Consistent and precise testing is crucial to the development of compliant EMC components

Consistent and precise testing is crucial to the development of compliant EMC componentsElectromagnetic compatibility (EMC) is an essential element of any electronics design, as electromagnetic interference (EMI) can disrupt electronic equipment and systems. Understanding how a component will function in the final application is key; however, the impact of different environments can change your test results.

We use the European Standard testing methodology EN 55017 to measure the suppression characteristics of passive EMC components, such as cores, chokes and filters, as all modules and single components can be considered to be a passive, low-pass filter. EN 55017 exactly describes approved measurement methods to ensure results are consistent, independent of the tester.

Testing to EN 55017 standards

Following the initial development and testing of a component, EN 55017 testing focuses on the functionality (damping of noise) of the component to ensure the design is compliant to your industry's or sector's standards. For example, attenuation measurements in differential mode, common mode and unsymmetrical mode, are taken over the full desired frequency range. These measurements are critical to establishing the performance of the design, but it requires both knowledge and experience to interpret the results, not least because of the influences of the input and output impedances. Attachment C of EN 55017 defines four different impedance systems; 50 to 50Ω, 75 to 75Ω, 0.1 to 100Ω and 100 to 0.1Ω. In the measurement praxis, a 50-50Ω impedance system is normally used.

Saturation in a common mode situation is seldom considered for standard components, but it has a detrimental impact on choke or filter performance. In some cases it can stop the design from functioning, so it is essential to test for this parameter.

At the Custom Services for Magnetic Components (CSfMC) team, our expert engineers use our regularly serviced and calibrated impedance analyser and vector analyser (network analyser) to test EMI components, by applying DC currents to analyse saturation behaviour for common mode noise created by parasitic effects.

The leakage current of EMI filter modules is a value that is difficult to define exactly. This parameter needs to be defined by the calculation of the input voltage and frequency, for example 250V and 50Hz. Test results and field operation does not exactly match, therefore it is best to measure leakage current directly during system integration and adjust the component design at this stage. The CSfMC team support this process with adjustments to prototypes, working directly with the customer.

  Consistent and precise testing is crucial to the development of compliant EMC components  

Keeping consistent results throughout production

When a component design is created with the functionality needed for a customer's specific application and environment, we must ensure that the properties are reproduced in series production. However, attenuation test methods are not used to check components during production, as the measurements are too complex to obtain in a time effective manner.

Instead, we batch test, checking that the components operate within a specific range for defined qualities. Attenuation properties for common mode chokes depend directly on the impedance which is tested as inductance. Upon entering production, values for this parameter will be defined at selected test conditions, such as frequency and AC and DC signal levels. The CSfMC team use LCR meters and automated testers to test components effectively and reliably in the supply chain.

Supporting your EMC needs

The CSfMC team have the expertise, knowledge and specialist equipment to test EMC components in a variety of circumstances. We offer total support throughout the design and production phases, testing the attenuation properties over a high-frequency range, according to the EN 55017, and designing the EMI filter (module or common mode choke) according to your interference spectrum.

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