A micro-energy pulse method with real-time controllable discharge pulse energy

Abstract

The present invention discloses a micro-energy pulse method with real-time controllable discharge pulse energy, comprising: S1: determining the pulse basic parameters of the pulse power supply according to the workpiece processing requirements, and determining the working path of the capacitor group and the movement displacement of the stepper motor; S2: the controller outputs a control pulse signal to the pulse power supply main circuit to control the on-off moment of the switch tube according to the determined pulse basic parameters; S3: when there is a special processing requirement of real-time variable pulse energy, the controller outputs a capacitor group path control signal according to the determined capacitor group path; at the same time, the controller outputs a stepper motor control signal to the motor driver to drive the stepper motor to rotate a specified angle to change the discharge resistor value, thereby realizing real-time adjustment of the pulse energy. The present invention realizes real-time controllable pulse energy of machine tools during processing, greatly expanding the range of machinable parts of the equipment.

Description

Technical Field

[0001] The present invention specifically relates to pulse energy, and in particular to a micro-energy pulse method with real-time controllable discharge pulse energy. Background Art

[0002] EDM technology is widely used in many fields such as aviation, aerospace, automobile manufacturing, military industry, and mold industry due to its advantages such as being able to use soft tools to process hard workpieces, small cutting force during the machining process, which will not cause deformation of the workpiece, and the machining accuracy is directly related to the pulse energy, making it easy to control the machining accuracy.

[0003] As the key technology of EDM equipment, pulse power supply directly affects the quality of machining process. With the development and application of new science and technology, the industrial field has more and more extensive requirements for the shape of parts. The development of pulse power supply has mainly experienced RC relaxation type, thyristor type, transistor type and various derivative pulse power supplies, and its functions are gradually enriched. However, in the existing pulse power supply technology, the control of pulse energy is set before the start of machining. The machining parameters and discharge energy cannot be adjusted during the machining process after the start of machining, which seriously restricts the diversity of parts to be processed.

[0004] The single pulse energy of RC pulse power supply can be miniaturized to meet the requirements of micro-energy processing, so RC pulse power supply is well used in micro-energy processing, but the traditional RC pulse power supply has the problem that the pulse energy cannot be controlled in real time. The core technology of the present invention is that it can realize the real-time change of pulse energy during the processing process, and can process parts that cannot be processed by existing technology. Summary of the invention

[0005] The purpose of the present invention is to provide a micro-energy pulse method with real-time controllable discharge pulse energy, which can effectively solve the above-mentioned technical problems.

[0006] In order to achieve the purpose of the present invention, the following technical scheme is adopted: a micro-energy pulse method with real-time controllable discharge pulse energy, comprising:

[0007] S1: According to the workpiece processing requirements, determine the pulse basic parameters of the pulse power supply, and determine the working path of the capacitor group and the movement displacement of the stepper motor;

[0008] S2: The controller outputs a control pulse signal to the pulse power supply main circuit to control the on-off moment of the switch tube according to the determined pulse basic parameters;

[0009] S3: When there are special processing requirements for real-time variable pulse energy, the controller outputs a capacitor group path control signal according to the determined capacitor group path; at the same time, the controller outputs a stepper motor control signal to the motor driver to drive the stepper motor to rotate a specified angle to change the resistance value, thereby realizing real-time adjustment of the pulse energy.

[0010] Preferably, the basic pulse parameters include: peak current, capacitance value, pulse width and pulse interval;

[0011] Among them, generally before processing parts, it is necessary to provide part processing requirements, such as part material, surface roughness Ra requirements, and processing size cross-section. The above basic pulse parameters can be determined based on the processing requirements.

[0012] Preferably, the controller outputs a control pulse signal to the pulse power supply main circuit. In one control pulse cycle, the pulse signal of the controller is isolated by the high-speed optical coupler U6 and is divided into two paths. One signal is transmitted to the voltage comparator U1A and compared with the voltage value set in the circuit.

[0013] Another signal is transmitted to the non-inverting terminal of the voltage comparator U3A. When the input signal is at a high level, the non-inverting input terminal of the voltage comparator U5A is higher than the inverting input terminal, and a high level is output. After passing through the single-channel MOSFET gate driver circuit U7A, the high level signal drives the field effect transistor Q2 to turn on, and the capacitor C10 discharges to the machining gap through the variable resistor R14.

