| Company | Bombardier Transportation |
| Location Europe | Europe |
| Timeline | 1996 onwards |
| Project Overview | MIDEL 7131 has powered Bombardier’s TRAXX locomotives since the late 1990s, delivering reliable transformer performance for cross-border rail operations across Europe. |
| Product | Midel 7131 Synthetic Ester Transformer Fluid |
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This is a MIDEL case study.
Overview
Since the mid-1990s, Bombardier Transportation—originally operating as AdTranz—has relied on MIDEL 7131 to support its electric locomotive platforms. These locomotives are the backbone of European rail, moving both freight and passengers across multiple countries, power systems, and operating conditions.
At the heart of these trains are traction transformers, responsible for converting overhead line power into usable energy for motors and onboard systems. MIDEL 7131 has been used not only as the transformer fluid, but in some cases also as a coolant for converters, helping to keep critical systems running efficiently.
This long-standing relationship began with early locomotive designs and continues today, especially within the widely used TRAXX platform.
Challenge
Designing locomotives for Europe is far from simple. Operators needed trains that could:
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Run across borders, handling different electrical systems (15kV and 25kV AC)
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Deliver high power output (up to 5,600kW) for both freight and passenger use
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Perform reliably in continuous, demanding service
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Maintain safety in compact onboard spaces
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Withstand extreme operating conditions over long service lifetimes
On top of that, reliability was critical. Any failure could disrupt rail networks, delay cargo, or inconvenience passengers across multiple countries.
Solution
MIDEL 7131 was selected as the dielectric fluid for traction transformers across Bombardier’s locomotive platforms.
The technology was first proven in earlier designs, such as the Class 101, and then scaled up significantly with a major milestone:
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In 1998, AdTranz secured an order to supply 400 BR185 locomotives for Deutsche Bahn
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These formed the foundation of what became the TRAXX system—a modular locomotive platform designed for international use
The TRAXX platform allowed locomotives to operate seamlessly across different rail networks. MIDEL 7131 played a key role in this flexibility by ensuring safe and consistent transformer operation under varying voltages and loads.
Today, more than 850 TRAXX AC locomotives, and over 1000 units including multi-system variants, operate across Europe using MIDEL-filled transformers.
Benefits
The use of MIDEL 7131 has delivered clear, long-term advantages:
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Outstanding Reliability: Proven performance over decades of continuous rail operation
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Cross-Border Flexibility: Stable operation under different voltage systems
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Enhanced Safety: Fire-safe properties reduce risk in confined locomotive environments
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Thermal Performance: Effective cooling supports high-power applications
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Low Maintenance Concerns: Consistent fluid performance reduces operational issues
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Versatility: Suitable for both transformer insulation and converter cooling
Results
Since entering service, TRAXX locomotives equipped with MIDEL 7131 have built a strong reputation for dependability across Europe.
These trains operate on major international corridors, including routes running from Germany through Austria into Hungary, such as those used by Floyd zRT freight services. Despite the demanding nature of these routes, the results speak for themselves:
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No reported issues with the transformer fluid
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Excellent long-term reliability record
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Consistent performance across thousands of journeys and varying conditions