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Filter Design Techniques and Design Examples
Published in Richard Lee Ozenbaugh, Timothy M. Pullen, EMI Filter Design, 2017
Richard Lee Ozenbaugh, Timothy M. Pullen
There are numerous techniques for designing filters. Some are based upon formal methods using numerical analysis; many others are based upon individual process, rules of thumb, and trial and error. Typically, EMI filters are used to reduce conducted emissions to an acceptable level so that a given test specification may be met. EMI filters may also be used to limit inrush current and suppress voltage transients caused by lightning and line transients. The specifications for the allowable interference are generally driven by the power circuit specification. The most common specifications include MIL-STD-461 for military applications, while CISPR and DO-160 are used for commercial applications. Many other EMI specifications also exist. This chapter provides technical discussion and analysis, including techniques that may be employed in the design of EMI filters that reduce conducted interference. The design of the input filter is slightly more critical when the power circuit topology is a regulated switching circuit such as a PWM power supply or a motor controller, etc., rather than a linear circuit. This is primarily due to the incremental negative input resistance that is a phenomenon of a switching circuit. This factor alone drives specific needs for the filter to ensure system stability and is presented in this chapter. The EMI filter design examples in this chapter assume that the load is a PWM power converter and not a linear load regulator.
EMI and EMC Control, Case Studies, EMC Prediction Techniques, and Computational Electromagnetic Modeling
Published in David A. Weston, Electromagnetic Compatibility, 2017
Conducted emissions are those signals that appear on cables at other than required operating frequencies. These emissions can either be continuous (CW) or transient in nature. From experience, systems utilizing circuitry that generates emissions rich in harmonic content (i.e., DC-DC converters) or that switch currents are almost certain to fail the requirements. This implies that some type of EMI reduction technique be included in the original design to reduce conducted emissions.
Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
Conducted emissions are generated inside electrical or electronic equipment and may be transmitted outward through the equipment’s data input or output lines, its control leads, or its power conductors. Conducted emissions may cause an EMI problem between equipment that generates useful emissions and other equipment with low immunity to those same emissions.
Supraharmonics reduction in LED drivers via random pulse-position modulation
Published in International Journal of Electronics, 2018
Joaquin Garrido-Zafra, Antonio Moreno-Munoz, Aurora Gil-De-Castro, Manuel A. Ortiz-López, Tomás Morales
Concerns about conducted emissions were originally in the range of 450–30 MHz. With enough foresight, that range was extended down to 150 kHz, and afterward further to 2 kHz. PQ harmonics traditionally range from frequencies just above DC to 3 kHz (in IEEE-519) or 9 kHz (in IEC). There are considerable on-going activities within IEC (both SC 77A and SC 205A), CENELEC and IEEE to develop standards, for example compatibility levels, limits and adequate test methods, covering this frequency range in voltage. However, setting current limits on the total installation (as in IEEE Std. 519) and setting current limits on individual devices (as in IEC 61,000–3–2) would be very difficult, as emission in the supraharmonic range behaves differently to that at low frequency. An updated summary of standardisation in this supraharmonic range is done in Rönnberg et al. (2017).