In the world of high-voltage power equipment, silence is golden—but difficult to achieve. At KONČAR – Distribution and Special Transformers, reducing industrial noise has become a strategic priority. As a European leader in distribution, special and power transformers manufacturing, KONČAR – D&ST is known for delivering high-performance, reliable transformers to more than 100 countries.

With installations in urban centers, industrial hubs, and residential zones, acoustic performance is not a secondary consideration; it’s a core requirement.

To address rising regulatory and customer expectations for low-noise equipment operation, KONČAR – D&ST made a strategic decision to replace costly and time-consuming physical prototyping with a “simulation-first” approach.   

Guided by their internal engineering vision and with support from simulation experts at SciEngineer, KONČAR – D&ST developed a detailed virtual prototype using COMSOL Multiphysics®. This enabled their team to explore acoustic behavior under real operating conditions, test design modifications digitally, and validate performance improvements with a high level of confidence. The result: a smarter, faster path to quieter transformers, and a blueprint for future innovation.  

Key takeaways

• Achieved nearly 10% perceived loudness decrease, while maintaining magnetic and structural performance targets. 

• Validated acoustic models against real-world measurements, with less than 2 dB deviation and under 5% error across both open- and short circuit scenarios.  

• Applied IEC 61672, 1:2013 standards for A-weighted sound pressure level calculation to ensure compliance with regulatory requirements. 

• Identified high-impact design changes, including stiffener optimization, and core material treatment through uncertainty and sensitivity studies, and  

• Enabled rapid design iteration without physical prototypes, reducing risk, accelerating development timelines, and cutting potential compliance-related costs.  

Challenges

R&D team needed to reduce transformer noise emissions to comply with regulatory limits and meet customer expectations. However, the underlying problem wasn’t just about loudness— it was more complex.  

Transformer hum originates from vibrations in various parts of the device. The primary contributors are a metal core with coils wound around each section, protective tank, and insulating oil within the tank. The alternating current flowing through the coils generates magnetic fluxes that cause mechanical strains in the magnetostrictive core. Since the magnetic fluxes alternate directions, the core experiences rapid growth and shrinkage. This process generates vibrations that propagate through the insulating oil, reaching the tank and the core’s attachment points. Additionally, the alternating currents create load noise due to Lorentz forces from coil windings.  

The challenge wasn’t just predicting sound; it was understanding how geometry, material damping, magnetic, and mechanical behavior combined to produce it.  

“We had limited ability to test physical variants. Simulation gave us the chance to explore ideas quickly and reliably,” said a senior R&D engineer involved in the project.  

Additionally, defining the damping behavior of structural components and estimating magnetostriction parameters based on real-world measurements were also challenging tasks. Getting these material properties right was key to any realistic simulation.  

Solution

SciEngineer stepped in with deep expertise in COMSOL Multiphysics®, acoustic modeling, and uncertainty analysis. The project kicked off by importing the existing CAD geometry and several sets of acoustic measurements, captured both with and without the transformer tank.  

SciEngineer’s team developed a multiphysics COMSOL model that combines magnetic fields (mf), solid mechanics (solid), shell and pressure acoustics, and pressure acoustics frequency domain (acpr) interfaces, which the team used in frequency domain simulations to capture the fundamental behavior of the transformer. Then, a time-dependent study was conducted to calculate the A-weighted sound pressure level. The geometry was replicated from STEP files, and measurement positions were added, including various distances and heights from the transformer. Typical test scenarios, such as open-circuit- and short-circuit tests, were implemented in the tool. For transient acoustic problems, various sound pressure level metrics were defined in the literature and measurement standards. These metrics are important to be aware of when comparing the results of a transient acoustic simulation to the measurements of a sound level meter, or when trying to make results from a transient simulation easier to interpret on a logarithmic scale. With the help of one of the core functionalities of COMSOL Multiphysics, the pressure signal’s FFT was easily calculated.    

• Open-circuit and short-circuit operating conditions  

• Sound propagation and reflection in air  

• Acoustic pressure levels at standardized measurement positions  

We applied the IEC 61672, 1:2013 standard to calculate A-weighted sound pressure levels to ensure alignment with international norms and enable “apples-to-apples” comparisons with physical test results.  

https://www.comsol.com/model/transient-sound-pressure-level-105481  

Simulations typically assume that input data are fixed, and that outputs can be computed with high accuracy. However, this deterministic approach does not account for the variability present in practical scenarios such as manufacturing processes, where significant uncertainty exists.  

Our engineers used to analyze the effects of this uncertainty on their simulations. It provides tools to explore input parameters — such as physics settings, material properties, and geometric dimensions — and assess their impact on quantities of interest (QoIs).  

The results pointed to specific high-impact modifications:  

• Identifying the Optimal Structural Stiffness  

• Damping opportunities: Certain structural areas lacked stiffness, making them prone to resonance; and  

• Material Treatment Effects: Achieving the Optimal Balance of Isotropic and Orthotropic Properties 

Results

The improved design managed to reduce the emitted noise, equivalent to a nearly 10% decrease in perceived loudness. In acoustic engineering, that’s a major gain, especially without alteration of the magnetic or thermal performance of the transformer.  

The simulation results were in good agreement with the test data, with a deviation under 5% and less than 2 dB in all scenarios. Once refined, our results consistently stayed within measurement error margins.  

Additional simulations, such as vacuum tests and deformation analysis under open-circuit conditions, confirmed that the structural integrity of the tank had been preserved. 

Read more about KONČAR – Distribution and Special Transformers

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