Abstract: A three phase bidirectional AC to AC buck converter circuit using power MOSFET is designed, rigged up and analyzed with three phase starconnected RL load for electrical parameters such as output voltage, input current, input power factor, harmonic profile and efficiency using FPGA real time controller. The various PWM techniques such as ramp-DC symmetrical PWM (RDSPWM), ramp-triangular asymmetrical PWM (RTAPWM), sinusoidal asymmetrical PWM type-1 [SAPWM1] and sinusoidal asymmetrical PWM type-2 [SAPWM2] techniques are generated using FPGA real time controller in order to analyze the harmonic profile, input power factor and efficiency of the converter It is required to consider both harmonic profile and input power factor in order to increase the efficiency of power electronic converter. It is observed from experimental results that the RDSPWM technique gives lesser total harmonic distortion [THD] of output voltage and input current than other techniques. It is also observed that the SAPWM1 switching strategy gives high input power factor, more output voltage, high efficiency and moderate improvement of harmonic profile for the entire range of modulation index MI compared to other PWM techniques. Hence SAPWM1 technique is preferred for AC to AC converter than other techniques that renders easy filtration at lower cost. Index Terms: AC Chopper, RDSPWM, SAPWM1, SAPWM2, RTAPWM techniques, input power factor, THD, efficiency, FPGA real time controller
Internal Earth Faults in a StarConnected Winding with Neutral Point Earthed through an Impedance In this case the fault current is dependent on the value of earthing impedance and is also proportional to the distance of the fault point from neutral point as the voltage at the point depends upon, the number of winding turns come under across neutral and fault point. If the distance between fault point and neutral point is more, the number of turns come under this distance is also more, hence voltage across the ne utral point and fault point is high which causes higher fault current. So, in few words it can be said that, the value of fault current depends on the value of earthing impedance as well as the distance between the faulty point and neutral point. The fault current also depends up on leakage reactance of the portion of the winding across the fault point and neutral. But compared to the earthing impedance, it is very low and it is obviously ignored as it comes in series with comparatively much higher earthing impedance.
To model a six-phase induction machine, some researchers suggested equal number of phases in both stator and rotor while others maintain unequal number of phases. But using a three-phase rotor for the modelling of sixphase induction machine according to , gives a clear concept of per phase equivalent circuit or arbitrary rotating reference frame equivalent circuit. Improved reliability is a priority in the drive system of most induction motors like the compressors in methane tankers, electric propulsion of ship and railway traction, [16,17]. To achieve the desired reliability, the application of a dual three phase induction machine which is composed of two sets of starconnected stator winding spatially shifted by 300 electrical with isolated neutral point was proposed in . In  a comparative analysis of the performance of six-phase and the conventional three phase synchronous generator for wind farm application was carried out and the results presented. This result shows that the six-phase motor performance is better than the conventional three- phase. In this paper, the modelling of six phase induction machine is presented with improved load torque and efficiency. Generally, power generation, transmission and distribution which is conventionally three phase can receive a boost when multiphase generators (synchronous and induction) are adopted .
Based on the type of faults, sags are classified into four basic types namely A, B, C and D. A single phase fault causes sag of type B, while symmetrical fault causes sag of type A. Phase to phase fault causes sag of type C at starconnected load and type D at delta connected load terminals. The fig. 1 represents the four sag types in phasor. In the figure, the presag voltages are given by and ′ where j= a, b and c respectively.
The circuit model of three phase rectifier with boost converter and three-phase inverter system is shown in Figure 3. The output is connected to the three phase stator of starconnected induction motor. The power devices are assumed to be ideal, when they are conducting, the voltage across them is zero, they present an open circuit in their blocking mode. The phase voltages are derived from the line voltages in the following manner by assuming a balanced three-phase system .
The star-connected load consists of a resistance of 15 Ώ, in series with a coil having resistance of 5 Ώ, and inductance of 0.2 H, per phase. It is connected in parallel with the delta-connected load having capacitance of 90 μ F per phase (Fig. 18.10a). Both the loads being balanced, and fed from a three-phase, 400 V, 50 Hz, balanced supply, with the phase sequence as R-Y-B. Find the line current, power factor, total power & reactive VA, and also total volt-amperes (VA).
Abstract—Designing an Internet of Things (IoT) enabled environment re- quires integration of various things/devices. Integrating these devices require a generalized approach as these devices can have different communication proto- cols. In this paper, we have proposed generalized nodes for connecting various devices. These nodes are capable of creating a scalable local wireless network that connects to the cloud through a network gateway. The nodes also support over the air programming to re-configure the network from the cloud. As num- ber of devices connected to the cloud increases, the network traffic also increas- es. In order to reduce the network traffic we have used different data transfer schemes for the network. We have also proposed an event-based data transfer scheme for situations where there is low probability of change in sensor value. The experimental results shows that the event-based scheme reduces the data traffic by up to 48% under practical conditions without any loss of information compared to priority based data transfer. We have also shown that the proposed scheme is more reliable for data transfer in a large network with a success rate of 99.5% measured over 200 minutes for 1201 data packets.
A well researched, laid out and engrossing guide to the vast Star Trek universe. You stop to look up one thing and next thing you know it is 30 minutes later and you've read through an entire letter's worth of entries.My ONLY complaint about this book (and what keeps it from it's fifth star) is that the new entires weren't integrated, but simply stuck in the back as add on. So let's say you want to read the complete entry on Capt Sisko. First you have to read the original entry and then flip to the back of the book to read the additional information. And since you are never sure what got an additional entry, you have to constantly flip to the back to make sure you aren't missing something.Luckily the Pros far out weigh the cons, and this is still a must have for any die hard fan!
