EMC & eMobility

CONTENTS

1. Introduction
2. Basics
3. e-Motors
4. Battery Testing
5. Summary

Note: This article is an abridged version of the white paper “EMC and eMobility” published in 2024 by MVG, available at www.mvg-world.com. The full paper provides expanded technical detail and includes additional coverage of EV charging, which is only briefly referenced here for succinctness.

Introduction

eMobility combines electric powertrains, communication technologies, and charging infrastructure to enable the propulsion of electric vehicles.

Growing demand for EVs, driven by climate change and Net Zero objectives, has led to rapid expansion of EMC regulatory requirements from organisations such as IEC, CISPR, ISO, SAE, GB/T and UNECE.

While traditional automotive EMC practices are mature, EVs introduce new testing needs in three key areas: eMotors, EV charging systems, and EV batteries.

These requirements influence the design of EMC facilities, which may range from compact CISPR 25 chambers for component-level tests to large 10-meter semi-anechoic chambers for full vehicle testing.

This paper outlines these applications and the additional infrastructure needed to support EMC testing for modern electric vehicles.

EV Basics

Electric vehicles use energy stored in batteries to power electric motors, providing quiet, emission-free propulsion and fast acceleration. Key components include the electric motor, inverter, drivetrain, battery pack, and charging interface.

Increasingly, these elements are integrated into a compact eAxle unit combining the motor, inverter, and transmission. Although future designs may favour inverter-free, DC-only systems, today’s infrastructure still relies mainly on AC charging.

E MOTORS

In this section we will look at how EV motors are tested, otherwise known as eMotor testing, starting with the regulatory EMC standards that drive this work.

EMC STANDARDS

CISPR 25 Ed.5 (2021) introduces high-voltage EMC test methods for electric and hybrid vehicles, particularly through Annex H, which defines radiated emissions setups for systems powered by shielded HV supplies with an eMotor attached.

Compared with standard CISPR 25 benches, these setups require a chamber with additional width—typically around 2 meters—to accommodate the motor and dynamometer, along with an HV filter linking the chamber to the external high-voltage supply.

ISO 11452-2 (2019), which specifies radiated immunity testing in absorber-lined chambers, uses a nearly identical test configuration for high-voltage systems. This allows emissions (CISPR 25) and immunity (ISO 11452-2) tests to be performed in the same chamber without reconfiguring the EUT.

However, immunity testing requires larger antennas, meaning the chamber must be dimensioned to handle the increased physical size of the test equipment.

Test methods for power supply systems for high voltages in electric and hybrid vehicles. Radiated emission – Example of test setup measurement with biconical antenna for EUTs with shielded power supply systems with electric motor attached to the bench.

E MOTOR TEST SOLUTIONS

Introduction

Having reviewed the above EMC standards for EV motors, let us now look at the two main types of eMotor EMC test setups. These apply to single-axle motors and differ primarily in how the dynamometer is installed:

• Fixed systems use a permanently mounted dynamometer, with part of the unit positioned outside the chamber, and are suited for high-power eMotors.
• Mobile systems place the entire dynamometer on a movable bench inside the chamber and are intended for lower-power motors.

Each configuration supports the required EMC testing but differs in flexibility, cost, and power-handling capability.

eMotor testing – FIXED solutions

The fixed test setup is designed for high-power eMotors, typically ranging from 120 kW to more than 500 kW and producing 200–5000 Nm of torque. Because of these high power and torque levels, the dynamometer must be extremely stable, with part of the unit installed outside the chamber and part inside.

A shielded rotating shaft connects both sections, allowing full torque transfer while maintaining EMC shielding integrity. The dynamometer usually sits on concrete foundations to minimise vibration.

Power for the test is supplied by a high-voltage battery emulator rated around 1000–1200 V and 500–1000 A, which provides charge, discharge, drive, and brake modes.

This HV supply is located outside the chamber and connects through a high-specification HV AC/DC RF filter that maintains shielding performance while delivering the required electrical power.

eMotor testing – Mobile solutions
For eMotors with power levels below approximately 125 kW—and more commonly around 60 kW—it is typical to employ a mobile test bench for EMC testing.

In the schematic shown in Figure 4, the low-power dynamometer is positioned entirely inside the chamber. This is possible because the required mechanical stability for these power and torque levels can be achieved using a mobile CISPR 25 ground-plane test bench.

In this configuration, the eMotor is mechanically coupled to the dynamometer inside the chamber, while high-voltage power is still supplied from outside the chamber through an HV RF filter, similar to higher-power solutions.

Typical specifications of such mobile test benches include:

• Maximum speed: ~10,000 rpm
• Torque capability: ~450 Nm
• Dimensions: approx. 2.5 × 1.2 × 1.5 m (L × H × W)
• Mass: approx. 2 tonnes

Below in Table 1 is a comparison of the advantages and disadvantages of fixed and mobile eMotor test platforms.

eAXLE

Up to this point, the discussion has focused on EMC testing solutions for single-axle eMotors.

However, the industry has evolved with the introduction of a compact electric drive solution suitable for both battery-electric and hybrid applications: the eAxle, shown in Figure 5.

In an eAxle, the transmission, power electronics, and the electric motor are all integrated into a single, compact assembly that directly powers the vehicle’s axle.

This integration simplifies the overall drivetrain architecture and can reduce system cost. However, it does not simplify EMC testing. In fact, testing becomes more complex.

Because the eAxle includes a differential and delivers power through two output shafts, the test bench must be capable of loading both shafts simultaneously, with independent control of torque and speed.

