Conducted emissions

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Conducted emissions are the effects in power quality that occur via electrical and magnetic coupling, electronic switch of semiconductor devices, which form a part of electromagnetic compatibility issues in electrical engineering. These affect the ability of all interconnected system devices in the electromagnetic environment, by restricting or limiting their intentional generation, propagation and reception of electromagnetic energy.

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Fig. 1. Conducted Emission propagation from Source to Receptor Conducted Emission propagation.png
Fig. 1. Conducted Emission propagation from Source to Receptor

Conducted emissions consist a part of electromagnetic interference in circuits that mainly create issues in delivered power quality, owing to interference caused by harmonics arising due to linear & non linear loads present in the electric system mainly due to increasing presence of switched mode power supply and other consumer electronics. Due to these aggregated interferences, [1] the delivered electric power quality from the mains electricity system affects the performance of electrical home appliances. These could include a decrease in lumen output of bulbs, flicker and poor heating of induction coil in kettles, and heating elements of other home appliances in every-day use.

Following the effects of conducted emissions, the electric power quality is classified separately in common AC mains and DC mains systems. Since alternating current technology has been well established, the parameters and the effects in power quality in AC are well established. [2] The parameter for measuring AC power quality is called is termed total harmonic distortion (%THD), and it measures the power quality of power supply for different voltage levels. Due to the recent developments in DC technology, the interconnections between DC and AC mains give rise to harmonic issues not previously experienced. Especially, the effects in DC power quality due to conducted emissions are not well understood. Moreover, the interconnections of AC and DC mains has given rise to further electromagnetic interference issues not previously known. Based on the current EMC standards, conducted emissions are measured from 150 kHz and 30 MHz, however there exists a gap in the electric power quality measured up to 2 kHz and the conducted emissions in the low frequency up to 150 kHz. The gap frequency range is termed Supraharmonics. [3]

Further, following the advancements in telecommunications engineering, the presence of electronic devices has gradually increased in the AC mains grid network towards having more semiconductor based switch devices, giving rise to further electromagnetic interference issues due to conducted emissions in the near and far electromagnetic environment. The electric grid progresses towards becoming increasingly nonlinear system and newer issues in power quality are being addressed.

Technically, conducted emissions may be described as noise in the electric current or voltage generated by the electrical appliance or its susceptibility to it. The main difference between signal noise and emissions is that noise exists in a finite energy signal while emission exists in a finite power signal. As noise in measuring circuits gets filtered out using filters, the emission must be filtered at the device under test at either the AC mains or the DC mains, depending on the device application. The emission source can exist from the source to the receptor and through the circuit where there is electron flow. Usually, the electrical appliance must be factory tested with standards for conducted emission, as the list of common EMC test standards denotes. Moreover, different manufacturers hold different versions of these standards as fit best to their appliances and warranty schemes.

Fig. 2. Conducted Emissions from a commercial DC buck converter Conducted Emissions from a commercial DC buck converter.jpg
Fig. 2. Conducted Emissions from a commercial DC buck converter

Conducted emissions in electric supply system could be described as non-linearity or deviations observed in electric parameters. In AC, the variations are observed in the harmonics, while in DC they are observed as non linearity observed in time-domain and unexpected frequency peaks in frequency domain. The effects of conducted emissions in power quality in AC mains are well established in IEC standards, particularly in IEC Std 519–2014. Further, conducted emissions in DC are from multiple sources including electronic devices, non linear loads and other rotating magnetic field devices. In electronic devices, these are mainly from the interactions in the RLC circuit and the switching frequency. When loads like motors and generators that have DC magnetic fields, the conducted emission are non linear and difficult to predict. Further, the effects of conducted emissions in DC power quality is not well understood and is being researched extensively.

Effects on electric power quality

Electric power quality in AC mains is well developed and established with empirical data gathered over a century. Many parameters exist to determine and calculate the harmonic along with the noise. Concerning DC mains, much of the DC technology research for electric power distribution was abandoned in the 1920s after it was decided that AC alternating systems were to be applied over large distances. However, due to recent developments in photovoltaic system rooftop solutions and lesser electronic conversion stages required between AC & DC, researchers are now considering DC to be used to supply power to household appliances at low voltage and extra-low voltage levels.

Harmonics in AC Mains

For alternating current technology has been well established in the modern world, the parameter for measuring conducted emissions is well understood and is called total harmonic distortion (%THD). It measures power quality of AC mains for different voltage levels as described in common EMC test standards. By definition, the AC harmonic is a multiple of the electrical quantity (voltage or current) at multiples of the fundamental frequency of the system, produced by the action of non-linear loads such as rectifier, lighting, or saturated magnetic devices. Harmonic frequencies in the power grid are a frequent cause of power quality problems and can result in increased heating in the equipment and conductors, misfiring in variable speed drives, and torque pulsations in motors. Depending on the frequency of the harmonics, the harmonic pollution is categorized in problems of electric power quality (frequency up to harmonic order 40), electromagnetic compatibility (frequency higher than 150 kHz), and low frequency compatibility (frequency between 2/3 kHz and 150 kHz).

