EDM Power Supply Circuit Topology for High Peak Current
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Solution Overview
Problem
Current sinker electric discharge machining power supply devices face limitations in supplying current pulses with high peak current and short ON time, leading to restricted material removal rates and wear rates due to heat generation and complex circuitry requirements.
Innovation Solution
A power supply device with a DC power supply, current sensor, and switching elements controlled by a pulse controller to manage gap current, eliminating the need for current limiting resistors and allowing for steep rising edges and high peak currents, enabling improved material removal rates and reduced wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If current pulses with high peak current and short ON time are supplied to increase material removal rate, then productivity is improved, but heat generation increases causing device complexity and reliability issues
Solution Approach 1:
The patent extracts and eliminates the current limiting resistor from the electric discharge machining circuit. By removing this component, the system can supply current pulses with high peak current and short ON time without the limitations and heat generation problems associated with resistor-based current limiting, thereby improving productivity while reducing device complexity
Solution Approach 2:
The patent changes the current pulse parameters by enabling high peak current (20A or more) and short ON time (about 10 μs) through the elimination of the current limiting resistor. This parameter change allows for high-frequency repetitive discharge with steep rising and falling edges, directly improving material removal rate without the thermal constraints of conventional resistor-based systems
2Device complexity
If current limiting resistors are used to control gap current, then device complexity is reduced, but energy loss increases and peak current is limited
Solution Approach 1:
The patent removes the current limiting resistor from the circuit, eliminating the energy loss that occurs in resistor-based current limiting. The switching elements control gap current without the continuous power dissipation inherent in resistor-based systems, significantly reducing energy loss while maintaining circuit simplicity through the use of standard switching components
Solution Approach 2:
The patent employs periodic switching action using switching elements that turn on and off at high speed to control gap current. This periodic control method replaces continuous resistor-based current limiting, allowing current to flow only when needed during the discharge cycle, thereby minimizing energy loss while maintaining effective current control
3Productivity
If switching elements are turned on and off at high speed to supply current pulses, then productivity is improved, but heat generation reduces responsiveness and may damage switching elements
Solution Approach 1:
The patent maintains continuous control of the discharge process by using switching elements that can be turned on and off at high speed. The elimination of the current limiting resistor allows for more efficient current control during each discharge cycle, enabling higher frequency operation while the switching elements remain within their operational limits, thus maintaining both productivity and reliability
Solution Approach 2:
The patent uses a chopping circuit that monitors gap current and provides feedback control. The chopping circuit interrupts current flow at regular intervals after reaching a set peak current, creating a controlled feedback mechanism that prevents excessive current and heat generation while maintaining high-frequency pulse capability, thereby protecting switching elements while maximizing productivity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides current pulses with high peak current and steep rising edges, enhancing material removal rates and allowing for higher voltage operation without complex circuitry, thus improving machining efficiency and reducing wear on tool electrodes.
Implementation Method 1
If a power supply applies a voltage to the machining gap, the dielectric fluid is ionized. Then, electric discharge is generated across the machining gap
Implementation Method 2
electric discharge is generated across the machining gap and an ON time (alternatively called duration time) starts
Implementation Method 3
a first switching element connected in series between the DC power supply and the tool electrode; a first reverse current prevention diode connected in parallel with the DC power supply and connected in series with the machining gap and the first switching element
Implementation Method 4
a pulse controller for controlling the first and second switching elements in response to gap current, having ON time and peak current
Data Source
Figure 1
Figure 2(A)~2(C)
AI summary
A power supply device comprises a DC power supply (12), a current sensor (14) for detecting gap current (Igap) flowing through the machining gap, a first switching element (16) connected in series between the DC power supply and the tool electrode (2), a first reverse current prevention diode (22) connected in parallel with the DC power supply and connected in series with the first switching element (16), a second switching element (18) connected in series between the DC power supply and the workpiece (3), a second reverse current prevention diode (24) connected in parallel with the DC power supply and connected in series with the second switching element (18), and a pulse controller (20) for controlling the first and second switching elements in response to gap current (Igap). From a first time (t1) when electric discharge is generated across the machining gap, until a second time (t2) when the gap current reaches the peak current during the ON time, both of the first and second switching elements are on. At the second time (t2) only one of the first and second switching elements is turned off.