Benchmarking an EESM Motor Without Prior Data

Case Study: Benchmarking an Innovative EESM E-Motor Without Prior Data

Introduction: A Shifting Landscape in E-Motor Technology

Powertrain technology in the automotive sector continues to evolve rapidly, driven by innovations in materials, motor topologies, and control strategies. These advancements have led to an estimated 20% improvement in power density and overall efficiency in recent years.

Focusing specifically on e-motor technology, increasing power density has emerged as the central challenge. New architectures such as axial flux motors and high-speed rotors, reaching up to 25,000 rpm, are enabling significant reductions in size and weight. However, many of these motors depend on permanent magnets, raising concerns related to cost, availability, and geopolitical risk. In response, some OEMs are exploring magnet-free topologies such as externally excited synchronous motors (EESM), which offer a promising alternative. However, they also bring additional development requirements.

In this increasingly complex and fast-moving environment, maintaining flexibility in technology selection has become a critical strategic advantage. This is precisely where EPowerLabs adds value: by helping OEMs and Tier 1 suppliers carry out end-to-end validation campaigns, execute in-depth benchmarking studies, and apply expert engineering support based on automotive-grade methodology with the agility of a focused innovation partner.

Founded in 2020, EPowerLabs operates one of Europe’s largest electric powertrain test facilities at the MUBIL Center in San Sebastian, Spain. Since its inception, the company has completed more than 70 testing projects for over 25 global clients.

A Single Motor, No Documentation: Starting from Zero

A leading automotive Tier 1 approached EPowerLabs with a bold request: to benchmark an advanced electrically excited synchronous motor (EESM) used by a competitor. The complexity of the task was significant. No technical documentation, no electrical schematics, and no sensor or rotor excitation data were available. The only resource was a single physical motor. The objective was to uncover its performance profile, understand its physics, design the most suitable control strategy, and assess its suitability for future development projects.

A Single Motor, No Documentation: Starting from Zero

A leading automotive Tier 1 approached EPowerLabs with a bold request: to benchmark an advanced electrically excited synchronous motor (EESM) used by a competitor. The complexity of the task was significant. No technical documentation, no electrical schematics, and no sensor or rotor excitation data were available. The only resource was a single physical motor. The objective was to uncover its performance profile, understand its physics, design the most suitable control strategy, and assess its suitability for future development projects.

Building the Test Setup Through Reverse Engineering

The project began with a full reverse engineering phase. EPowerLabs identified the motor’s key components, such as the position sensor and rotor excitation system, and designed custom mechanical interfaces for mounting the motor on the test bench. A controllable DC/DC converter was added to manage rotor excitation, and a dedicated air-cooling system was implemented to ensure thermal stability during testing.

Despite working with unknown mechanical tolerances and interface constraints, the team successfully replicated a controlled environment suitable for high-precision measurement and experimentation. This phase also required iterative debugging to safely energize and rotate the motor, ensuring the integrity of each subsystem without damaging the hardware. Close attention was paid to electrical insulation and sensor alignment to avoid false readings or overloading components during the initial runs.

A Dynamic, Multi-Phase Test Campaign Tailored in Real Time

Once the motor was operational on the bench, a multi-phase testing campaign, including motor characterisation, motor model verification, and various efficiency runs, was launched. Early tests focused on verifying motor health and basic operation. The team then moved into detailed characterisation, performing electrical and thermal mapping under various load and speed conditions. Advanced control strategies such as MTPA (Maximum Torque per Ampere) and MTPV (Maximum Torque per Voltage) were implemented.

A major technical milestone was achieved by coordinating the AC inverter and rotor excitation supply to enable control of Id, Iq, and Idc simultaneously, which was critical for understanding the motor’s operating limits and efficiency.

These three degrees of freedom opened the door to different motor calibration strategies, such as maximizing efficiency by reducing machine losses, minimizing reactive power across the entire powertrain system, or even tuning the system for potential sport or eco driving modes.

In parallel, motor simulations helped reduce the testing scope and optimise runtime. These simulations were continuously updated with real-time measurements, allowing the team to refine the test matrix and focus on critical operating zones that revealed design intent or thermal bottlenecks.

Throughout the 10-week effort, EPowerLabs maintained close collaboration with the client, providing frequent updates and adjusting test priorities as results evolved. This agile, data-driven workflow allowed both teams to maximize value within a limited timeframe, adapting test goals to align with emerging findings.

From Unknown to Fully Characterized: Delivering Ready-to-Use Results

The project concluded with a comprehensive technical package: full efficiency maps, torque-speed curves, control calibration data, and detailed analysis of the motor’s operational behaviour. This information was delivered in a format compatible with the client’s own testing and validation platforms. Additional recommendations were provided for inverter tuning and control parameter adaptation in future vehicle integration phases.

Even without access to any OEM data, EPowerLabs successfully transformed an unknown motor into a fully benchmarked, ready-to-use system. The results gave the client not only insight into a competitor’s design but also a head start in applying similar concepts within its own development roadmap.

Conclusion: Why Independent Benchmarking Is a Competitive Advantage

This project highlights the strategic value of independent motor benchmarking in the fast-evolving automotive landscape. As electrification progresses and development cycles shorten, OEMs need reliable data to make technology decisions quickly and safely. Access to precise insights without relying on manufacturer documentation enables better validation and optimisation of new systems.

EPowerLabs showed that it is possible to deliver performance characterisations under pressure, combining technical expertise and agile test methods to create an integration-ready motor model from scratch. The ability to benchmark independently reflects not only engineering skill but deep alignment with real-world development demands.

In a sector where speed, reliability, and cost-efficiency are critical, independent benchmarking transforms uncertainty into confidence. It allows for faster iteration, lower technology risk, and stronger strategic planning. It is not just a competitive advantage; it is a vital asset for OEMs navigating electrification.

Frequently Asked Questions About EESM Motor Benchmarking

What is EESM motor benchmarking?

EESM motor benchmarking is the process of testing and characterising an electrically excited synchronous motor to understand its performance, efficiency, operating limits, thermal behaviour and control requirements.

Can an EESM motor be benchmarked without technical documentation?

Yes. Through reverse engineering, custom mechanical and electrical interfaces, controlled rotor excitation and a tailored test campaign, engineers can characterise an EESM even when no schematics, sensor data or manufacturer documentation are available.

What results can an EESM benchmarking campaign deliver?

A benchmarking campaign can deliver efficiency maps, torque-speed curves, electrical and thermal characterisation data, motor control calibration information, operating limits and recommendations for inverter tuning and vehicle integration.

Why do EESM motors require dedicated control strategies?

Unlike permanent-magnet motors, an EESM introduces controllable rotor excitation. Coordinating the inverter and rotor supply enables engineers to manage Id, Iq and rotor excitation current simultaneously and optimise efficiency, reactive power and driving-mode behaviour.

Why is independent electric motor benchmarking valuable for OEMs?

Independent benchmarking gives OEMs and Tier 1 suppliers reliable performance data without depending on manufacturer documentation. It supports faster technology decisions, reduces development risk and helps identify concepts that may be applicable to future powertrain programmes.