Capacitor Discharge Welding Circuit Without Transformers
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Solution Overview
Problem
Existing capacitor discharge welding circuits are cumbersome due to the use of transformers, which increase cost, weight, and heat, and silicon controlled rectifiers (SCRs) that fail to disconnect immediately from the input voltage source, limiting voltage regulation and safety compliance, especially at varying input voltages.
Innovation Solution
A capacitor discharge welding circuit utilizing a rectifier bridge, capacitor charge switches, and capacitor discharge switches, along with voltage sensors and a control system, eliminates the need for transformers and SCRs, allowing for immediate disconnect and voltage regulation through relays and solid-state switches, and a buck-boost converter for voltage adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transformer is used in the capacitor discharge welding circuit, then safety isolation and voltage transformation functions are achieved, but the device weight, cost, and heat generation increase
Solution Approach 1:
The patent removes the transformer from the circuit entirely, extracting the heavy component while replacing its functions with alternative components (solid state switches, rectifier bridge, capacitor bank) that achieve the same safety isolation and voltage transformation without the weight penalty
Solution Approach 2:
The mechanical/electromagnetic transformer system is replaced with an electronic switching system using solid state switches and a rectifier bridge, substituting a heavy electromagnetic device with lighter electronic components that perform the same functions through semiconductor switching
2Reliability
If silicon controlled rectifiers (SCRs) are used to disconnect the capacitor from input voltage source, then isolation function is achieved, but immediate disconnection cannot be accomplished due to current threshold limitations
Solution Approach 1:
The patent removes SCRs from the circuit and replaces them with solid state switches that can be turned off immediately by controlling their gate signals, eliminating the fundamental limitation of SCR current threshold requirements for turn-off
Solution Approach 2:
The SCR switching mechanism is replaced with solid state switch technology that allows for immediate turn-off capability through electronic control, substituting a device with inherent delay limitations with one that provides instantaneous response
3Reliability
If SCRs are used for input power isolation, then isolation is achieved, but compliance with IEC 60974-1 overvoltage requirements requires expensive specialty SCRs with high blocking voltage ratings
Solution Approach 1:
The patent removes SCRs from the circuit entirely and replaces them with solid state switches and a rectifier bridge configuration that naturally handles overvoltage conditions, eliminating the need for expensive specialty SCRs with high blocking voltage ratings
Solution Approach 2:
The patent uses standard, readily available solid state switches and rectifier components instead of expensive specialty SCRs, opting for common components that can be easily replaced if needed rather than investing in costly, specialized parts
4Device complexity
If transformer-free SCR controlled capacitor charging circuit is used, then voltage regulation above rectified input AC power cannot be achieved, but circuit simplicity is maintained
Solution Approach 1:
The patent uses solid state switches that can be dynamically controlled to regulate capacitor charging voltage, allowing the system to adapt and provide voltage regulation above the rectified input AC power level through electronic switching control
Solution Approach 2:
The patent changes the operating parameters of the capacitor charging circuit by using solid state switches with variable duty cycle control, enabling the capacitor voltage to be regulated to levels higher than the rectified input AC power through pulsed charging sequences
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
This solution reduces the weight and cost of the welding circuit, enhances voltage control, and ensures safety compliance across a wide range of input voltages, enabling efficient and reliable welding operations.
Implementation Method 1
a rectifier bridge of diodes receiving the input voltage source
Implementation Method 2
at least one capacitor linked with the at least two capacitor charge switches
Implementation Method 3
an arc is produced by the rapid discharge of stored electrical energy in a capacitor to a fastener to be welded. The stored electrical energy vaporizes a small projection at the end of a fastener
Data Source
AI summary
A capacitor discharge (CD) fastener welding circuit including: an input voltage source; a rectifier bridge of diodes receiving the input voltage source; at least two capacitor charge switches linked with the rectifier bridge; at least one capacitor linked with the at least two capacitor charge switches; and at least two capacitor discharge switches linked with the capacitor and to welding output terminals.