[0014] Preferably, the set reference voltage at the inverting input terminal of the comparator U5A is isolated by the control pulse output by the controller through the optocoupler U7, and then input into the voltage follower circuit composed of U4A, and then input into the filter circuit composed of resistor R30 and capacitor C20 to convert the pulse voltage into a DC voltage with a certain fluctuation, and finally input into the follower circuit composed of U6A, resistor R31, and capacitor C21 for filtering, and converts the previous stage input into a DC voltage with very small fluctuation. The DC voltage is the set voltage comparison value, which is linearly related to the duty cycle of the controller input pulse signal. Different reference voltage outputs are achieved by adjusting the duty cycle of the control pulse.

[0015] Preferably, when the input signal is at a high level, the non-inverting terminal of the voltage comparator U1A is lower than the inverting terminal, and the voltage comparator U1A outputs a low level;

[0016] On the contrary, when the input signal is at a low level, the in-phase segment of the voltage comparator U1A is higher than the inverting terminal, and the voltage comparator U1A outputs a high level, generating a rising edge signal acting on the CP1 pin of the trigger U2A, so that the Q1 pin of the trigger U2A becomes a high level. The high level signal drives the field effect transistor Q1 to turn on after passing through the single-channel MOSFET gate driver circuit U3;

[0017] The capacitor C10 is charged by the power supply VCC0 and the charging current limiting resistor R8. The two ends of the capacitor C10 are connected in parallel with the voltage dividing resistors R9 and R10. The voltage dividing signal at both ends of the capacitor is transmitted to the voltage comparator U5A and compared with the set voltage value.

[0018] After the field effect transistor Q1 (IRF730) is turned on and charged, the voltage across the capacitor C10 rises. When the voltage across the capacitor C10 exceeds the set comparison value, that is, the upper limit of the charging voltage, the non-inverting input terminal of the voltage comparator U5A is higher than the inverting input terminal, and the output is high level;

[0019] The high level is transmitted to the reset pin CD1 of the trigger U2A, and the Q1 pin of the trigger U2A outputs a low level. The low level signal drives the field effect transistor Q1 to turn off after passing through the single-channel MOSFET gate driver circuit U3, thereby controlling the upper limit of the charging voltage of the capacitor C10 to the set value.

[0020] Preferably, the controller determines the capacitance value of the discharge circuit according to the special processing requirements of the real-time variable pulse energy of the processed parts, outputs the capacitance group path control signal to the capacitance group circuit, and controls the path of the working capacitances C10 to C1n of the capacitance group circuit;

[0021] Since the paths of capacitors C10 to C1n correspond to capacitors of different values, it is possible to obtain discharge circuit capacitors of different sizes;

[0022] At the same time, the controller outputs the displacement and direction control pulse signal of the stepper motor 57CM23 according to the determined variable resistance value;

[0023] The stepper motor displacement pulse control signal output by the controller to the stepper motor driver M542C is input from the PUL pin;

[0024] The stepper motor direction control pulse control signal output by the controller to the stepper motor driver M542C is input from the DIR pin;

[0025] The stepper motor enable signal output by the controller to the stepper motor driver M542C is input from the ENA pin;

[0026] The stepper motor 57CM23 rotates a specified angle under the control of the displacement, direction, and enable signals input by the controller to the stepper motor driver M542C, thereby controlling the rotary variable resistor to a specified value.

[0027] Preferably, the displacement signal is a periodic electric pulse signal output by the controller STM32F103, and the controller STM32F103 is connected to the stepper motor driver M542C through a lead. The periodic electric pulse signal is transmitted to the displacement interface of the stepper motor driver M542C through the lead, and after being processed by the stepper motor controller M542C, it drives the stepper motor 57CM23 to rotate.

[0028] Preferably, the variable pulse energy requirement refers to the change of the processing cross-sectional area during the processing. Usually, different materials correspond to different unit area current density values. The product of the unit area current density value and the cross-sectional area can determine the peak current of different cross-sections. The discharge energy that can be stored on the capacitor can be expressed as:

[0029]

[0030] Where Vs refers to the charging voltage of capacitor C, so the pulse energy is proportional to the capacitance value;

[0031] Another way to express the discharge energy is:

[0032]

[0033] u(t), i(t) refer to the discharge voltage and discharge current respectively. The discharge time T is the maximum pulse width. The discharge energy is related to the discharge voltage, discharge current and discharge time.

