Emi Project Report
Emi Project Report
Emi Project Report
The Electromagnetic Interference (EMI) is an unwanted and intolerable to system and sub system of all Electrical, Electronic and Electromechanical devices. Now, this has become dangerous concern to us because of development of Electrical, Electronic equipment. Our day by day usage of electric or electronic equipment for industry, entertainment, domestic, medical and medical is increasing at pace rate. All the above the Application development are causing problem to created Electromagnetic Interference. The main and prime factor is control the EMI level as per the application standard is most essential for living organism on earth to live in balanced condition. This mini project contains some of the case study of Electromagnetic Interference and its control methods.
Introduction:
The use of electronic equipment is increasing day by day. Each electronic product needs specific circuit & frequency for the operation of the products. Most of electronic products are sensitive to radiated frequency & generates emission to the environment & power line. Due to the use of electronic product in every walk of life, the electromagnetic pollution is increasing day by day, which results in the performance of products by this pollution. Now a days most of electronic products uses the digital technology for the operation. Digital as well as analog circuits are sensitive to radiated field and as well as conducted noise. These noises affect the performance of products like disturbance in TV picture by running grinder, disturbance in telephone line, resetting & hanging of computer due to power line disturbances etc. The operation of equipment is effected by this pollution. It is desired that all products shall work satisfactorily without affecting other & getting affected to others. In view of these, the emission &immunity tests are performed. Product specification described the limit of emission as well immunity. To verify that a specific products will work satisfactory or not on a specific EM environment, the immunity testing are performed by creating the specific environment & verifying the same. Similarly products introduce certain noise/emission in the environment and as well as in power line. Emissions are of two types, Conducted & Radiated. Conducted emission is propagated by conducting wires etc. However radiated does not need any hard connection & these are radiated through radiation. Considerations of EMI are crucial in the design of circuits and equipment for use in electrical power systems, computers, telecommunications, controls, industrial, and
medical instrumentation, transportation electronics, military equipment, information technology products, consumer electronics, and home electrical appliances. It is well recognized that EMI aspects must be addressed at the beginning in the design of circuits, including printed circuit boards and packaging of equipment and systems. EMI problems often cause delays in providing satisfactory field operation of systems. Compliances practices are used to comply the emission and immunity requirements. Various techniques are followed to improve the performance in respect of EMI such as PCB design, grounding, filtering, shielding and bonding practices.
There are many forms of electromagnetic interference, EMI that can affect circuits and prevent them from working in the way that was intended. This EMI or radio frequency interference, RFI as it is sometimes called can arise in a number of ways, although in an ideal world it should not be present. EMI - electromagnetic interference can arise from many sources, being either man made or natural. It can also have a variety of characteristics dependent upon its source and the nature of the mechanism giving rise to the interference. By the very name of interference given to it, EMI is an unwanted signal at the signal receiver, and in general methods are sought to reduce the level of the interference. Types of EMI - Electromagnetic Interference EMI - Electromagnetic Interference can arise in many ways and from a number of sources. The different types of EMI can be categorized in a number of ways. One way of categorizing the type of EMI is by the way it was created: Man-made EMI: This type of EMI generally arises from other electronics circuits, although some EMI can arise from switching of large currents, etc. Naturally occurring EMI: This type of EMI can arise from many sources cosmic noise as well as lightning and other atmospheric types of noise all contribute. Another method of categorizing the type of EMI is by its duration: Continuous interference: This type of EMI generally arises from a source such as a circuit that is emitting a continuous signal. However background noise, which is continuous may be created in a number of ways, either manmade or naturally occurring. Impulse noise: Again, this type of EMI may be man-made or naturally occurring. Lightning, ESD, and switching systems all contribute to impulse noise which is a form of EMI. It is also possible to categorize the different types of EMI by their bandwidth. Narrowband: Typically this form of EMI is likely to be a single carrier source possibly generated by an oscillator of some form. Another form of narrowband EMI is the spurious signals caused by intermodulation and other forms of distortion in a transmitter such as a mobile phone of Wi-Fi router. These spurious signals will appear at different points in the spectrum and may cause interference to another user of the radio spectrum. As such these spurious signals must be kept within tight limits.