Harmonics in DC Mains

Unlike AC, DC has no fundamental frequency or period and hence there cannot be a multiple of the fundamental frequency over which harmonics can be calculated. Further, the frequency range over which DC harmonics are calculated might not be the same as AC harmonics. Much of research covering DC harmonics suggest use of a percentage low frequency sinusoidal disturbance (%LFSD). [4] This quantity measures the deviations that the DC quantity (voltage or current) over a specified measurement window or an analysis window in a frequency range. The percentage of root of squared summations of these deviations gives a total %LFSD value, which is a near equivalent of the %THD value in AC systems. Further, the DC harmonics are being studied in two frequency bandwidth as per the interference observed empirically.

Fig. 3. Supraharmonics from DC buck converter Supaharmonics from DC buck converter.jpg
Fig. 3. Supraharmonics from DC buck converter

Other issues with power quality in DC mains are to do with frequency range for conducted emissions in the electromagnetic spectrum. In the range of 0–2 kHz, commonly termed as garbage band, [5] the DC harmonic quantity is calculated using an analogue of AC harmonics in frequency domain. However, as per the expected interactions between AC and DC systems and due to presence of power electronic devices and switched-mode power supply, the frequency range 2–150 kHz, recently termed as Supraharmonics [6] is being researched. It is primarily understood that due to the presence of electronic switching non-linear loads, the filter circuits tend to push emissions away into higher frequency bands.

This frequency bandwidth is in the range of 0–2 kHz and is equivalent to the same frequency range as AC harmonics. The name suggest that lower amount of conducted emissions are expected due to advancements in filters. It is widely accepted among researchers that the %LFSD value should be sufficient to address the DC harmonics and relate to the %THD in AC harmonics.

This frequency bandwidth is in the range of 2–150 kHz and is termed as Supraharmonics. [7] The frequency bandwidth was previously ignored and was considered as a gap between radiated emission and conducted emission. The current research suggest that much effort is being given to understand measurement methods for supraharmonic emissions in order to further standardize DC power quality to include short circuits, voltage variations and other factors as well.

As per Thais.M.Mendes et al., [8] the effects of Supraharmonic emissions are confined to neighboring devices and do not propagate over long distances. Defining the measurement window and analysis window is one of the appropriate way to standardize conducted emissions. Measurements as per IEC 61000-4-7, IEC 61000-4-30, IEC-61000-4-19 and other CISPR standards show that each method can be effective but have its own limitations. Further, as per M.Klattt et al. [9] measurement windows should be used in standardizing the framework for supraharmonic standards. Moreover, V.Khokhlov et al. [10] suggests that all the existing standards have limitations that can be overcome by combining time-based analysis with frequency domain analysis.

Related Research Articles

<span class="mw-page-title-main">Electromagnetic compatibility</span> Electrical engineering concept

Electromagnetic compatibility (EMC) is the ability of electrical equipment and systems to function acceptably in their electromagnetic environment, by limiting the unintentional generation, propagation and reception of electromagnetic energy which may cause unwanted effects such as electromagnetic interference (EMI) or even physical damage to operational equipment. The goal of EMC is the correct operation of different equipment in a common electromagnetic environment. It is also the name given to the associated branch of electrical engineering.

In electrical engineering, the power factor of an AC power system is defined as the ratio of the real power absorbed by the load to the apparent power flowing in the circuit. Real power is the average of the instantaneous product of voltage and current and represents the capacity of the electricity for performing work. Apparent power is the product of RMS current and voltage. Due to energy stored in the load and returned to the source, or due to a non-linear load that distorts the wave shape of the current drawn from the source, the apparent power may be greater than the real power, so more current flows in the circuit than would be required to transfer real power alone. A power factor magnitude of less than one indicates the voltage and current are not in phase, reducing the average product of the two. A negative power factor occurs when the device generates real power, which then flows back towards the source.

The total harmonic distortion is a measurement of the harmonic distortion present in a signal and is defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency. Distortion factor, a closely related term, is sometimes used as a synonym.

<span class="mw-page-title-main">Alternating current</span> Electric current that periodically reverses direction

Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time, in contrast to direct current (DC), which flows only in one direction. Alternating current is the form in which electric power is delivered to businesses and residences, and it is the form of electrical energy that consumers typically use when they plug kitchen appliances, televisions, fans and electric lamps into a wall socket. A common source of DC power is a battery cell in a flashlight. The abbreviations AC and DC are often used to mean simply alternating and direct, respectively, as when they modify current or voltage.

