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Introduction to Semiconductor Physics
Published in Lev I. Berger, Semiconductor Materials, 2020
where β is a constant (0 < β ≤ 1) and V is the voltage of the current source, positive for the forward bias and negative for the reverse bias. I, is called the saturation current, which depends on diffusion characteristics of electrons and holes in the crystal. At V > 0 and relatively low temperatures, the first term in the right-hand side of Equation 2.41 grows very fast with V increase, so the second term is negligibly small in comparison with it and the current has an exponential dependence on voltage. With V < 0, the exponential term in the right-hand side becomes negligibly small with the voltage increase, and I = —I2 = constant for a certain range of voltage. The described property of p-n junction is utilized in the semiconductor rectifiers. The same property can be used to make a variable capacitor which capacitance is controlled by applied voltage. Formation in a crystal of two reverse-oriented p-n junctions permits to make a solid-state amplifier of electric signals called a transistor. Intensive recombination of electrons and holes in the depletion layer at the forward bias, resulting in release of energy in the form of electromagnetic radiation, is used in the light-emitting diodes and semiconductor lasers. Specially designed diodes similar to the light-emitting diodes are used for transformation of solar energy in the energy of electric current.
Antennas for Interrogators
Published in Albert Lozano-Nieto, RFID Design Fundamentals and Applications, 2017
In practice, the point at which the central conductor of the coaxial cable is connected (point A) must be determined by experimentation. The designer of the system connects an antenna analyzer at the far end of the coaxial cable and moves point A until the antenna analyzer reads a VSWR value equal to 1. This indicates that the impedance of the antenna between point A and the connection of the central conductor is equal to 50 Ω. The value of the capacitor used to tune the antenna to the resonance frequency was determined using an approximation for the value of the antenna inductance. Therefore, a variable capacitor is initially used in order to tune the antenna to its resonant frequency. Once the correct value of capacitance has been determined, it is then possible to substitute the bulkier variable capacitor with a fixed capacitor.
Fundamentals of Electric Capacitors
Published in Aiping Yu, Victor Chabot, Jiujun Zhang, Electrochemical Supercapacitors for Energy Storage and Delivery, 2017
Aiping Yu, Victor Chabot, Jiujun Zhang
A variable capacitor is constructed to allow a user to adjust its capacitance mechanically. For example, in a radio application, using a variable capacitor coupled with an inductor allows the capacitance to be manipulated to resonate a desired radio station frequency. These tuner capacitors have low capacitance values in a range of 10 to 500 pF and are used primarily for frequency filtering. The dielectric materials used in these devices include air, plastic foil, and inert sulfur hexafluoride gas. A typical variable device is a trimmer capacitor, which is a miniaturized version of a variable capacitor. In variable capacitors, several dielectric materials including air, ceramic, mica, and polymers are used.
Design and Performance Analysis of Single Phase Line Start Synchronous Reluctance Motor Derived from Single Phase Induction Motor
Published in Smart Science, 2023
Mandar Chaudhari, Anandita Chowdhury
To make a single-phase SynRM line start, the design of single-phase SynRM revisited through an analytical study by the application of revolving field theory in [15]. Introduction of rotor dependence variable in design and analysis through symmetrical component in the synchronous and asynchronous operation is carried out in [16, 17]. It was also demonstrated in this study that good starting and synchronization require two different capacitors. The introduction of barriers and cage bars has been analyzed [18] to improve the performance of self-start single-phase SynRM. The operation of a single-phase cage rotor reluctance motor with a variable capacitor is presented in [19]. The speed error signal was utilized to control the capacitor value. An additional control circuit in the feedback loop and the variable capacitor increases the system cost. Recently, a line-start single-phase SynRM was developed, and its performance was compared with SPIM [20]. The increase in efficiency noted, in this case, was 6%. Structural optimization of high efficient line-start SynRM (LS-SynRM) for heavy metal industry application is reported in [21]. A new bearingless SynRM with PM is introduced in the barriers for high torque density [22]. However, in all the above-reported studies, the new rotor was manufactured.
Assessing ignitions of explosive gas mixtures by low-energetic electrical discharges using OH-LIF and 1D-simulations
Published in Combustion Science and Technology, 2023
Johann-Robert Kummer, Stefan Essmann, Detlev Markus, Holger Grosshans, Ulrich Maas
The beam passed between the electrodes (2.4 mm diameter tungsten rods with rounded tips) which were utilized to incorporate electrostatic energy in the gaseous phase from a capacitor used as the electrical source in order to obtain energies close to the respective MIE, using the most incentive mixture as shown in Table 1. The discharge energy was estimated via the relation , where is the discharge energy, is the capacitance of the set-up, and is the voltage at breakdown. The capacitance was adjusted by a variable capacitor in parallel to the set-up. Further details concerning the test vessel and the electrical circuit can be found in the paper by Korytchenko et al. (2018). For the energy levels in this work the aforementioned calculation of the energy is sufficient for obtaining the induced energy (Hattwig and Steen 2004; Moorhouse, Williams, Maddison 1974). Moreover, the calculation of the energy via the time-integration of the voltage and current waveforms is very challenging and has certain downsides (Korytchenko et al. 2020). The reproducibility of the spark energy can be estimated by analyzing data presented in previous work (Markus et al. 2017). Here, we measured the radius of the pressure wave that is induced by the discharge and which is a function of energy. We found it to be within 2% for several experiments at nominally constant energy.
A Fast Model Predictive Control Method for a Single DC Source Driven Dual Inverter Fed Open-end Winding Induction Motor Drive
Published in Electric Power Components and Systems, 2022
Naga Surya Prakash Musunuru, Srirama Srinivas
Recently, the dual-inverter driven from a dc power source and a capacitor bank together feeding the OEWIM is reported in [24–31]. This topology does not suffer from the zero-sequence current issue, thus significantly reduces the overall size of the drive system. Improved voltage quality [25], constant power factor operation [27], reactive power support with a wide speed range of operation [28, 29], improved phase voltage profiles [30], etc., are also reported using this circuit. The work reported in [24] limits the selection of voltage vectors to reduce the computational burden. With the above methods, quality of voltage waveform may get compromised, especially with the variable capacitor voltage demanded in [29]. A cascaded MPC method is reported in [31] that is devoid of weighting factors but is computationally intensive due to the sorting of the objective function values.