Capacitors resonant

Bulk and surface imprinting strategies are straightforward tools to generate artificial antibodies. Combined with transducers such as QCM (quartz crystal microbalance), SAW (surface acoustic wave resonator), IDC (interdigital capacitor) or SPR (surface plasmon resonator) they yield powerful chemical sensors for a very broad range of analytes. 

When harmonic filter circuits are connected to a power system with saturated reactors (Figure 27.2(e)) resonance may occur between the reactor and the filter capacitors to give rise to overvoltages. 

Resonance may also occur between the line inductance, series reactors and shunt capacitors. 

A filter circuit is a combination of capacitor and series reactance, tuned to a particular harmonic frequency (series resonance), to offer it the least impedance at that frequency and hence, filter it out. Say. for the fifth harmonic, =... 

Yet another reason for harmonic disorder in a power circuit is the occurrence of series or parallel resonance or a combination of both. Such a situation may occur at certiiin frequencies generated by the harmonic generating sources in the system. The capacitors installed in the system magnify the same. 

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. 

As one can see, there is the familiar choke input filter (T-C) on the output, which is characteristic of the buck and all forward-mode converters. The configuration shown in Figure 4—10 is called a parallel resonant topology because the load impedance (the T-C filter acting as a damping impedance) is placed in parallel to the resonant capacitor. The input to the T-C filter stage... 

Figure 4-16 "Pushing" the resonant capacitor through a transformer in ZCS QR supplies (a) primary-side resonance (b) secondary-side resonance.

One caution Whenever the resonant capacitor is placed on a lower voltage output, the ripple current entering the capacitor increases. So, carefully check the ratings against the application. 

It is desired that the resonanee frequency of the tank circuit be 1 MHz. In ZVS QR converters, the tank circuit is not responsible for storing and passing on energy as it is in ZCS QR converters. The tank circuit can be seen more as an off-time transition shaper similar to a snubber when used in PWM converters. Here a wide range of values for both the inductor and the capacitor will work as long as their combined resonant frequency is 1 MHz or... 

Just as an estimate, let us calculate the approximate value required for the resonant capacitor. 

This value is higher than that exhibited by the output capacitance of the MOSFETk so I will add an external resonant capacitor outside the MOSFET. 

A capacitor bank will represent reducing impedance to currents of increasing frequency. Such reducing impedance, if matched with a similarly increasing inductance impedance of a transformer or a supply system, can cause a resonant condition. In plants where equipment produces harmonic current, a full survey of the installation is recommended prior to installation of the capacitors. 

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