Series-parallel filters

In an HT system, either the star is not grounded or it is a delta-connected system and hence the third harmonic is mostly absent, while the content of the. second harmonic nuiy be too small to be of any significance. For this purpose, where harmonic analysis is not possible, or for a new installation where the content of harmonies is not known, it is common practice to use a series reactor of 6% of the reactive value of the capacitors installed. This will suppress most of the harmonics by making the circuit inductive, up to almost the fourth harmonic, as derived subsequently. Where, however, second harmonics are significant, the circuit may be tuned for just below the second harmonic. To arrive at a more accurate choice of filters, it is better to conduct a harmonic analysis of the system through a harmonic analyser and ascertain the actual harmonic quantities and their magnitudes present in the system, and provide a correct series or parallel filter-circuits for each harmonic. 

Figure 3.14 Schroeder s reverberator consisting of a parallel comb filter and a series allpass filter [Schroeder, 1962],...

Schroeder proposed a reverberator consisting of parallel comb filters and series allpass filters [Schroeder, 1962], shown in figure 3.14. The delays of the comb filters are chosen such that the ratio of largest to smallest is about 1.5 (Schroeder suggested... 

Harmonic filters are broadly classified into passive and active filters. Passive filters, as the name implies, use passive components such as resistors, inductors, and capacitors. A combination of passive components is tuned to the harmonic frequency that is to be filtered. Figure 4.22 is a typical series-tuned filter. Here the values of the inductor and the capacitor are chosen to present a low impedance to the harmonic frequency that is to be filtered out. Due to the lower impedance of the filter in comparison to the impedance of the source, the harmonic frequency current will circulate between the load and the filter. This keeps the harmonic current of the desired frequency away from the source and other loads in the power system. If other harmonic frequencies are to be filtered out, additional tuned filters are applied in parallel. Applications such as arc furnaces require multiple harmonic filters, as they generate large quantities of harmonic currents at several frequencies. 

Applying harmonic filters requires careful consideration. Series-tuned filters appear to be of low impedance to harmonic currents but they also form a parallel resonance circuit with the source impedance. In some instances, a situation can be created that is worse than the condition being corrected. It is imperative that computer simulations of the entire power system be performed prior to applying harmonic filters. As a first step in the computer simulation, the power system is modeled to indicate the locations of the harmonic sources, then hypothetical harmonic filters are placed in the model and the response of the power system to the filter is examined. If unacceptable results are obtained, the location and values of the filter parameters are changed until the results are satisfactory. When applying harmonic filters, the units are almost never tuned to the exact harmonic frequency. For example, the 5th harmonic frequency may be designed for resonance at the 4.7th harmonic frequency. 

In either version, cells of the bipolar type assembled to batteries of the filter-press t5q)e can be used. The version with circulating electrolyte is also feasible for building monopolar ( jai -type) cells that are cheaper than bipolar types (as they do not require expensive bipolar plates) and offer a highly flexible series-parallel switching within the battery to accommodate specific user needs. 

Chapter 2 contains detailed descriptions of the Zone 1 and 2A portions of the ventilation system. Ventilation system ducting provides the necessary confinement pathway during normal ventilation system operation to ensure filtration of exhaust gases prior to atmospheric release. The Zone 1 ventilation exhaust system contains redundant series-parallel charcoal filter banks located in the MER. The Zone 2A ventilation exhaust system contains charcoal filter banks located in the MER. In addition, ventilation system hot exhaust from Zone 1 and Zone 2A is routed through a HEPA filter before entering the HCF stack. These ventilation systems are described in more detail in Chapter 2. 

Series-Parallel RLC Resonant Filter The Pole Zero Pattern Description of Resonance Time-Domain Description of Resonance Resonance and Energy Storage in Inductors and Capacitors Physical Hazards with Resonant Circuits... 

The one-pass system consists of a feed tank, filter, pump, and membrane system (Fig. 6). The feed tank contains whiskey at approximately 100° proof. It is filtered through a cellulose filter and then pumped into the membrane system where the separation takes place. Dupont B-10 A ram id hoUow fiber membranes are used in series or parallel and are able to withstand the high pressures, 689—1034 kPa (6.8—10 atm), necessary to achieve separation. 

But w hen the third and/or second harmonics are also present in the system, at a certain fault level it is possible that there may occur a parallel resonanee between the capacitor circuit and the inductance of the system (source), resulting in very heavy third or second harmonic resonant currents, which may cause failure of the series reactor as well as the capacitors. In such cases, a 6% reactor will not be relevant and a harmonic analysis will be mandatory to provide more exacting filter circuits. 

These are meant to be used with a capacitor to tune a filter circuit, with resonances in the audio frequency range for reducing and filtering the harmonics or communication frequencies. They provide a near short-circuit for the required harmonics to filter them out of circuit. They may be single-phase or three-phase and connected in series or parallel of the capacitor circuit and may have a fixed or variable reactance, rated continuously with saturated magnetic characteristics. They may incur heavy losses. 

Frequently, eapaeitors are plaeed in parallel to reduee the eombined equivalent series resistanee (ESR) of the filter eapaeitor funetion. This praetiee also allows eaeh eapaeitor to share a portion of the overall ripple eurrent sueh that eaeh eapaeitor ean operate within its ripple eurrent speeifieation. Equal sharing of the ripple eurrent ean only oeeur when the traee impedanee between eaeh of the eapaeitors and the souree of the ripple eurrent is identieal to one another. This means that the traees between the reetifier or the power switeh must be of equal length and width for eaeh eapaeitor. 

This unit is good to pre-thicken feed to centrifugal filters and similar applications. One cyclone may satisfy a requirement, or the units can be arranged in parallel for large capacities or in series for removal of extreme fines. See Figure 4-53 for a counter-current wash system. Solids as small as 10 microns can be separated. 

Pressure filters or filter presses are commonly of the batch type, and are characterized by smaller floor area, high filtration rates, and lower capital cost. Dryer cakes are produced. The chemical industry uses these filters more widely than mineral processing industries, mainly because of its batch operation. The most common types of pressure filters used are the plate and frame presses. These comprise a series of vertical, alternating parallel frames and plates, with the filter cloth being held against the plate and the formation of cake occurring in the hollow frame. 

Each serie of measurements consisted of two parallel samples with counting during and after sampling, one with the screen diffusion battery and the second as the reference sample, so that the fractional free radon daughters could be calculated. The radon daughters are collected on a membrane filter (filter diameter 25 mm, pore diameter 1.2 ym) and the decays of Po-218 and Po-214 are counted by means of alpha spectrometry with a surface barrier detector (area 300 mn ). 

A. The filter system shall include a- series redundant-parallel Chemical Biological Radiological (CBR) filter assembly with a capability of placing a detector between the adsorber banks to warn of "breakthrough". The system shall provide accessibility to filters for repairs, maintenance and leak testing. 

J1. Two tOO-barrel tanks are available to use as surge volume to filter liquid flow rate disturbances in a petroleum refinery. Average throughput is 14,400 barrels per day. Should these tanks be piped up for parallel operation or for series operation Assume proportional-only level controllers. 

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