In the above theorems we find the new approach of planarity by finding the crossing between the edge and non-edge. This can be extended for any composition of graphs. Note that that the edge non-edge crossing number is meant for all graphs except star graphs and complete graphs. Practically, this situation or set up may arise in future for launching network cables, electrical circuits. If we come across a situation in which case we need not care about the crossings of the cables (edges) which are connecting between the networks, but we need to minimize or avoid the crossings of the separators (non-edge) which will be of great use.
Here separates iron core are designated with one primary and three secondary coils, six terminal of primary side are connected in an adoptable manner resulting in star and or delta connection and the thirty terminals of secondary’s are connected in a different fashion in a star/ Tridecagon output. The new connection scheme of secondary winding to obtain an input star and output star is illustrated in figure 2 and the corresponding phasor diagram is shown in figure 4 similarly for input delta and output star connection is also shown in the figure 3. The construction of the output (star) phase with requisite phase angles of 360/13=27.69° between each phase is obtained using appropriate turn ratio and the governing phasor equation is given in (3). Selecting the turn ratio is the key in creating the phase displacement in the output phases.
When computer networks were first designed, future expansion and/or upgrading needs were not anticipated. Original networks were small, often as few as two or three computers and a printer connected together in the same office. Existing equipment was cabled together in a somewhat haphazard manner and networks that went beyond single-site locations were neither envisioned nor planned for. There was no need for cabling and networking standards.
In this case, the structure of graphs can be described as follows: take a collection of stars and create a clique on their central vertices and then add a number (possibly zero) of isolated vertices. In other words, applying subgraph complementation once (to the clique X), we obtain a graph which is a disjoint union of stars and isolated vertices. Clearly, a graph every connected component of which is a star or an isolated vertex is P 6 -free bipartite and hence
The working principle of BLDC motor are as same as like for brushed DC motor but there is little difference in commutation process. In case of Brushed DC motor feedback is implemented by use of mechanical parts like brushes and commutator while In case of Brushless DC motor feedback is achieved by hall sensors. A three phase Brushless DC motor mainly consists of star (Y) connected type stator, permanent magnet type rotor as well as for detection of position of rotor it consists of hall sensors. On the basis of rotor position sensed, there are two types of outputs: a 60˚ and 120˚ phase shift. after 60˚ rotation of rotor one of the three hall sensors changes its state which used to updates the phase current switching by every 60˚.
As before, in order to study empirically the connected-ness of practice through its effects we can employ the theoretical and methodological toolkit of the sociology of translation. The theory provides, in fact, an interesting explanation for the ways in which effects are translated in time and space. It does so by noting that mediators, which include boundary objects, names, protocols, plans, forms of categorisation and rules do not only support the association between practices. They also move it around acting as generalisers and localisers (Latour, 2005, p. 181). As generalisers, mediators summarise and black box the inherent multiplicity of practices, making them available as an object of work in another context; human experts “summarise” years of learning by doing, and artefacts such as the portable ECG black box the work and knowledgeability of all those who designed and built it. Through generalising mediators, large associations of practicing can become the objects of work of other, equally local and equally socio-material practices. It is through the mediatory work of these
Once a student enrolls in Lone Star College, that person is making a decision to join one of the finest community colleges in the country. Offering a wide range of academic and workforce courses for recent high school graduates and community residents of all ages, LSCS is one of the largest and fastest growing community colleges in Texas. More than 69,000 students register for credit courses each semester with an additional 22,000 in continuing education courses. The college system serves an area over 1,400 square miles, encompassing the school districts of Aldine, Conroe, Cypress-Fairbanks, Humble, Klein, Magnolia, New Caney, Splendora, Spring, Tomball, Willis, and the surrounding communities.
1999). Moreover, the detection of this soft thermal component from GRO J1744–28 suﬀers considerably from the high Galactic extinction in the direction of the source. The mechanism respon- sible for the quiescent emission of GRO J1744–28 is therefore a subject of debate (Wijnands & Wang 2002; Daigne et al. 2002). The spectral index for the powerlaw fit is very similar to that of the hard emission tails that are often detected for neutron star LMXBs above ∼2–3 keV (e.g., Rutledge et al. 1999). Its origin is not well understood, but possible explanations include accre- tion onto the surface or the magnetic field of the neutron star, or a shock generated between the pulsar wind and the material flowing out of the donor star (e.g., Campana et al. 1998).
The coordinate system of the star sensor image plane is s-xyz. The origin of the coordinate system is the center of the star sensor. The z-axis is the optical axis of the sensor system. The attitude of the star sensor in the equatorial inertial coordinate system O-XYZ is described by the right ascension angle, α, the declination angle, β, and the rotation angle of the star sensor image plane, κ, as shown in Figure 1.
During our attempts to fit KIC 2856960 two other peculiar prob- lems surfaced that we never resolved. The elusive second compo- nent of the binary is one of these. In all the models that provide a reasonable fit to the dips, star 2 is 2.5 to 4 times smaller than star 1. We mentioned this as the chief drawback of the quadruple models in the previous section, because there star 2’s small radius is out of kilter with its mass. Such unequal ratios are also not favoured by the binary light curve, although in section 3.2 we argued that star spots made the true ratio uncertain. However, there can be no doubt that the two eclipses in the binary light curve have a similar depth, implying a similar surface brightness for each component of the binary. It is then very hard to understand how these two stars, which are most likely unevolved, low mass main-sequence stars, can differ so much in radius.