A transformer is a passive electrical device that transfers electrical energy from one electrical circuit to one or more circuits. A varying current in any one coil of the transformer produces a varying magnetic flux, which, in turn, induces a varying electromotive force across any other coils wound around the same core. Electrical energy can be transferred between the coils, without a metallic connection between the two circuits. Faraday's law of induction discovered in 1831 described the induced voltage effect in any coil due to changing magnetic flux encircled by the coil. Transformers are used for increasing alternating voltages at low current or decreasing the alternating voltages at high current in electric power applications, for coupling the stages of signal processing circuits. Since the invention of the first constant-potential transformer in 1885, transformers have become essential for the transmission and utilization of alternating current electric power. A wide range of transformer designs is encountered in electric power applications.
Transformers range in size from RF transformers less than a cubic centimeter in volume, to units weighing hundreds of tons used to interconnect the power grid. An ideal transformer is a theoretical linear transformer, lossless and coupled. Perfect coupling implies infinitely high core magnetic permeability and winding inductances and zero net magnetomotive force. A varying current in the transformer's primary winding attempts to create a varying magnetic flux in the transformer core, encircled by the secondary winding; this varying flux at the secondary winding induces a varying electromotive force in the secondary winding due to electromagnetic induction and the secondary current so produced creates a flux equal and opposite to that produced by the primary winding, in accordance with Lenz's law. The windings are wound around a core of infinitely high magnetic permeability so that all of the magnetic flux passes through both the primary and secondary windings. With a voltage source connected to the primary winding and a load connected to the secondary winding, the transformer currents flow in the indicated directions and the core magnetomotive force cancels to zero.
According to Faraday's law, since the same magnetic flux passes through both the primary and secondary windings in an ideal transformer, a voltage is induced in each winding proportional to its number of windings. The transformer winding voltage ratio is directly proportional to the winding turns ratio; the ideal transformer identity shown in eq. 5 is a reasonable approximation for the typical commercial transformer, with voltage ratio and winding turns ratio both being inversely proportional to the corresponding current ratio. The load impedance referred to the primary circuit is equal to the turns ratio squared times the secondary circuit load impedance; the ideal transformer model neglects the following basic linear aspects of real transformers: Core losses, collectively called magnetizing current losses, consisting of Hysteresis losses due to nonlinear magnetic effects in the transformer core, Eddy current losses due to joule heating in the core that are proportional to the square of the transformer's applied voltage.
Unlike the ideal model, the windings in a real transformer have non-zero resistances and inductances associated with: Joule losses due to resistance in the primary and secondary windings Leakage flux that escapes from the core and passes through one winding only resulting in primary and secondary reactive impedance. Similar to an inductor, parasitic capacitance and self-resonance phenomenon due to the electric field distribution. Three kinds of parasitic capacitance are considered and the closed-loop equations are provided Capacitance between adjacent turns in any one layer. However, the capacitance effect can be measured by comparing open-circuit inductance, i.e. the inductance of a primary winding when the secondary circuit is open, to a short-circuit inductance when the secondary winding is shorted. The ideal transformer model assumes that all flux generated by the primary winding links all the turns of every winding, including itself. In practice, some flux traverses paths; such flux is termed leakage flux, results in leakage inductance in series with the mutually coupled transformer windings.
Leakage flux results in energy being alternately stored in and discharged from the magnetic fields with each cycle of the power supply. It is not directly a power loss, but results in inferior voltage regulation, causing the secondary voltage not to be directly proportional to the primary voltage under heavy load. Transformers are therefore designed to have low leakage inductance. In some applications increased leakage is desired, long magnetic paths, air gaps, or magnetic bypass shunts may deliberately be introduced in a transformer design to limit the short-circuit current it will supply. Leaky transformers may be used to supply loads that exhibit negative resistance, such as electric arcs, mercury- and sodium- vapor lamps and neon signs or for safely handling loads that become periodically short-circuited such as electric arc welders. Air gaps are used to keep a transformer from saturating audio-frequency transformers in circuits that have a DC component flowing in the windings. A saturable reactor exploits saturation
The Nissan Xterra is a front-engine, 2-wheel or 4-wheel drive, five-door, five passenger, truck-based compact SUV manufactured and marketed by Nissan Motors from 1999–2015 across two generations. While the two Xterra generations differed both prioritized ruggedness and affordability over luxury and used body-on-frame construction along with underbody skid plates. Both generations used a two-box design with c-pillar-mounted rear door handles, asymmetrical rear window, tailgate bump-out for a first aid kit accessible from inside – and a prominent two-tiered roof enabling stadium seating in the second row; the stepped roof accommodated a lower, front roof rack with a removable gear basket and a more conventional roof rack at the rear, upper roof. Nissan licensed the Xterra name from the XTERRA off-road triathlon race series and manufactured the SUV at Nissan's Smyrna Assembly, as well as in Canton, Mississippi. Variants were manufactured in Brazil and China. Developed at Nissan Design America in La Jolla, the Xterra was the first Nissan vehicle conceived and manufactured in the United States.