[0034] In actual discharge, the discharge voltage is basically constant, so the peak current in the set pulse width range determines the maximum discharge energy;

[0035] The maximum discharge energy is equal to the energy stored in the capacitor, so the above two discharge energy formulas are equal. In this way, the required capacitance value can be calculated based on the previously determined discharge peak current.

[0036] Determination of the value of variable resistor R2:

[0037] Changing the value of R2 can change the discharge current as follows:

[0038]

[0039] The discharge current can change the machining size (radius of the discharge cross-sectional area) through the discharge energy and the discharge gap, so R2 has a corresponding relationship with the target discharge machining size.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) The machine tool discharge pulse energy can be controlled in real time during the machining process, greatly expanding the range of parts that can be machined by the equipment.

[0042] (2) At the same time, the discharge energy is adjusted in real time according to the special processing requirements of different parts to complete the processing of parts, thereby enhancing the flexibility of pulse power supply application. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for describing the embodiments are briefly introduced below.

[0044] Figure 1 This is a pulse power supply working flow chart in an embodiment of the present invention;

[0045] Figure 2 This is a main circuit diagram of a pulse power supply in an embodiment of the present invention;

[0046] Figure 3 Schematic diagram of stepper motor drive control in an embodiment of the present invention. DETAILED DESCRIPTION

[0047] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0048] like Figures 1 to 3 As shown, a micro-energy pulse method with real-time controllable discharge pulse energy comprises:

[0049] S1: According to the workpiece processing requirements, determine the pulse basic parameters of the pulse power supply, and determine the working path of the capacitor group and the movement displacement of the stepper motor;

[0050] Among them, the basic pulse parameters include: peak current, capacitance value, pulse width and pulse interval;

[0051] Among them, generally before processing parts, it is necessary to provide part processing requirements, such as part material, surface roughness Ra requirements, and processing size cross-section. The above basic pulse parameters can be determined based on the processing requirements.

[0052] Usually, different materials are subject to Ra constraints and correspond to different empirical current density values ​​per unit area. The product of the empirical current density value per unit area and the cross-sectional area is the peak current of different cross-sections.

[0053] S2: The controller outputs a control pulse signal to the pulse power supply main circuit to control the on and off timing of the switch tube according to the determined pulse basic parameters.

[0054] The controller outputs a control pulse signal to the pulse power supply main circuit. In one control pulse cycle, the pulse signal of the controller is isolated by the high-speed optocoupler U6 (6N137) and is divided into two paths. One path is transmitted to the voltage comparator U1A (LM311N) and compared with the voltage value set in the circuit.

[0055] Among them, the set reference voltage at the inverting input terminal of the comparator U5A (LM311N) is isolated by the control pulse output by the controller through the optocoupler U7 (tlp521) and then input into the voltage follower circuit composed of U4A (AD8065).

[0056] It is then input into a filter circuit composed of a resistor R30 and a capacitor C20 to convert the pulse voltage into a DC voltage with a certain fluctuation. Finally, it is input into a follower circuit composed of U6A (AD8065), a resistor R31, and a capacitor C21 for filtering, converting the previous stage input into a DC voltage with very small fluctuations. This DC voltage is the set voltage comparison value.

[0057] This value is linearly related to the duty cycle of the controller input pulse signal. Different reference voltage outputs can be achieved by adjusting the duty cycle of the control pulse.

[0058] Among them, when the input signal is high level, the non-inverting end of the voltage comparator U1A (LM311N) is lower than the inverting end, and the voltage comparator U1A (LM311N) outputs a low level;

[0059] On the contrary, when the input signal is at a low level, the in-phase segment of the voltage comparator U1A (LM311N) is higher than the inverting end, and the voltage comparator U1A (LM311N) outputs a high level, generating a rising edge signal acting on the CP1 pin of the trigger U2A (4013).