<span class="mw-page-title-main">Mains electricity</span> Type of lower-voltage electricity most commonly provided by utilities

Mains electricity or utility power, power grid, domestic power, and wall power, or, in some parts of Canada, hydro, is a general-purpose alternating-current (AC) electric power supply. It is the form of electrical power that is delivered to homes and businesses through the electric grid in many parts of the world. People use this electricity to power everyday items by plugging them into a wall outlet.

<span class="mw-page-title-main">Power supply</span> Electronic device that converts or regulates electric energy and supplies it to a load

A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As a result, power supplies are sometimes referred to as electric power converters. Some power supplies are separate standalone pieces of equipment, while others are built into the load appliances that they power. Examples of the latter include power supplies found in desktop computers and consumer electronics devices. Other functions that power supplies may perform include limiting the current drawn by the load to safe levels, shutting off the current in the event of an electrical fault, power conditioning to prevent electronic noise or voltage surges on the input from reaching the load, power-factor correction, and storing energy so it can continue to power the load in the event of a temporary interruption in the source power.

<span class="mw-page-title-main">Power inverter</span> Device that changes direct current (DC) to alternating current (AC)

A power inverter, inverter or invertor is a power electronic device or circuitry that changes direct current (DC) to alternating current (AC). The resulting AC frequency obtained depends on the particular device employed. Inverters do the opposite of rectifiers which were originally large electromechanical devices converting AC to DC.

<span class="mw-page-title-main">Switched-mode power supply</span> Power supply with switching regulator

A switched-mode power supply is an electronic power supply that incorporates a switching regulator to convert electrical power efficiently.

A DC-to-DC converter is an electronic circuit or electromechanical device that converts a source of direct current (DC) from one voltage level to another. It is a type of electric power converter. Power levels range from very low to very high.

<span class="mw-page-title-main">Motor–generator</span> Device for converting electrical power to another form

A motor–generator is a device for converting electrical power to another form. Motor–generator sets are used to convert frequency, voltage, or phase of power. They may also be used to isolate electrical loads from the electrical power supply line. Large motor–generators were widely used to convert industrial amounts of power while smaller motor–generators were used to convert battery power to higher DC voltages.

<span class="mw-page-title-main">AC adapter</span> Type of external power supply

An AC adapter or AC/DC adapter is a type of external power supply, often enclosed in a case similar to an AC plug. Other common names include wall wart, power brick, wall charger, and power adapter. Adapters for battery-powered equipment may be described as chargers or rechargers. AC adapters are used with electrical devices that require power but do not contain internal components to derive the required voltage and power from mains power. The internal circuitry of an external power supply is very similar to the design that would be used for a built-in or internal supply.

Electric power quality is the degree to which the voltage, frequency, and waveform of a power supply system conform to established specifications. Good power quality can be defined as a steady supply voltage that stays within the prescribed range, steady AC frequency close to the rated value, and smooth voltage curve waveform. In general, it is useful to consider power quality as the compatibility between what comes out of an electric outlet and the load that is plugged into it. The term is used to describe electric power that drives an electrical load and the load's ability to function properly. Without the proper power, an electrical device may malfunction, fail prematurely or not operate at all. There are many ways in which electric power can be of poor quality, and many more causes of such poor quality power.

<span class="mw-page-title-main">Variable-frequency drive</span> Type of adjustable-speed drive

A variable-frequency drive, variable-speed drives, AC drives, micro drives, inverter drives, or drives) is a type of AC motor drive that controls speed and torque by varying the frequency of the input electricity. Depending on its topology, it controls the associated voltage or current variation.

Mains hum, electric hum, cycle hum, or power line hum is a sound associated with alternating current which is twice the frequency of the mains electricity. The fundamental frequency of this sound is usually double that of fundamental 50/60 Hz, i.e. 100/120 Hz, depending on the local power-line frequency. The sound often has heavy harmonic content above 50/60 Hz. Because of the presence of mains current in mains-powered audio equipment as well as ubiquitous AC electromagnetic fields from nearby appliances and wiring, 50/60 Hz electrical noise can get into audio systems, and is heard as mains hum from their speakers. Mains hum may also be heard coming from powerful electric power grid equipment such as utility transformers, caused by mechanical vibrations induced by magnetostriction in magnetic core. Onboard aircraft the frequency heard is often higher pitched, due to the use of 400 Hz AC power in these settings because 400 Hz transformers are much smaller and lighter.

This is an alphabetical list of articles pertaining specifically to electrical and electronics engineering. For a thematic list, please see List of electrical engineering topics. For a broad overview of engineering, see List of engineering topics. For biographies, see List of engineers.