Broadband: There are many forms of broadband noise which can be experienced. It can arise from a great variety of sources. Man-made broadband interference can arise from sources such as arc welders where a spark is continuously generated. Naturally occurring broadband noise can be experienced from the Sun - it can cause sun-outs for satellite television systems when the Sun appears behind the satellite and noise can mask the wanted satellite signal. Fortunately these episodes only last for a few minutes.
EMI coupling mechanisms There are many ways in which the electromagnetic interference can be coupled from the source to the receiver. Understanding which coupling method brings the interference to the receiver is key to being able to address the problem. Radiated: This type of EMI coupling is probably the most obvious. It is the type of EMI coupling that is normally experienced when the source and victim are separated by a large distance - typically more than a wavelength. The source radiates a signal which may be wanted or unwanted, and the victim receives it in a way that disrupts its performance. Conducted : Conducted emissions occur as the name implies when there is a conduction route along which the signals can travel. This may be along power cables or other interconnection cabling. The conduction may be in one of two modes:
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Common mode: This type of EMI coupling occurs when the noise appears in the same phase on the two conductors, e.g. out and return for signals, or +ve and -ve for power cables. Differential mode: This occurs when the noise is out of phase on the two conductors.
The filtering techniques required will vary according to the type of EMI coupling experienced. For common mode lines are filtered together. For differential mode they may be filtered together. Inductive coupling: What is normally termed inductive coupling can be one of two forms, namely capacitive coupling and magnetic induction. Capacitive coupling : This occurs when a changing voltage from the source capacitive transfers a charge to the victim circuitry. Magnetic coupling: This type of EMI coupling exists when a varying magnetic field exists between the source and victim - typically two conductors may run close together (less than apart). This induces a current in the victim circuitry, thereby transferring the signal from source to victim.
Electromagnetic Radiation: Electromagnetic radiation (EM radiation or EMR) is a form of energy emitted and absorbed by charged particles which exhibits wave-like behavior as it travels through space. EMR has both electric and magnetic field components, which stand in a fixed ratio of intensity to each other, and which oscillate in phase perpendicular to each other and perpendicular to the direction of energy and wave propagation. In a vacuum, electromagnetic radiation propagates at a characteristic speed, the speed of light. Electromagnetic radiation is a particular form of the more general electromagnetic field(EM field), which is produced by moving charges. Electromagnetic radiation is associated with EM fields that are far enough away from the moving charges that produced them that absorption of the EM radiation no longer affects the behavior of these moving charges. These two types or behaviors of EM field are sometimes referred to as the near and far field. In this language, EMR is merely another name for the far-field. Charges and currents directly produce the near-field. However, charges and currents produce EMR only indirectlyrather, in EMR, both the magnetic and electric fields are associated with changes in the other type of field, not directly by charges and currents. This close relationship assures that the electric and magnetic fields in EMR exist in a constant ratio of strengths to each other, and also to be found in phase, with maxima and nodes in each found at the same places in space. Electro magnetic radiation carries energysometimes called radiant energythrough space continuously away from the source (this is not true of the nearfield part of the EM field). EMR also carries both momentum and angular momentum. These properties may all be imparted to matter with which it interacts. EMR is produced from other types of energy when created, and it is converted to other types of energy when it is destroyed. The photon is the quantum of the electromagnetic interaction, and is the basic "unit" or constituent of all forms of EMR. The quantum nature of light becomes more apparent at high frequencies (or high photon energy). Such photons behave more like particles than lower-frequency photons do.
The energy of the electromagnetic radiation is proportional to its frequency. The greater the frequency of the wave greater their energy.
