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Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
Also known as RMS power or average power. = -x D2 ( pi ) D ( pi ) rotate a logical operation on a data element that shifts each bit one position to the left or right. The bit at the end of the location is transferred to the opposite end of the element. rotating excitation system an excitation system derived from rotating AC or DC machines. The output of the system is still DC and connected to the rotor. rotating wave approximation assumption in a semiclassical model for the interaction of light with atoms that all populations, field amplitudes, and polarization amplitudes change negligibly within one optical cycle. rotating-rectifier exciter an AC generator, with rotating armature and stationary field, whose output is rectified by a solid-state device located on the same shaft to supply excitation to a larger electrical machine, also connected to the same shaft. rotational latency the time it takes for the desired sector to rotate under the head position before it can be read or written. rotational loss one of several losses in a rotating electric machine that are primarily due to the rotation of the armature and include the friction and windage losses. Also called mechanical loss. They can be determined by running the machine as a motor at its rated speed at no load, assuming the armature resistance is negligible. rotational position sensing a mechanism used in magnetic disks, whereby the disk interrupts the I/O controller when the desired sector is under the read/write head. Used to recognize the different
Frequency and Voltage Control
Published in Antonio Gómez-Expósito, Antonio J. Conejo, Claudio Cañizares, Electric Energy Systems, 2017
Göran Andersson, Carlos Álvarez Bel, Claudio Cañizares
Different types of exciter systems are used. Three main types can be distinguished as follows: DC excitation system, where the exciter is a dc generator, often on the same axis as the rotor of the synchronous machine.AC excitation system, where the exciter is an ac machine with rectifier.Static excitation system, where the exciting current is fed from a controlled rectifier that gets its power either directly from the generator terminals or from the power plant’s auxiliary power system, normally containing batteries. In the latter case, the synchronous machine can be started against an unenergized net (black start). The batteries are usually charged from the grid.
Frequency and Voltage Control
Published in Antonio Gómez-Expósito, Antonio J. Conejo, Claudio A. Cañizares, Electric Energy Systems, 2018
Claudio A. Cañizares, Carlos Álvarez Bel, Göran Andersson
In static excitation systems, the exciter winding is fed through a transformer and a controlled rectifier. By far, most exciter systems installed today are of that type, and a large number of variants exists. The primary voltage source can be a voltage transformer that is connected to the generator terminals, but even a combination of voltage and current transformers can be found. With the latter arrangement, an exciter current can be obtained even if the voltage at the generator terminals is low (e.g., during a ground fault at or near the power plant). Sometimes, it is possible to supplement these voltage sources by using the auxiliary power of the power plant as a voltage source, this makes it possible to start the generator in an unenergized grid.
Modelling and sizing techniques to mitigate the impacts of wind fluctuations on power networks: a review
Published in International Journal of Ambient Energy, 2022
M. V. Tejeswini, I. Jacob Raglend
The main aim of the excitation system is to control the generator field current. By varying the field current, terminal voltage can be handled. There are four types of AC, DC and static excitation system. DC excitation system consists of a Direct Current generator with a commutator. AC excitation system uses an alternator and either stationary or rotating rectifier to produce the required direct current. Static excitation system is the one in which the power is supplied through transformers and rectifiers. For each excitation system, the models are categorised into a few universally accepted types which can be handled conveniently in Matlab simulation. Type 4 AC alternator-controlled rectifier exciter is given in Figure 16. Type-4 AC alternator-controlled rectifier exciter can be replaced by power system stabiliser to improve the damping of the system.
Modeling the Interaction of Electrodynamic Fields to Circuit Elements
Published in IETE Journal of Education, 2018
For circuit analysis purposes, the electric field , magnetic vector potential , and electric potential Φ of (5) consists of two parts: an excitation component (, , and ) and a reaction component (, , and ). The excitation component is the electrodynamic fields originating from the voltage or current sources (or charges and currents) external to the circuit. The reaction component is the fields originating from the currents and charges in the circuit elements ( i.e. resistors, capacitors, and inductors) resulting from the sources (within the circuit) [19, 25].
Optimal Coordinated Frequency and Voltage Control of CCGT-Thermal Plants with TIDF Controller
Published in IETE Journal of Research, 2021
Satish Kumar Ramoji, Lalit Chandra Saikia
An AVR loop is imperative to maintain the voltage constancy in the generators, and the ALFC loop is vital for maintaining the frequency constancy during the incertitude nature of load [25]. The AVR loop constitutes an amplifier, static or DC excitation mechanism, generator field, and sensor. The excitation mechanism mainly accomplishes the voltage regulation as the excitation mechanism has complete control over the synchronous machine's field current. As a result, the field current is regulated in order to regulate the generator's terminal voltage. The generator's voltage is proportional to its speed and excitation [26]. The excitation mechanism will regulate the generator's terminal voltage if the speed is maintained at a constant level. The exciter is the source of excitation for the generator. The exciter is known as a DC exciter or a static exciter, depending on how DC power is delivered to the generator's field winding. This sensor senses the error voltage and can reliably calculate terminal voltage (ΔV) by comparing it with the reference voltage. An amplifier improves the inadequate voltage in order to control the voltage of the generator's field windings. So the excitation voltage (E) of the generator is being affected by the magnitude of the real power (Pe), which is given as [1]. V is terminal voltage, Xs is synchronous reactance, and (δ) is the phase angle difference between V and E. After a sudden change in load, the frequency, and voltage changes, so the change in real power is given by (3), change in terminal voltage is given by (4), and the change in excitation voltage is given by (5) K1 is the constant flux linkages, K2 is phase angle difference linked to the change in power to alter the direct flux axis. K5 is the change in terminal voltage to change in phase angle, depending on impedance, K6 is the change in terminal voltage to change in excitation voltage. is given by (5), where K3 is the impedance factor, K4 is change in rotor angle due to demagnetizing effect is given by Egf is the generator field's voltage in p.u. and Tfoc is the time constant for the field windings.