IEC 61000-3-2Electromagnetic compatibility (EMC) – Part 3-2: Limits – Limits for harmonic current emissions is an international standard that limits mains voltage distortion by prescribing the maximum value for harmonic currents from the second harmonic up to and including the 40th harmonic current. IEC 61000-3-2 applies to equipment with a rated current up to 16 A – for equipment above 16 A see IEC 61000-3-12.

<span class="mw-page-title-main">Low-frequency electromagnetic compatibility</span>

Low-frequency electromagnetic compatibility is a specific field in the domain of electromagnetic compatibility (EMC) and power quality (PQ), which deals with electromagnetic interference phenomena in the frequency range between 2 kHz and 150 kHz. It is a special frequency range because it does not fit in the PQ problems, with range of up to 2 kHz, where relative levels of voltage and current can have massive impact on efficiency and integrity of electric systems, and neither in the conducted EMC range, which starts at 150 kHz and influences mainly informational systems, and already too far from radiated EMC range, which starts at 30 MHz and goes up to 1 GHz.

References

  1. ↑ Espín-Delgado, Ángela; Rönnberg, Sarah; Busatto, Tatiano; Ravindran, Vineetha; Bollen, Math (1 July 2020). "Summation law for supraharmonic currents (2-150 kHz) in low-voltage installations". Electric Power Systems Research . 184: 106325. doi:10.1016/j.epsr.2020.106325. S2CID   216222427.
  2. ↑ Ewald Fuchs, Mohammad Masoum (14 July 2015). Power quality in power systems and electrical machines (2nd ed.). Academic Press/Elsevier. ISBN   9780128009888.
  3. ↑ Bollen, Math; Meyer, Jan; Amaris, Hortensia; Blanco, Ana Maria; Gil de Castro, Aurora; Desmet, Jan; Klatt, Matthias; Kocewiak, Łukasz; Rönnberg, Sarah; Yang, Kai (May 2014). "Future work on harmonics - some expert opinions Part I - wind and solar power". 2014 16th International Conference on Harmonics and Quality of Power (ICHQP). pp. 904–908. doi:10.1109/ICHQP.2014.6842870. hdl: 1854/LU-4411980 . ISBN   978-1-4673-6487-4. S2CID   40319453.
  4. ↑ Margo, M. Caserza (12 March 2007). "Definition of Power Quality Indices for DC Low Voltage Distribution Networks". 2006 IEEE Instrumentation and Measurement Technology Conference Proceedings.
  5. ↑ Thomas, David (2013). "Conducted emissions in distribution systems (1 kHz–1 MHz)". IEEE Electromagnetic Compatibility Magazine. 2 (2): 101–104. doi:10.1109/MEMC.2013.6550941. S2CID   23396866 . Retrieved 26 June 2020.
  6. ↑ Novitskiy, Alexander; Schlegel, Steffen; Westermann, Dirk (May 2018). "Analysis of supraharmonic propagation in a MV electrical network". 2018 19th International Scientific Conference on Electric Power Engineering (EPE). pp. 1–6. doi:10.1109/EPE.2018.8396041. ISBN   978-1-5386-4612-0. S2CID   49541155.
  7. ↑ Bollen, Math; Meyer, Jan; Amaris, Hortensia; Blanco, Ana Maria; Gil de Castro, Aurora; Desmet, Jan; Klatt, Matthias; Kocewiak, Łukasz; Rönnberg, Sarah; Yang, Kai (May 2014). "Future work on harmonics - some expert opinions Part I - wind and solar power". 2014 16th International Conference on Harmonics and Quality of Power (ICHQP). pp. 904–908. doi:10.1109/ICHQP.2014.6842870. hdl: 1854/LU-4411980 . ISBN   978-1-4673-6487-4. S2CID   40319453.
  8. ↑ Mendes, Thais M.; Duque, Carlos A.; Manso da Silva, Leandro R.; Ferreira, Danton D.; Meyer, Jan; Ribeiro, Paulo F. (1 June 2020). "Comparative analysis of the measurement methods for the supraharmonic range". International Journal of Electrical Power & Energy Systems. 118: 105801. doi:10.1016/j.ijepes.2019.105801. S2CID   213808616.
  9. ↑ Klatt, Matthias; Meyer, Jan; Schegner, Peter (May 2014). "Comparison of measurement methods for the frequency range of 2 KHZ to 150 KHZ". 2014 16th International Conference on Harmonics and Quality of Power (ICHQP). pp. 818–822. doi:10.1109/ICHQP.2014.6842791. ISBN   978-1-4673-6487-4. S2CID   10197994.
  10. ↑ Khokhlov, Victor; Meyer, Jan; Grevener, Anne; Busatto, Tatiano; Rönnberg, Sarah (2020). "Comparison of Measurement Methods for the Frequency Range 2–150 kHz (Supraharmonics) Based on the Present Standards Framework". IEEE Access. 8: 77618–77630. doi: 10.1109/ACCESS.2020.2987996 . S2CID   218564904.
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