Transformer Shield Cylinder for Interference Reduction
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Solution Overview
Problem
Transformers with high-voltage primary and low-voltage secondary windings in tubular arrangements face challenges in reducing electromagnetic interference radiation, particularly at high frequencies, due to low input impedance, which is more pronounced in layer winding configurations compared to coil windings.
Innovation Solution
Incorporating a shield cylinder with electrically conductive layers, such as ring bands and longitudinal bands, connected to a ground contact, between the high-voltage primary and low-voltage secondary windings, forming a braided shielding arrangement that reduces capacitive coupling and increases impedance, thereby minimizing interference radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a layer winding configuration is used for the high-voltage primary winding, then the manufacturing complexity is reduced compared to coil windings, but the input impedance decreases above the cut-off frequency, leading to increased electromagnetic interference radiation
Solution Approach 1:
A shield cylinder is introduced as an intermediary component between the high-voltage primary winding and the low-voltage secondary winding. This shield cylinder includes a conductive shielding layer that is electrically connected to ground, acting as a mediator to modify the electrical field distribution and reduce capacitive coupling, thereby increasing input impedance and reducing electromagnetic interference radiation while allowing the use of simpler layer windings
Solution Approach 2:
The invention changes the electrical field distribution parameter by introducing the shield cylinder with conductive shielding layer grounded between the windings. This parameter change increases the capacitive component of the input impedance above the cut-off frequency, thereby reducing electromagnetic interference radiation without requiring a change in winding configuration
2Reliability
If the capacitance of the high-voltage primary winding is increased, then the input impedance decreases, but the electromagnetic interference radiation increases
Solution Approach 1:
The shield cylinder modifies the electrical field distribution and changes the capacitive coupling parameters between windings. By adjusting the capacitance parameter through the introduction of the grounded shielding layer, the input impedance is increased above the cut-off frequency, thereby reducing electromagnetic interference radiation
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 braided shielding effectively reduces radiated interference power at high frequencies by increasing the capacitive component of the input impedance, allowing for the use of layer windings while maintaining compliance with interference limits, thus simplifying production and reducing costs.
Implementation Method 1
By arranging an electrically conductive surface connected to the earth contact of the transformer between the high-voltage primary winding and the low-voltage secondary winding, the distribution of the electrical field between them is changed. This change in the electrical field causes a reduction in the electrical capacity of the high-voltage primary winding.
Implementation Method 2
The concentric arrangement of the high-voltage primary winding and the low-voltage secondary winding causes, in addition to the inductive coupling between the two windings, the formation of an electrical capacitance in the manner of a cylinder capacitor.
Implementation Method 3
At a given operating frequency, the power of the electromagnetic interference radiation increases as the input impedance of the transformer decreases.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The transformer (T) has a high voltage primary winding (4) i.e. layer winding, and a low voltage secondary winding i.e. traction secondary winding (3), provided in a pipe winding arrangement. A shielding cylinder (6) is concentrically arranged between the primary winding and the secondary winding. The shielding cylinder includes an electrically conductive shielding layer (6.3), which is approximately concentric to a cylinder casing surface. The shielding layer is electrically connected with a ground contact of the transformer, and provided with a ring band and an elongate band. An independent claim is also included for a method for manufacturing a transformer.