[0060] This causes the Q1 pin of the trigger U2A (4013) to become a high level. The high level signal passes through the single-channel MOSFET gate driver circuit U3 (IR2117PBF) and then drives the field effect transistor Q1 (IRF730) to turn on.

[0061] The capacitor C10 is charged by the power supply VCC0 and the charging current limiting resistor R8. The two ends of the capacitor C10 are connected in parallel with the voltage dividing resistors R9 and R10. The voltage divided signal across the capacitor is transmitted to the voltage comparator U5A (LM311N) and compared with the set voltage value.

[0062] After the field effect transistor Q1 (IRF730) is turned on for charging, the voltage across the capacitor C10 rises. When the voltage across the capacitor C10 exceeds the set comparison value (i.e., the upper limit of the charging voltage), the non-inverting input terminal of the voltage comparator U5A (LM311N) is higher than the inverting input terminal, and the output is a high level.

[0063] The high level is transmitted to the reset pin CD1 of the trigger U2A (4013), and the Q1 pin of the trigger U2A (4013) outputs a low level. The low level signal drives the field effect transistor Q1 (IRF730) to turn off after passing through the single-channel MOSFET gate driver circuit U3 (IR2117PBF), thereby controlling the upper limit of the charging voltage of the capacitor C10 to the set value.

[0064] The other signal is transmitted to the non-inverting terminal of the voltage comparator U3A (LM311N). When the input signal is at a high level, the non-inverting input terminal of the voltage comparator U5A (LM311N) is higher than the inverting input terminal, and the output is a high level. The high level signal drives the field effect transistor Q2 (IRF730) to turn on after passing through the single-channel MOSFET gate driver circuit U7A (IR2117PBF), and the capacitor C10 discharges to the machining electrode through the variable resistor R14.

[0065] S3: When there are special processing requirements for real-time variable discharge pulse energy, the controller outputs a capacitor group path control signal according to the determined capacitor group path; at the same time, the controller outputs a stepper motor control signal to the motor driver to drive the stepper motor to rotate a specified angle to change the resistance value of the discharge resistor, thereby realizing real-time adjustment of the discharge pulse energy.

[0066] The controller determines the capacitance value of the discharge circuit according to the special processing requirements of the real-time discharge pulse energy of the processed parts, outputs the capacitance group path control signal to the capacitance group circuit, and controls the path of the working capacitances C10 to C1n of the capacitance group circuit;

[0067] Since the paths of capacitors C10 to C1n correspond to capacitors of different values, it is possible to obtain discharge circuit capacitors of different sizes;

[0068] At the same time, the controller outputs the displacement and direction control pulse signal of the stepper motor 57CM23 according to the determined variable resistance value;

[0069] Among them, the variable pulse energy requirement refers to the change of the processing cross-sectional area during the processing. Usually, different materials correspond to different unit area current density values. The product of the unit area current density value and the cross-sectional area can determine the peak current of different cross-sections. The discharge energy that can be stored on the capacitor can be expressed as:

[0070]

[0071] Where Vs refers to the charging voltage of capacitor C, so the pulse energy is proportional to the capacitance value;

[0072] Another way to express the discharge energy is:

[0073]

[0074] u(t), i(t) refer to the discharge voltage and discharge current respectively. The discharge time T is the maximum pulse width. The discharge energy is related to the discharge voltage, discharge current and discharge time.

[0075] In actual discharge, the discharge voltage is basically constant, so the peak current in the set pulse width range determines the maximum discharge energy;

[0076] The maximum discharge energy is equal to the energy stored in the capacitor, so the above two discharge energy formulas are equal. In this way, the required capacitance value can be calculated based on the previously determined discharge peak current.

[0077] Determination of the value of variable resistor R2:

[0078] Changing the value of R2 can change the discharge current as follows:

[0079]

[0080] The discharge current can change the machining size (radius of the discharge cross-sectional area) through the discharge energy and the discharge gap, so R2 has a corresponding relationship with the target discharge machining size.

[0081] Among them, the stepper motor displacement pulse control signal output by the controller to the stepper motor driver M542C is input from the PUL pin;

[0082] The stepper motor direction control pulse control signal output by the controller to the stepper motor driver M542C is input from the DIR pin;

[0083] The stepper motor enable signal output by the controller to the stepper motor driver M542C is input from the ENA pin;

[0084] The stepper motor 57CM23 rotates a specified angle under the control of the displacement, direction, and enable signals input by the controller to the stepper motor driver M542C, thereby controlling the rotary variable resistor to a specified value.

