EMC is short for Electro Magnetic Compatibility. Any electrical conductor exposes a magnetic field when a current flows. This magnetic field can induce a current in another nearby conductor, which can potentially be misread by the equipment and affect performance. It may even cause malfunctions and dangerous actions by the equipment.
To avoid this, different phenomena that often occur in the real world have been described. One is radiated immunity: the local radio broadcast antenna emits a signal, which a radio receives via its antenna. However, any other equipment that has a conductor, like supply cables or sensor cables, will also be exposed to the radio signal, and these cables will act as antennas. If the equipment or appliance is not immune to these radio signals, it may misread them as something it should react to, leading to a malfunction.
The performance of the equipment when exposed is described in a performance criterion. In the above example with a radio transmitter, the signal is always present. The radio stations are active day in and day out. Therefore, equipment must also be able to work correctly with such a signal present, hence performance criterion A.
Other disturbances occur only temporarily. A bouncing relay contact emits burst transients, but this occurs only when the contact is opening or closing, not when it is stable (on or off). If other equipment reacts to such transients, it must return to normal performance by itself when the transient has passed. This is criterion B.
Proper grounding and connections are key to effective EMC performance.
Ensuring proper installation for optimal performance
Just as importantly, the equipment must not expose other equipment to the same kind of transient if it has a relay inside. There is a margin between the allowed emissions from appliances and the immunity of the same appliances. However, this does not prevent disturbances if the appliances are not installed or used correctly. Many electricians have experienced faults in production equipment, finding everything connected correctly and working as intended when tested.
But when looking at the equipment with EMC eyes, potential improvements may be visible. Are all metal parts connected to ground? Screws and bearings are poor electrical connections, and a standard 1.5 mm² PE wire does not work at high frequencies. Metal parts must be interconnected with a wide strap, which should not be electrically connected via the mounting screw. The screw keeps the strap in place, but the electrical connection must be directly from the metal part to the strap; that is, no insulation in between (e.g., paint or foil).
What is EMC?
Product Manager Michael Vedele Sørensen, tells about EMC and how we at Eltwin work with it every day.
Another often-seen mistake is the positioning of the EMC filter. If the cables or wires from the EMC filter are placed in the same cable tray or path as the cable to the filter, then high-frequency electrical noise will couple between the cables, and the filter will be bypassed, thus not functioning as intended.
When considering the requirements in the harmonized EN standards, these are minimum requirements to presume compliance with CE requirements. This is not enough to provide a quality product, so Eltwin uses enhanced requirements to deliver quality products.
Enhanced requirements not only add amplitude to the known phenomena but also include other relevant phenomena while considering the required performance criteria. Ultimately, it is about understanding how the product is intended to be installed and used and what expectations users have regarding functionality, robustness, and lifespan.
At Eltwin, we work with EMC every day. We have invested in our own laboratory, and our staff is trained and participates in technology forums regularly. Our products are used across a range of applications, from household and industrial use to marine and automotive use.
