What is BS EN 60940- Electromagnetic interference suppression about?
BS EN 60940 is a safety standard on the application of capacitors, resistors, inductors, and complete filter units for electromagnetic interference suppression.
BS EN 60940 provides guidance applicable to information on the application of capacitors, resistors, inductors, and complete filter units for electromagnetic interference suppression.
The effectiveness of interference suppression is a function of the suppression component construction, mounting of the component in the machine or apparatus, the radiofrequency voltage spectrum generated by the machine or apparatus and of characteristics of the external circuit.
Who is BS EN 60940- Electromagnetic interference suppression for?
BS EN 60940 on the application of capacitors, resistors, inductors and complete filter units for electromagnetic interference suppression is relevant to:
- Manufacturers of capacitors, resistors, inductors and complete filter units
- Manufacturers of electrical machines, equipment, and apparatus
- Electromagnetic engineers
- Electrical engineers
- EMI engineers and technicians
- Electricians
- Testing authorities
Why should you use BS EN 60940- Electromagnetic interference suppression?
Electromagnetic interference, EMI, is any electromagnetic emission or any electric or electronic disturbance which causes an undesirable response, malfunctioning, or degradation in the performance of electrical equipment.
Electrical machines and apparatus may generate electromagnetic interferences (EMI) which are fed back into power supply mains. These electromagnetic interferences may be picked up by apparatus connected to or placed close to the same power system up to a certain distance from the machine or apparatus. EMI or RFI propagate through conduction over signal and power lines and through radiation in free space. BS EN 60940 assists with the limits of interference.
Radio interference suppression capacitors are divided into the following groups:
- Two-terminal capacitors, which can be connected to the machine, apparatus, or supply system to provide for either symmetrical or asymmetrical interference suppression
- Combinations of capacitors (either combination of separate capacitors or multi-section capacitor the sections of which may be connected in a certain manner), which can be connected to the machine, apparatus, or supply system to provide for both symmetrical and asymmetrical interference suppression
- Lead-through capacitors (asymmetrical or symmetrical) or combinations thereof, in which one or more sets of terminations are interconnected by means of a conductor intended to carry the power supply current. These capacitors are especially suited to provide interference suppression at the place where the supply system phases through a shielded housing
- Resistor-capacitor combinations consist of a capacitor with the capacitor utilizing the resistance of the capacitor electrodes. RC combinations are often used for the suppression of switching surges
Radio interference suppression inductors are divided into the following groups:
- Simple coils either with an air core or wound on a magnetic core. The UHF choke is an example of this type of inductor
- Coils wound on a closed magnetic core. These inductors may have two or more coils wound on the same core, which is often of ferrite material. The windings are often arranged so that there is no resultant magnetization induced in the core due to the power current when the inductor is known as current-compensated
- Inductance, at high frequencies, may be obtained for suppression purposes by threading ferrite beads onto lead wires
- Some core materials, especially ferrite materials, can be designed to introduce high resistive losses at VHF and UHF, adding to the suppression obtained by the inductance of the coil
Radio interference filters are construed from inductors and capacitors, sometimes with the addition of resistors, varistors, etc. Two diverse types are distinguished:
- Filters constructed from approved components either as an unprotected assembly or with a simple protective casing. The approval testing of these filters can be simplified since it is not necessary to repeat the tests already carried out on the components
- Filters constructed from components that are not approved, or which are constructed from capacitive, inductive, or resistive elements all contained in a housing. For such filters, it is necessary to carry out a full range of qualification approval tests
Overall, BS EN 60940 is useful as it provides guidance on the suppression that is often more effective if the electrical parts of the apparatus are completely in the metal shielding, asymmetrical interference suppression is usually effected by connecting a capacitor from each phase (or phase and neutral) to the shielding.
