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1、外文翻译TransformerA Transformer is a device that change ac electric energy at one voltage level into ac electric energy at another voltage level through the action of a magnetic filed .It consists of two or more coils of wire wrapped a common ferromagnetic core. These coils are (usually) not directly c
2、onnected. The only connection between the coils is the common magnetic flux present within the core.One of the transformer windings is connected to a source of ac electric power, and the second (and perhaps third) transformer winding supplies electric power to loads. The transformer winding connecte
3、d to the power source is called the primary winding or input winding, and the winding connected to the loads is called the secondary winding or output winding. If there is a third winding on the transformer, it is called the tertiary winding. Power transformers are constructed on one of two types of
4、 cores. One type of construction consists of a simple rectangular laminated piece of steel with the transformer windings wrapped around two sides of the rectangle. This type of construction is known as core form. The other type consists of a three-legged laminated core with the windings wrapped arou
5、nd the center leg. This type of construction is known as shell form. In either case, the core is constructed of thin laminations electrically isolated from each other in order to reduce eddy currents to a minimum.Power transformers are given a variety of different names, depending on their use in po
6、wer systems. A transformer connected to the output of a generator and used to step its voltage up to transmission levels is sometimes called a unit transformer. The transformer at the other end of the transmission line, which steps the voltage down from transmission levels to distribution levels, is
7、 called a substation transformer. Finally, the transformer that takes the distribution voltage and steps it down to the final voltage at which the power is actually used is called a distribution transformer. All these devices are essentially the same the only difference among them is their intended
8、use.In addition to the various power transformers, two special-purpose transformers are used with electric machinery and power systems. The first of these special transformers is a device specially designed to sample a high voltage and produce a low secondary voltage directly proportional to it, Suc
9、h a transformer is called a potential transformer. A power transformer also produces a secondary voltage directly proportional to its primary voltage the difference between a potential transformer and a power transformer is that the potential transformer is designed to handle only a very small curre
10、nt. The second type of special transformer is a device designed to provide a secondary current much small than but directly proportional to its primary current. This device is called a current transformerThe ideal transformer without loss of energy, so have a 100% efficiency. In reality, the efficie
11、ncy of power transformer reaches 98%, But small transformer loss will be more serious, and they may be less than 85% of efficiency. The energy loss from transformer in these phenomena: (in a coil of narrative, conductive are called coreThe current through the winding resistance, thermal conductive (
12、current generated when the heat to higher, the human body to feel energy losses caused to). And other kinds of loss, this loss not from the core transformer.Eddy: the magnetic loss to generate electricity, iron loop back into heat energy and loss caused to the outside world. The core of dont cut int
13、o thin can reduce the loss.Magnetism loss: all are not both senders coils magnetic field lines are receiving causes energy drain.Hysteresis: core lagged effect of magnetic field changes that every cause loss of energy. This depends on the size of the loss of the core materials.Alternating magnetic f
14、ield strength loss: that wire, iron and near the electromagnetic force between the metal forming and changing the vibration and energy drain.Magnetostrictive: the magnetic field that appear alternately core.If the core material susceptible to expansion effect of friction between the molecules, will
15、lead to loss of energy.Cooling equipment: large transformer with cooling fan with general of water pump, or the radiator. These devices have been using energy generally count the energy loss of transformer.The overhead three phase power transmission line is the main energy corridor in a power system
16、. One might assume that the circuit model would be trivial (ideal conductors), but three different phenomena produce effects that can not reasonably be ignored. In order of importance, they are the series voltages induced by the magnetic fields surrounding the conductors, the shunt displacement currents resulting from the electric fields between conductors，and the ohmic resistance of the conductor material. A forth，and minor, effect is the leakage conduction c