[0085] Among them, the displacement signal is a periodic electric pulse signal output by the controller STM32F103. The controller STM32F103 is connected to the stepper motor driver M542C through a lead. The periodic electric pulse signal is transmitted to the displacement interface of the stepper motor driver M542C through the lead. After being processed by the stepper motor controller M542C, it drives the stepper motor 57CM23 to rotate.

[0086] Among them, the enable signal is the electrical pulse output by the controller STM32F103, which is transmitted to the enable control port of the stepper motor driver M542C through the lead to control the rotation or emergency stop of the stepper motor. It is mainly used to control the stepper motor, prevent overshoot during operation, and ensure the accuracy of stepper motor positioning.

[0087] The direction control signal is the same as the enable control signal, which is an electrical pulse signal output by the controller STM32F103 and transmitted to the driver direction control interface through the lead. During the operation of the pulse power supply, the value of the rotary variable resistance needs to be increased or decreased in real time.

[0088] Therefore, the stepper motor that controls the variable resistor needs to be able to achieve real-time commutation, and the role of the direction control signal is to realize the commutation operation of the stepper motor through the controller.

[0089] Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

Claims

1. A micro-energy pulse method with real-time controllable discharge pulse energy, characterized in that: include: S1: According to the workpiece processing requirements, determine the pulse basic parameters of the pulse power supply, and determine the working path of the capacitor group and the movement displacement of the stepper motor; S2: The controller outputs a control pulse signal to the pulse power supply main circuit according to the determined pulse basic parameters to control the on and off time of the switch tube; S3: When there is a special processing requirement of real-time variable pulse energy, the controller outputs a capacitor group path control signal according to the determined capacitor group path; at the same time, the controller outputs a stepper motor control signal to the motor driver to drive the stepper motor to rotate a specified angle to change the resistance value of the discharge resistor, thereby realizing real-time adjustment of the discharge pulse energy; The basic pulse parameters include: peak current, capacitance, pulse width and pulse interval; Among them, before processing parts, it is necessary to provide part processing requirements, which include part materials, surface roughness Ra requirements, and processing size cross-sections. The above basic pulse parameters can be determined based on the processing requirements; the controller outputs a control pulse signal to the pulse power supply main circuit. In one control pulse cycle, the controller's pulse signal is isolated by the high-speed optical coupler U6 and is divided into two paths. One signal is transmitted to the voltage comparator U1A and compared with the set reference voltage set in the circuit; Another signal is transmitted to the non-inverting end of the voltage comparator U3A. When the input signal is at a high level, the non-inverting input end of the voltage comparator U5A is higher than the inverting input end, and a high level is output. The high level signal drives the field effect transistor Q2 to turn on after passing through the single-channel MOSFET gate driver circuit U7A, and the capacitor C10 discharges to the machining gap through the variable resistor R14; the set reference voltage of the inverting input end of the voltage comparator U5A is isolated by the control pulse output by the controller through the optical coupler U7, and then input to the voltage follower circuit composed of the voltage comparator U4A, and then input to the voltage follower circuit composed of the electric The filter circuit composed of resistor R30 and capacitor C20 converts the pulse voltage into a DC voltage with certain fluctuations, and finally inputs it into the follower circuit composed of voltage comparator U6A, resistor R31, and capacitor C21 for filtering, converting the previous stage input into a DC voltage with very small fluctuations. The DC voltage is the set voltage comparison value, which is linearly related to the duty cycle of the controller input pulse signal. Different reference voltage outputs are achieved by adjusting the duty cycle of the control pulse; when the input signal is high level, the in-phase end of the voltage comparator U1A is lower than the inverting end, and the voltage comparator U1A outputs a low level; On the contrary, when the input signal is low level, the non-inverting terminal of the voltage comparator U1A is higher than the inverting terminal, and the voltage comparator U1A outputs a high level, generating a rising edge signal acting on the CP 1 pin of the trigger U2A, so that the Q1 pin of the trigger U2A becomes a high level. After passing through the single-channel MOSFET gate driver circuit U3, the high level signal drives the field effect transistor Q1 to turn on; The capacitor C10 is charged by the power supply VCC0 and the charging current limiting resistor R8. The two ends