Electromagnetic radiation is classified according to the frequency of its wave. Electromagnetic spectrum,in order of increasing frequency and decreasing wave length , consists of radio waves, microwaves, infrared radiation, visible light ,X-ray and gamma rays. The types of electromagnetic radiation are broadly classified into the following classes:[3] 1. 2. 3. 4. 5. 6. 7. Gamma radiation(>exa Hz) X-ray radiation(30 peta Hz- 30 exa Hz) Ultraviolet radiation(7.5 x 10^14Hz 3x 10^16 Hz) Visible radiation(490- 700 THz) Infrared radiation(1-400THz) Microwave radiation(300mHz-300GHz) Radio waves(3KHz-300GHz)
NATURE OF ELECTROMAGNETIC FIELD: Electropollution is basically the invisible electromagnetic energies emitted from various objects which rely on electricity to operate. Devices that utilize electricity often emanate electropollution. Electromagnetic fields are invisible and cannot be seen or smelled. The latter waves are detectable by a special device like Smart field meter or radiation monitors, which detects the waves as they emanate from electrically charged objects. These waves are considered dangerous in many instances and have been associated with a number of health concerns and issues. Differences in voltage are what causes variances in electromagnetic fields are which emanate from electricity charged objects. Even if the device has no power flowing to it, an electromagnetic field can be generated from device. The more that one is distanced from original source , which emanates the EMF waves, the better. Distances weaken the electromagnetic strength. Electromagnetic radiation has dual nature ,as its exhibits Wave properties Particulate (photon) properties Wave nature of radiation: Radiation can be thought of as a traveling tansverse wave. The electric and magnetic fields oscillate in the x-y plane and perpendicular to the direction of propagation z-axis. As a transverse wave, EM radiation can be polarized. Polarization is the distribution of the electric field in the plane normal to propagation direction. Waves are characterized by frequency, wavelength, speed and phase. Particulate nature of radiation Radiation can be also described in terms of particles energy, called photons. =hv= hc/ =hcv where h=planks constant =6.625x10^-34js
ELECTRO POLLUTION
Definition: Non ionizing electromagnetic radiation propagated through the atmosphere by broadcast towers, radar installation, and microwave appliances, and the magnetic fields surrounding electrical appliances and power lines, which is believed to have polluting effect on people and the environment. It is also called as Electro smog. Electropollution is a term that describes our increasing exposure to harmful invisible electronic frequencies harnessed by man in our modern world. Electronic frequency can be divided into these basic groups: Extremely Low Frequency (ELF): Power lines. Radio Frequency (RF): Radio and TV signals, microwaves and wireless devices. Intermediate Frequencies: Dirty electricity emitted by appliances, Electric circuits, etc. High Frequency: lionizing radiation, X-rays and CAT scans, which have been proven to cause cancer.
Intermediate Frequencies:
Intermediate frequencies are in the frame of this report, defined as frequencies between 300 Hz and 100 KHz. They involved two different mechanisms, namely induced currents and dielectric absorption. The frequency limit when one predominates over the other not precisely defined. Existence of effects depends upon two
superimposed phenomenon absorption of the external field in the organism at the macroscopic level and the stimulation of biological effects by the penetrating fields.
Compact Fluorescent Light bulbs (CFL) Hair Dryers Computers or TVs etc.,
Power Lines:
EMF is commonly associated with power lines. A person standing directly under a high-voltage transmission line may feel a mild shock when touching something that conducts electricity. These sensations are caused by the magnetic fields from the high-voltage electricity in the lines. They occur only at close range because the electric fields rapidly become weaker as the distance from the line increases. The power transmission lines, you house electricity and radio/microwave transmissions create a subliminal state of constant stress that over time degrades the immune system. A wide range of studies has documented the debilitating effects of this electro-pollution induced stress on the immune system. Manmade EMFs also paralyze the bodys electrically based healing systems. Many people lines and potential health effects is inconclusive. Despite more than two decades of research to determine whether elevated. EMF exposure, principally to magnetic fields, is related to an increased risk of childhood leukemia, there is still no definitive answer. Some scientists are coming to the conclusion that power line electromagnetic fields should be classified as a probable human carcinogen.