Interference Spreading
© Siemens AG, 2004. All rights reserved
3-16 EMC Installation Guideline – Planning Guide (EMV) – 03.2004 Edition
3.1 Interference sources
The initiator of the interference is described as the interference source. The noise
levels generated by the interference sources or their effects must be eliminated or
at least dampened by appropriate measures.
Table 3-1 Typical interference sources and their effects on interference sinks
Interference source
Interference generated
by…
Effect
Switched inductors such as e.g.
contactors, relays, electronic valves
- Contacts
- Coils
- System disturbances
- Electromagnetic fields
- Magnetic fields
Electrical motors - Collectors
- Coils
- Electromagnetic fields
- Magnetic fields
Sparking machines such as
e. g. electrical welding equipment,
electrical discharge machines
- Contacts
- Transformers
- Electromagnetic fields
- System disturbances
- Compensating currents
- Magnetic fields
Power supply units - Circuits
- Switching components
- Electromagnetic fields
- System disturbances
High-frequency appliances - Circuits - Electromagnetic fields
Transmitters - Antennas - Electromagnetic fields
Earth or reference potential
differences
- Voltage differences - Compensating currents
Operator - Discharges of static
electricity
- Electrical discharge currents
- Electrical fields
Power lines - Current flows
- Fuse cases
- Power break-ins, power
overvoltages
- Electrical and magnetic fields
Transmission lines - Voltage differences
- Corona discharges
- Electromagnetic fields
- Electrical fields
Current converters, power electronics - Circuits - Overvoltages
- Compensating currents
3.2 Interference sinks
An interference sink is an electrical device, whose function can be influenced by
interference sizes.
Table 3-2 Typical interference sinks and their reaction on interferences
Interference sinks are sensitive against… Reaction
Microprocessor-controlled
systems, bus systems
Pulse-shaped noise levels (e.g.
switching operations) and
electromagnetic fields
Sporadic processor shutdown,
transmission errors
Analog circuits Low-frequency noise levels (e.g.
potential differences)
Superimposition of the effective signal
on the noise level (e.g. 50 Hz hum on
setpoint)
Electron beam monitors low-frequency magnetic fields
(> 1.5 A/m)
Flickering screen or image, colour
distortion
Telephones Mains second harmonics Whistling is audible
Fax machines, power
supply units
Mains second harmonics Fuse case or defect in the power supply
unit, whistling is audible
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