Welding Transformer Rectifier Control for Magnetization Prevention
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Solution Overview
Problem
Welding transformers face issues with magnetization effects during resistance welding, leading to contamination and system malfunctions, and existing solutions such as thyristor rectifiers are inefficient and cumbersome, while alternative methods like polarity switching with additional cables increase complexity and risk.
Innovation Solution
A device with two rectifier branches, each containing a transistor module connected between the welding transformer and the welding electrode, which alternates between operating modes to prevent short circuits and magnetization, allowing for efficient polarity switching without additional cables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a thyristor rectifier is used to avoid magnetization effects, then magnetization is prevented, but installation space doubles and operating characteristics deteriorate
Solution Approach 1:
The rectifier is divided into two separate rectifier branches (first and second rectifier branches), each with its own transistor module. This segmentation allows selective activation of individual branches to achieve polarity switching without requiring a complete four-thyristor rectifier configuration, thereby reducing installation space while preventing magnetization.
Solution Approach 2:
The system dynamically switches between different operating modes by activating or deactivating specific transistor modules (first and second transistor modules in first branch, third and fourth transistor modules in second branch). This dynamic control enables polarity reversal to prevent magnetization without the permanent space requirement of a full four-thyristor rectifier.
2Object-affected harmful factors
If a thyristor rectifier is used to avoid magnetization effects, then magnetization is prevented, but power losses increase and power output decreases
Solution Approach 1:
The invention changes the operating parameters by using transistor modules with freewheeling diodes instead of thyristors, and by implementing specific switching sequences that optimize current flow paths. This reduces power losses while maintaining the ability to prevent magnetization through polarity switching.
Solution Approach 2:
The freewheeling diodes ensure continuous current flow during switching transitions, preventing interruptions and reducing energy losses. The controlled activation of transistor modules maintains continuous useful action while enabling polarity reversal to prevent magnetization.
3Object-affected harmful factors
If polarity switching with additional cables is implemented, then magnetization is prevented, but system complexity and cable defect risks increase
Solution Approach 1:
The rectifier system performs polarity switching autonomously through its internal transistor module configuration and control logic. The first and second rectifier branches with their respective transistor modules can switch polarities without requiring external cable reconfiguration or additional signaling cables, thereby reducing system complexity while preventing magnetization.
4Area of stationary object
If transistor modules are used for polarity switching, then installation space is reduced, but short circuits can occur in secondary windings
Solution Approach 1:
Freewheeling diodes are connected in parallel with each transistor module to provide a safe current path during switching transitions. This beforehand cushioning prevents voltage spikes and short circuits in the secondary windings that could occur during polarity switching, while maintaining the space-efficient transistor-based design.
Solution Approach 2:
The control device monitors the operating state of the transistor modules and switching conditions, providing feedback control to prevent short circuits. By detecting potential short circuit conditions and adjusting switching timing, the system maintains reliability while benefiting from the reduced installation space of the transistor module configuration.
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 effectively prevents short circuits and magnetization, reducing system complexity, costs, and space requirements, while maintaining high power efficiency and reliability.
Implementation Method 1
welding transformer (30) with a primary winding and a secondary winding
Implementation Method 2
The direct current during welding can cause magnetization of the welded parts
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A device (35) and a method for controlling a rectifier (40) for a welding transformer (30) are provided. The rectifier (40) has two rectifier branches, in each of which at least one transistor module (Q5, Q6; Q5 to Q8) is connected between a secondary winding of the welding transformer (30) and a welding electrode (11; 12) of a welding tool (10). The device (35) is configured to determine at least one predetermined electrical boundary condition (UQ5; IQ5; UQ6; IQ6; T_Q13; T_Q24; T_s; T_M) during the operation of at least one transistor module (Q5, Q6; Q5 to Q8) of the rectifier (40), wherein the rectifier (40) is alternately switched to a first operating mode or a second operating mode during operation, with the transistor modules (Q5, Q6;Q5 to Q8) of the two rectifier branches are switched on in the first operating mode of the rectifier (40) when no power is supplied to the primary side of the welding transformer (30), and wherein alternately only one of the two rectifier branches is switched on in the second operating mode of the rectifier (40) when power is supplied to the primary side of the welding transformer (30) for a predetermined time period (T_Q13; T_Q24) for welding, wherein the device (35) is configured to determine a switch-off time (t2; t3; t4; t5; t6) of at least one transistor module (Q5, Q6; Q5 to Q8) in the operation of the rectifier (40) based on the determined at least one electrical boundary condition (UQ5; IQ5; UQ6; IQ6; T_Q13; T_Q24; T_s; T_M) and the current operating mode of the to determine the rectifier (40) in order to prevent a short circuit of the secondary windings of the welding transformer (30).