Auxiliary Core Mid-Point Connection for Transformer Leakage Reduction
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Solution Overview
Problem
High current harmonic distortion and increased losses in transformer structures used for twelve-phase rectifiers due to magnetic leakage and parasitic couplings, especially at high power levels, which affect efficiency and compactness.
Innovation Solution
A three-phase transformer design with a main magnetic core and an auxiliary core where the auxiliary core has a middle magnetic portion connecting the midpoints of each column, allowing independent closure of magnetic fields and reducing leakage, thereby forming two magnetically independent inductive half-cores within a single frame, minimizing magnetic leaks and losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a transformer with auxiliary core and primary windings wound on inductive core is used to filter output voltage and limit harmonic currents, then harmonic distortion is reduced, but magnetic leakage increases causing increased losses and reduced efficiency
Solution Approach 1:
The patent divides the auxiliary core into three separate columns, each supporting only one primary winding. This segmentation prevents out-of-phase currents from different windings from interacting and creating magnetic leakage loops, thereby reducing transformer losses while maintaining harmonic filtering capability
Solution Approach 2:
The patent extracts the primary windings from the inductive core columns and relocates them to the auxiliary core columns. This extraction eliminates the magnetic leakage phenomenon that occurred when windings were on the inductive core, reducing energy losses while preserving the harmonic current limiting function
2Power
If conductor strip width is increased to handle high current intensity, then current capacity is improved, but exposure to parasitic magnetic fields increases causing higher losses
Solution Approach 1:
The patent converts the previously harmful parasitic magnetic fields into beneficial confined magnetic circuits. By providing dedicated closed magnetic circuits on each auxiliary core column, the magnetic fields that would have been parasitic are now contained and utilized effectively, enabling high current capacity without increased losses
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
Significantly reduces transformer losses and harmonic distortion while maintaining compactness, enabling the use of metal strip conductors for high-intensity applications and improving the cancellation of harmonic components.
Implementation Method 1
the magnetic flux within the column is not homogeneous, and varies between the upper part and the lower part of the same column. The Applicant has thus observed that magnetic leakage phenomena occur, with a looping back of the magnetic field outside the circuit formed by the secondary core
Implementation Method 2
To ensure good magnetic coupling between the primary windings and the two series of secondary windings
Implementation Method 3
A first series of secondary windings is connected in star while the second series is connected in triangle, so that the voltage systems generated by these two systems are out of phase by 30°
Implementation Method 4
rectifier systems are known which are powered by a mains network delivering a three-phase voltage, and which generate a DC voltage
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
The invention relates to a three-phase transformer (10) for a twelve-phase rectifier including two three-phase, double-alternation rectifiers (3, 4) connected in parallel or in series, comprising: a main magnetic core (50) comprising three columns (51, 52, 53) connected magnetically in parallel at the ends thereof by two yokes (54, 55), and on each of which are wound: a pair of primary windings (11, 14; 12, 15; 13, 16) connected in parallel; two secondary windings (21-26), three of the secondary windings (21-23) wound onto separate columns being triangle-connected to the transformer terminals (31-33) connected to a first three-phase, double-alternation rectifier (3), the other three secondary windings (24-26) being star-connected to the transformer terminals (34-36) connected to the second three-phase, double-alternation rectifier (4); and an auxiliary core (60) comprising three columns (61, 62, 63) connected magnetically at the ends thereof by two yokes (64, 65) for closing the field, one of said pairs of primary windings (11, 14; 12, 15; 13, 16) being wound onto each of the columns, characterised in that the auxiliary core (60) comprises a median magnetic portion (69) connecting the mid-points of each column (61, 62, 63) located between two primary windings of the same pair (11, 14; 12, 15; 13, 16).