(1) Increased Power Loss: Leakage flux does not pass through the transformer core but spreads through the surrounding air, leading to energy loss and reduced efficiency.
(2) Voltage Drop: Leakage flux generates leakage reactance, which can cause voltage drops, especially under load changes or short-circuit conditions.
(3) Increased Temperature Rise: Power loss due to leakage flux raises the transformer’s temperature, potentially affecting its long-term stability and lifespan.
(4) System Harmonic Interference: Leakage flux may introduce harmonics that interfere with other equipment in the power system, leading to instability.
Calculation Methods for Leakage Flux
(1) Short-Circuit Test:
The short-circuit test measures leakage reactance. By short-circuiting the low-voltage side and applying a small voltage to achieve rated current, leakage reactance can be calculated.
Leakage Reactance (
): Leakage reactance is calculated using 
,where 
is the short-circuit test voltage and 
is the short-circuit current.
(2) Open-Circuit Test: The open-circuit test helps determine the transformer’s flux and magnetic field strength but is less direct for measuring leakage flux. It mainly measures magnetizing current and core loss.
(3) Mathematical Modeling:
Estimation of leakage reactance can be done through mathematical modeling of the transformer’s geometry and winding layout using electromagnetic field models.
Leakage Inductance (
): Leakage inductance can be estimated using 
, where 
is the leakage flux and 
is the leakage current.
Reducing Leakage Flux
(1) Optimize Winding Design: Designing winding structures with higher density and minimized gaps can reduce leakage flux. A more compact winding layout also helps in decreasing leakage flux.
(2) Improve Core Structure: Using high-quality magnetic materials, such as high-permeability silicon steel, increases core magnetic permeability and reduces leakage flux. A well-designed core ensures most flux passes through it.
(3) Enhance Winding Insulation and Shielding: Using high-quality insulation and shielding techniques reduces the impact of leakage flux. Shielded windings can also minimize leakage flux interference with external circuits.
(4) Reduce Air Gaps and Optimize Structure: The air gap and structural design of the transformer significantly affect leakage flux. Reducing air gaps and optimizing the overall design can help minimize leakage flux.
(5) Select Appropriate Transformer Model: Choosing a transformer model based on actual load and application needs can reduce the impact of leakage flux on performance. Different types and specifications have varying leakage flux characteristics.