According to Jerry Hirshberg, president of Nissan Design International, "the impetus for Xterra designers was to create an affordable, quality piece of equipment". Road & Track described the Xterra as "an honest SUV that doesn't try to be a luxury car alternative, nor tries to hide its truck underpinnings". Jalopnik called it a "knockoff of the Land Rover Discovery"; the Washington Post described it as "rugged without bravado". The Xterra was introduced in North America in the 2000 model year, using Everything you need, nothing you don't as its marketing tagline. During the Xterra's first two years two trim level were offered, marketed as XE and SE; the XE featured a 143 hp KA24DE I4, 5-speed manual transmission, steel wheels as well as several option packages combining the 170 horsepower 3.3 L VG33E V6 engine with either a 5-speed manual or 4-speed automatic transmission, as well as roof rack, side step-rails and carpeted floor mats. The SE featured standard equipment, optional on an XE. All models featured removable, tab-secured rear seat cushions to accommodate a fold-flat rear seat back.
Canadian models from 1999 to 2004 were limited to the VG33E V6 engine with part-time 4WD. With the 1999 Xterra having been developed at Nissan Design America in California, all updates for the 2002 Xterra were executed at Nissan Technical Center-North America in Farmington Hills, Michigan; the facelifted model debuted at the 2001 Chicago Auto Show with revisions with prominently revised front-end styling with rounded headlights revised dash, center console, larger glove compartment, pullout rear cup holders and four interior power points, foot-operated pedal parking brake — and an increase of 10 horsepower for the V6 engine. The 3.3L VG33E V6 was upgraded to 180 hp at 4,800 rpm and 202 lb⋅ft at 2,800 rpm, with the 210 hp supercharged VG33ER option carried over from the 2001 Nissan Frontier, producing 246 lb⋅ft of torque for the automatic, 231 lb⋅ft of torque with 5-speed manual. For 2003, options included a tire pressure monitoring system; the 6-disc, 4-speaker AM/FM/CD audio system was replaced by a 6-speaker 300W Rockford Fosgate AM/FM/CD audio system with an 8-inch subwoofer that took up a small portion of the rear storage area.
The last of the model year 2004 Xterras were manufactured in January 2005. The second generation Xterra debuted at the New York International Auto Show in 2004 using Nissan's F-Alpha platform. Larger in all dimensions than its predecessor, it entered showrooms in early 2005 for the 2005 model year; the standard engine was upgraded to Nissan's 4.0 L VQ40DE variable valve timing V6, producing 261 hp. A rear differential locker was offered for off-roading; the Xterra received a facelift for 2009 with more options and colors, leather seats on SE models, roof mounted lights on off-road models. The last year of the Nissan Xterra in Mexico was 2008. In 2012, production was moved from Tennessee, to Nissan's facility in Canton, Mississippi. Early US models include X, S and PRO-4X, with a choice of 6-speed manual or 5-speed automatic transmissions, a choice of part-time 4-wheel drive or 2-wheel drive. Changes include: Standard Bluetooth Hands-free Phone System, steering wheel audio controls and sunglass holder on all grade levels.
Capabilities include SiriusXM, streaming audio via Bluetooth, Hands-free Text Messaging Assistant and audio voice recognition. New 16-inch aluminum-alloy wheel designs for the S and PRO-4X. New HVAC upgraded audio system added to X grade. Heated front seats available on PRO-4X. Silver underguard; the Xterra was discontinued in the U. S. after the 2015 model year. Poor fuel economy, declining sales, mandated upgrades to safety and emissions were cited as reasons. 2000 Motor Trend's Sport Utility of the Year 2000 North American Truck of the Year 2000 New England Motor Press Association's Winter Vehicle Award of New England for Best in Class – Mini Sport Utility 2001 Named Top Car by AAA New Car and Truck Buying Guide 2005 Named on the Automobile Magazine's 50 Great New Cars list 2006 Nomi
Rana Ijaz Ahmad Noon is a Pakistani politician, a Member of the Provincial Assembly of the Punjab, from 2002 to May 2018. He was born on 8 April 1968 in Multan, he received his early education from Aitchison College and obtained a degree of Bachelor of Arts in 1989 from Government College University. He was elected to the Provincial Assembly of the Punjab as a candidate of Pakistan Muslim League from Constituency PP-204 in 2002 Pakistani general election, he defeated Rafique Ahmad, a candidate of Pakistan Muslim League. He was re-elected to the Provincial Assembly of the Punjab as a candidate of PML-Q from Constituency PP-204 in 2008 Pakistani general election, he defeated Khurram Fareed Khan, a candidate of Pakistan Peoples Party. He was re-elected to the Provincial Assembly of the Punjab as a candidate of PML-N from Constituency PP-204 in 2013 Pakistani general election. In December 2013, he was appointed as Parliamentary Secretary for agriculture, he was re-elected to Provincial Assembly of the Punjab as a candidate of PML-N from Constituency PP-221 in 2018 Pakistani general election