tube (Q)2) One end connected to the first switch tube (Q)1) And a second switching tube (Q)2) The other end is respectively connected with an input voltage stabilizing electrolytic capacitor (C)in) Are connected with each other, a first switching tube (Q)1) And a second switching tube (Q)2) Connection point and inductance (L)1) Connection, inductance (L)1) Is connected with a diode (D)out) Anode of (D), diode (D)out) And a second switching tube (Q)2) And an input voltage-stabilizing electrolytic capacitor (C)in) The connection points of (a) are respectively connected with the two ends of the gap.
2. According to the rightThe resistless type middle-speed wire-moving pulse power supply of claim 1, characterized in that the first switch tube (Q)1) And a second switching tube (Q)2) An N-channel MOSFET of the type IPP200N25NFD manufactured by infineon corporation is selected, and the inductor (L)1) The power flat conductor inductor is adopted, and the model of the diode is SBR60A300 CT.
3. The resistless type mid-travel pulsed power supply of claim 1, wherein the FPGA controller is selected to be model EP4CE15F23C 8.
4. The resistless type middle-speed wire-moving pulse power supply as claimed in claim 1, wherein the driving circuit adopts a structure of a digital isolator and a non-isolated half-bridge driving chip, the digital isolator adopts a chip with a model of ADUM1100, the half-bridge driving chip adopts a driving chip with a model of UCC27714, the ADUM1100 receives a PWM output signal of the FPGA, then outputs the isolated signal to a primary side of the UCC27714, and the isolated signal is amplified by the driving chip and then drives an MOS tube in the power loop.
5. The resistless type middle-speed wire-moving pulse power supply as claimed in claim 1, wherein the voltage detection circuit employs an operational amplifier circuit for instruments.
6. The resistless type middle-speed wire-moving pulse power supply as claimed in claim 1, wherein the current detection circuit comprises a Hall current sensor and an operational amplifier to form a subsequent stage of conditioning circuit.
7. The method for processing the resistless type middle-speed wire-moving pulse power supply according to any one of claims 1 to 6, characterized by comprising the following steps:
step 1: in the arc striking stage, namely when one processing period starts, the FPGA controller generates a PWM signal, and the PWM signal is amplified by a driving circuit to control a first switching tube (Q)1) Conducting, second switch tube (Q)2) Turning off, providing an input voltage to the load gap;
step 2: if the current detection circuit detects the current rise and the voltage detection circuit detects the voltage drop within the set maximum waiting breakdown time threshold value, the gap is broken down or short-circuited, and the first switch tube (Q) enters a gap discharge period1) Continuing to conduct until the current reaches the expected value or abnormal discharge is detected, generating a PWM signal by FPGA control, and controlling a first switch tube (Q)1) After the dead time, the second switch tube (Q) is controlled2) Turning on to make the current of inductor follow current, when the current reaches zero, entering the gap cut-off stage, at the same time turning off the second switch tube (Q)2)；
If the first switch tube (Q)1) After the set maximum waiting breakdown time threshold value is switched on, the current detection circuit and the voltage detection circuit still do not detect clearance breakdown, the machining period does not discharge, and the first switch tube (Q)1) Waiting for entering the next processing period;
and step 3: and repeating the two steps to realize the cycle of the processing period.
8. The clearance discharge state identification method of the resistless type middle-speed wire-moving pulse power supply according to any one of claims 1 to 6, characterized by comprising the following steps:
step 1: at the beginning of a machining cycle, i.e. from the first switching tube (Q)1) When the current is conducted to a set maximum waiting breakdown time threshold, detecting the gap voltage in the time period to calculate an average voltage, and if the average voltage is a no-load voltage, identifying that the gap is in a no-load state; otherwise, turning to the step 2 to judge normal discharge and short-circuit discharge;
step 2: when the first switch tube (Q)1) Off and after dead time, the second switching tube (Q)2) When the current is conducted, detecting the change of a descending slope of the current by the gap current, if the change of the slope exceeds a descending slope change rate threshold value, identifying the gap as a short circuit, and if the slope is almost unchanged or the change is small, identifying the gap as normal discharge;
and step 3: and (3) repeating the steps 1 and 2, and identifying the gap discharge state in each machining period.
Priority Applications (1)
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| CN112404615A (en) * | 2020-11-09 | 2021-02-26 | 宁波工程学院 | Electric spark machine tool capable of converting modules |
| CN113271030B (en) * | 2021-05-25 | 2022-11-29 | 中国工程物理研究院机械制造工艺研究所 | Pulse generation control method for pulse power supply |
| CN114888373B (en) * | 2022-06-01 | 2023-09-29 | 南京理工大学 | Three-level BUCK pulse power supply for electric spark machining |
| CN115070142B (en) * | 2022-06-01 | 2023-09-05 | 南京理工大学 | Novel peak current control method applied to electric spark machining pulse power supply |
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| CN107186295B (en) * | 2017-05-27 | 2019-10-18 | 南京理工大学 | A kind of energy control methods such as the constant frequency of the fine electric spark pulse power |
| CN107276405B (en) * | 2017-05-27 | 2019-06-04 | 南京理工大学 | The fine electric spark pulse power and Discrete control method based on the power supply |
| CN107398612A (en) * | 2017-09-13 | 2017-11-28 | 厦门大学 | A kind of electric spark clearance discharge condition detection apparatus and method based on cluster analysis |
| CN108380988B (en) * | 2018-01-30 | 2019-06-21 | 南京理工大学 | A kind of WEDM pulse power supply and its control method |
| CN108672858B (en) * | 2018-06-30 | 2020-05-22 | 南京理工大学 | Full-bridge staggered parallel bipolar wire cut electrical discharge machining pulse power supply and machining method |
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