外文翻譯---電動(dòng)機(jī)的結(jié)構(gòu)特點(diǎn)-其他專業(yè)-在線瀏覽
2025-03-24 09:40本頁面
【正文】 s. On the other hand the salientpole construction is used exclusively for synchronous motors operating at speeds of 1800 or less. When operated as a generator the synchronous machine receives mechanical energy from a prime mover such as a steam turbine and is driven at some fixed speed. Also, the rotor winding is energized from a DC source, thereby furnishing a field distribution along the air gap. When the rotor is at standstill and DC flows through the rotor winding, no voltage is induced in the stator winding because the flux is not cutting the stator coils. However, when the rotor is being driven at full speed,voltage is induced in the stator winding and upon application of a suitable load electrical energy may be delivered to it. For the synchronous machine the field winding is located on the rotor。ba39。 represents phase b coils, and coil cc39。英文翻譯 第 1 頁 共 8 頁 Construction Features of Electrical Machines The energyconversion process usually involves the presence of two important features in a given electromechanical device. These are the field winding, which produces the flux density, and the armature winding, in which the “working emf is induced. In this section the salient construction features of the principal types of electric machines are described to show the location of these windings, as well as to demonstrate the general position of such machines. Induction Motor This is one of the most rugged and most widely used machines in industry. Its stator is posed of laminations of highgrade sheet steel. The inner surface is slotted to acmodate a threephase winding. In (a) the threephase winding is represented by three coils, the axes of which are 120 electrical degrees apart. Coil aa39。 represents all the coils assigned to phase a for one pair of poles. Similarly coil bb39。 represents phase c coils. When one end of each phase is tied together, as depicted in (b), the threephase stator winding is said to be Yconnected. Such a winding is called a threephase winding because the voltage induced in each of the three phases by a revolving flux density field are out of phase by 120 electrical degrees—a distinguishing characteristic of a balanced threephase system. The rotor also consists of laminations of slotted ferromagic material, but the rotor winding may be either the squirrelcage type or the woundrotor type. The latter is of a form similar to that of the stator winding. The winding terminals are brought out to three slip rings. This allows an external threephase resistor to be connected to the rotor winding for the purpose of providing speed control. As a matter of fact, it is the need
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