of the capacitor C10 are connected in parallel with the voltage dividing resistors R9 and R10. The voltage divided signal at both ends of the capacitor is transmitted to the voltage comparator U5A and compared with the set reference voltage. After the field effect transistor Q1 is turned on and charged, the voltage across the capacitor C10 rises. When the voltage across the capacitor C10 exceeds the set reference voltage, that is, the upper limit of the charging voltage, the non-inverting input terminal of the voltage comparator U5A is higher than the inverting input terminal, and the output is a high level; The high level is transmitted to the reset pin CD1 of the trigger U2A, and the Q1 pin of the trigger U2A outputs a low level. The low level signal drives the field effect transistor Q1 to turn off after passing through the single-channel MOSFET gate driver circuit U3, and controls the upper limit of the charging voltage of the capacitor C10 to the set reference voltage; the controller determines the capacitance value of the discharge circuit according to the special processing requirements of the real-time variable pulse energy of the processed parts, outputs the capacitor group path control signal to the capacitor group circuit, and controls the path of the working capacitors C10~C1n of the capacitor group circuit; Since the paths of capacitors C10 to C1n correspond to capacitors of different values, it is possible to obtain discharge circuit capacitors of different sizes; At the same time, the controller outputs the displacement and direction control pulse signal of the stepper motor 57CM23 according to the determined variable resistance value; The stepper motor displacement pulse control signal output by the controller to the stepper motor driver M542C is input from the PUL pin; The stepper motor direction control pulse control signal output by the controller to the stepper motor driver M542C is input from the DIR pin; The stepper motor enable signal output by the controller to the stepper motor driver M542C is input from the ENA pin; The stepper motor 57CM23 rotates a specified angle under the control of the displacement and direction enable signal input by the controller to the stepper motor driver M542C, thereby controlling the variable resistance to a specified value; the displacement signal is a periodic electric pulse signal output by the controller STM32F103, the controller STM32F103 is connected to the stepper motor driver M542C through a lead, the periodic electric pulse signal is transmitted to the displacement interface of the stepper motor driver M542C through the lead, and the stepper motor 57CM23 is driven to rotate after being processed by the stepper motor controller M542C; the enable signal is an electric pulse output by the controller STM32F103, which is transmitted to the enable control port of the stepper motor driver M542C through the lead to control the rotation or emergency stop of the stepper motor, and is used to control the stepper motor, prevent overshoot during operation, and ensure the accuracy of the stepper motor positioning; The direction control signal is the same as the enable signal, which is an electrical pulse signal output by the controller STM32F103 and transmitted to the driver direction control interface through the lead. During the operation of the pulse power supply, the variable resistance value needs to be increased or decreased in real time. Therefore, the stepper motor that controls the variable resistance needs to be able to achieve real-time commutation. The role of the direction control signal is to realize the commutation operation of the stepper motor through the controller; the variable pulse energy requirement refers to the change of the processing cross-sectional area during the processing. Different materials correspond to different unit area current density values. The product of the unit area current density value and the cross-sectional area can determine the peak current of different cross-sections. The discharge energy that can be stored on the capacitor can be expressed as: Where Vs refers to the charging voltage of capacitor C, so the pulse energy is proportional to the capacitance value; Another way to express the discharge energy is: u(t), i(t) refer to the discharge voltage and discharge current respectively. The discharge time T is the maximum pulse width. The discharge energy is related to the discharge voltage, discharge current and discharge time. In actual discharge, the discharge voltage is basically constant, so the peak current in the set pulse width range determines the maximum discharge energy; The maximum discharge energy is equal to the energy stored in the capacitor, so the above two discharge energy formulas are equal. In this way, the required capacitance value can be calculated based on the previously determined discharge peak current. Determination of the value of variable resistor R2: Changing the value of the variable resistor R2 can change the discharge current as follows: The discharge current can change the radius of the discharge cross-sectional area through the discharge energy and the discharge gap, so the variable resistor R2 has a corresponding relationship with the target discharge machining size, where U refers to the discharge voltage and t refers to the discharge time.

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