时间：2011-03-11 23:18来源：蓝天飞行翻译 作者：航空 点击：次
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synchronous motor (electric motor). An alternating current motor similar to an induction motor, except the rotor is either a permanent magnet or an electromagnet excited by an external source of direct current. The rotor of a synchronous motor turns at a speed directly related to the frequency of the alternating current used to excite its stator. synchronous speed (induction motor). The speed of an induction motor at which the rotor follows the rotating field in the stator. The synchronous speed, in revolutions per minute, is found by dividing the frequency of the AC, in hertz, by the number of poles in the stator. Then multiplying this answer by 120. A four-pole induction motor, operating on 60-hertz AC, has a synchronous speed of 1,800 RPM. synchrophasing (propeller operation). A method of synchronizing the propellers of a multiengine aircraft. The engines all turn at the same RPM, and the propellers rotate in such a way that a master blade on each propeller keeps the same relative position in its rotation as the master blade on each of the other propellers. synchroscope (aircraft instrument). A powerplant instrument used on multiengine aircraft to detect and display the difference in rotational speed of the various engines. One popular type of synchroscope has a small propeller on the face of the instrument. The propeller rotates at a speed and in a direction determined by the difference in RPM of the master engine and the other engine. When the propeller on the instrument face is not rotating, the two engines are turning at exactly the same speed. synchro system (remote indicating system). A type of remote indicating system that uses synchro motors in the transmitter and the indicator. These synchro motors have a three-phase stator and a single-phase rotor. The stators and rotors of the transmitter and indicator are connected in parallel, and alternating current is used to excite the rotors. The AC exciting the rotor induces a voltage in the three phases of the transmitter stator, and since the two stators are connected in parallel, the magnetic fields in the indicator are the same as those in the transmitter. The magnetic fields in the indicator stator pull its rotor around so it assumes the same position as the rotor in the transmitter. An Autosyn system is a form of synchro system. See Autosyn system. synoptic chart (meteorology). A chart, such as a weather map, which shows the distribution of meteorological conditions over an area at a given time. synthetic oil. A type of engine lubricating oil made by chemical synthesis (changing) of a mineral-, animal-, or vegetable-oil base. Synthetic oils have appropriate additives that give them such characteristics as low volatility, low pour point, high viscosity index, good lubricating qualities, low coke and lacquer formation, and low foaming. Synthetic oils are superior to natural mineral oils because they resist oxidation better, and they are able to be used over a wider range of operating temperatures. Synthetic oils are used in almost all gas turbine engines and are used to some extent in reciprocating engines. |
