RCDD CHAPTER 2 ELECTROMAGNETIC COMPATIBILITY EXAM QUESTIONS AND ANSWERS

1. Light 2. Radio Waves 3. Microwaves 4. IR Radiation (IR) 5. Ultraviolet rays 6. X-rays 7. Gama Rays Electromagnetic Spectrum 1. Source 2. Susceptible Device 3. Coupling Path Three essential elements to any EMC Problem Conducted coupling may effect electronic devices through Input signal lines, output signal lines, Utility or premise electrical power distribution. Internal EMI sources are typically Electrical power supplies Electrical power cables Rectifiers Oscillators Digital clocks Common-mode signaling (CM) Long term or short term variations in voltage (swells, sags or under-voltages) Cathode Ray Tube Susceptible to RFI in the enviroment A device's EMC Its value is relative to the environment in which it operates EMC Electromagnetic Compatibility EMC aims to ensure..... That items or equipment will not interfere or prevent each other's correct operation through emission and absorption of EMI EMI laws explained... Basic laws of Physics EMI Cause A Circuit EMI is... Man made or Naturally occurring Natural sources EMI Atmospheric Electricity Cosmic Radiation or geomagnetism disturbance Man made sources of EMI Electrical Power Communications Electronics Relay Communications Susceptibility of Cables to EMI Improper Shielding, Filtering, Bonding and grounding of cable shields and equiptment ESD Electrostatic Discharge Three types of electrostatic discharge Discharge through a spark in the air Radiated effects of ESD Contact Discharge CM Common Mode DM Differential Mode NFPA 780 Standard for the Installation of Lightning Protection Systems Ground Loop Describes 2 parallel paths that have identical conductive terminations to two separate grounding (earthing) references Ground loops can be..... A source of EMI Lower Frequency's = Power Higher Frequency's = Data EMI mitigation technique Cable shielding Cable twists absorb the majority of EMI effects Lower Frequencies Cable shield absorbs the electromagnetic waves Higher Frequencies Cable shield effectiveness varies with the: Operating frequency Type, thickness, and geometry of the shielding Type and quality of the shield terminations Method of grounding (earthing) the shield Three major components of electromagnetically induced interference problem relating to telephone transmission facilities placed in a joint tunnel with an electrical power system are: Induced electromagnetic fields from electrical power system. Coupling between electrical power and telecommunications systems The susceptibility of the telecommunications system The potential difference between 2 grounds shall be no more than : 1.0V rms to avoid problems with conductive ground loops Add or Remove Terms