Due to their switching frequencies and power electronics, modern electric motors generate electromagnetic interference that can affect other devices. At the same time, electric motors themselves must be immune to external interference.
An EMC assessment during the development of electric motors saves time and money and prevents nasty surprises during certification. In today's networked world, where electric motors are increasingly being integrated into intelligent systems, EMC issues are becoming even more important.
The EMC challenge with modern electric motors
Modern electric motors, especially brushless DC motors and stepper motors, are operated almost exclusively with electronic controls. These power electronics work with high switching frequencies and steep edges, which generate broadband electromagnetic interference. In electric motors, interference is generated both via the supply lines and radiated via the motor housing and cables.
The problem is exacerbated by the trend towards higher power densities in electric motors. Compact designs lead to tighter tolerances and less space for EMC measures. At the same time, the requirements for electromagnetic compatibility are increasing, as electric motors are increasingly being used in sensitive environments.
EMC strategy for electric motors during development
A successful EMC strategy for electric motors begins in the concept phase. Instead of viewing EMC as a downstream task, electromagnetic aspects should be incorporated into the development of electric motors right from the start. This requires close co-operation between mechanical, electronic and EMC experts.
The first step is to define the EMC requirements for the electric motors. Which standards must be fulfilled? In which electromagnetic environment will the electric motors be used? These questions must already be answered when specifying the electric motors.
EMC-compliant design of electric motor systems
The mechanical design has a major influence on the EMC properties of electric motors. The motor housing acts as an antenna and can radiate or couple in interference. The electromagnetic properties of electric motors can be significantly improved by skilful housing design and shielding.
Cable routing for electric motors is a critical EMC aspect. Motor cables should be kept as short as possible and separated from sensitive signal lines. Twisted cables and shielded cables reduce both the radiation and the coupling of interference in electric motors.
Filter concepts for electric motors
Effective EMC filters are essential for the electromagnetic compatibility of electric motors. Both conducted and radiated interference must be taken into account. The filter design depends heavily on the specific application and the electric motors used.
Mains filters reduce the conducted interference from electric motors on the supply side. Motor filters between the control unit and electric motors reduce the high-frequency currents in the motor cables. Such filters are indispensable, especially for longer cables between the control unit and electric motors.
Standardised requirements for electric motors
The EMC requirements for electric motors are defined in various standards. The basic standard EN 61800-3 applies specifically to drive systems with electric motors and defines different categories depending on the area of application. Particularly strict EMC requirements in accordance with EN 60601-1-2 apply to electric motors in medical technology.
Conclusion: EMC as a success factor for electric motors
Electromagnetic compatibility is a critical success factor for modern electric motors. An EMC assessment during development saves time and money and leads to better products. Companies that integrate EMC expertise into their electric motor development at an early stage gain a competitive advantage.
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