Early industry solutions have been dual-dynamometer systems, in which each output shaft of the eAxle is coupled to its own dynamometer. This configuration allows:

• Independent torque loading on each shaft
• Precise speed control per output
• Accurate representation of real-world axle behaviour
• Full testing of the integrated inverter, motor, and gearbox under realistic load conditions

In Figure 6, examples of fixed and mobile eAxle test solutions are shown. As with single-axle solutions, the same general benefits and drawbacks apply:

• Fixed systems offer high mechanical stability and high torque capability but require significant floor space and cost.
• Mobile systems offer flexibility and lower infrastructure requirements but are limited in torque/power capacity.

For eAxle systems, however, both approaches carry an additional disadvantage: the need for a second dynamometer, which significantly increases the overall cost of the test bench.

It remains an open question whether the cost savings achieved by integrating three power units (motor, inverter, and transmission) into a single eAxle assembly fully offset the increased expense of testing such units in a dual-dynamometer configuration.

Furthermore, in 2025 the Chinese Standard GB/T 18655 introduced new set ups for eAxle testing as shown in the figs. 7a – 7f below. So far this has not been replicated in either CISPR 25 or ISO 11452-2 and to our knowledge it is not clear if these set ups have been widely implemented.

EV Battery Testing

EV batteries undergo many environmental tests, but from an EMC perspective the main requirements typically follow:

• CISPR 12
• CISPR 25
• ISO 11451 / ISO 11452
• UNECE R10
• Manufacturer-specific variants of R10

Most battery EMC tests can be performed in a chamber already used for CISPR 25 eMotor testing, with the battery placed on the ground-plane bench and HV/LV connections fed through RF filters. With suitable design, the chamber can support both eMotor and battery testing.

Battery EMC Test Configurations

Testing may be required at different levels:

• Stand-alone components
• Complete battery pack
• Vehicle-level integration
• Battery with BMS in full operation

Battery Management System (BMS)

The BMS controls the electrical and thermal behaviour of the battery and is a key safety component. Its main functions include:

• Keeping cells within safe limits
• Monitoring SoC and SoH
• Managing cell balancing
• Protecting against abnormal conditions
• Providing diagnostics to vehicle systems

EMC Chamber Design

Considerations for eMobility

As described in the previous sections, a wide range of EV component- and vehicle-level test applications must be conducted within an EMC chamber. When testing high-voltage EV systems, several specific factors must be considered to ensure both safe operation and accurate EMC performance, including:

• Mechanical integration of eMotors, eAxles, or battery packs
• High-voltage feedthroughs and appropriate RF filtering
• Proper grounding and bonding arrangements
• Thermal management and cooling requirements
• Overall chamber layout and configuration for test flexibility

AVAILABLE SPACE

Adequate space in the host building is essential when designing EMC facilities for eMobility. Even component-level eMotor testing requires a CISPR 25 chamber with extra width to accommodate the dynamometer and high-voltage supply, along with additional room for RF amplifiers and test instrumentation, which may each need their own shielded control rooms.

In some cases whole vehicle needs to be accommodated in the component test chamber (see fig. 10).

While some testing can be performed in a larger 3-meter SAC, most EV applications ultimately require a 10-meter SAC sized according to the largest vehicle under test, from motorbikes to heavy trucks and double buses.

The vehicle’s dimensions determine the turntable diameter and the layout of the chassis dynamometer or rolling road embedded within it—typically 6–10 meters wide—along with a shielded pit between 2 and 4 meters deep.

RF POWER FILTERS

RF power filters are required between the chamber’s internal electrical cabling and the external high-voltage supply to prevent unwanted electromagnetic signals from entering the shielded environment.

While all EMC chambers use such filters, eMobility applications demand much higher power capacities due to the large currents and voltages involved. Typical EV requirements can exceed 360 kW AC, 250 kW DC, AC charging up to 4 × 650 A at 480 V, and DC charging up to 1000 V/450 A.

As a result, these filters must be both electrically and physically large, occupying significant wall space and requiring careful integration into the chamber’s overall design.

ELECTRICAL CABLING

The large diameter and heavy weight of high-power electrical cables used in EV testing create significant routing challenges inside the chamber.

Their limited bend radius requires careful planning beneath the chamber floor to ensure safe and reliable installation. When power is needed on the turntable—for example, to support EV charging points—the turntable manufacturer must confirm compatibility.

In many cases, a specialised energy chain is required to manage cable movement during rotation, and this may also necessitate a deeper turntable pit to accommodate the cable routing.

HIGH VOLTAGE SAFETY

Given the high power levels involved in EV EMC testing, robust High Voltage Protection (HVP) measures are essential to ensure operator safety.

This includes implementing multiple hardware and software safety loops, integrating protective circuits within the high-voltage supply system, and providing emergency break-loop mechanisms for operators.

Additionally, the facility must include insulated HVP flooring and dedicated high-voltage feed points accessed through protected floor hatches. These measures ensure safe operation when working with high-energy EV systems.

Summary

The shift towards electric mobility is redefining EMC testing, introducing far greater power levels, integrated high-voltage systems, and increasingly complex components such as eMotors, eAxles, and advanced battery packs.

While the foundations of automotive EMC remain relevant, EV testing demands larger chambers, higher-capacity filtering, specialised dynamometer solutions, and robust high-voltage safety infrastructure.

As standards continue to evolve and powertrain technologies become more integrated, the design of EMC facilities must be forward-looking, scalable, and capable of supporting both current and emerging eMobility applications.

Investing in flexible, well-engineered test environments will be essential for ensuring compliance, safeguarding development timelines, and supporting the rapid innovation driving the future of electric transportation.