F. The commutator. The ends of all armature coils are joined to the commutator. A simple, cylindrical commutator it is. It consists of a number of small wedge-shaped segments of copper, which • when assembled together form a cylinder. The copper bars are separated from each other by sheet mica & are insulated from their supporting ring§ by means of mica cones & gaskets.
G7 Brush gear. To collect the' current of a rotating commutator or to lead the current to it a brush-gear is used which consists of: a) brushes, b) brush-holders, c) brush studs or brush-holder arms, d/ brush-rocker, e/ the current-collecting busbars. The brushes employed in modern machines are solely composition’of carbon & graphite or carbon & copper, the latter used for low-voltage commutator DC machines. The brush is inserted into the brush-holder where a spring presses it against the commutator. The brush-holder is mounted on
r \
a stud w;hich maintains the brush in a definite position in relation to the commutator. The current from the brush is led to the stud by means of a special flexible lead. Each brush stud usually carries two or more brushes working in. parallel. All brushes of the same polarity are interconnected by busbars to the machine terminals.
Ключи.
6 - cfgjlmpqrs
7 - dfghjprsuwxa’c’d’
9 - 1, 5
11- 1 bdhiklnqrwx, 2 acgjmsuyz
12- acdf
16 - 1. Результаты были очень благоприятны, особенно результаты Джоунса. 2.Эта реакция аналогична той /реакции/, которую мы наблюдали. ^.Двигатели смешанного возбуждения развивают более высокий пусковой вращающий момент по сравнению с пусковым моментом двигателей параллельного возбуждения. 4.На скорость и молекулярные веса влияет понижение температуры, причем скорость уменьшается, а молекулярные веса увеличиваются. 5.Мы нашли новые пути синтеза,т.к. старые /пути синтеза/ были неудовлетворительными.
18-1. Чем больше размеры и выходная мощность машины, тем большая необходимость выполнения условий симметрии якорной обмотки. 2. На земле столько воды, сколько было всегда: ни больше, ни меньше. 3. В наш век загрязнения /среды/ одним из наиболее обнадеживающих исследований является работа, которая выполняется по очистке сточных вод. 4. Чем больше нагрузка, тем меньше скорость.
41 - А5; В2,3; С 1,4.
Section 2
Тема: “Асинхронные двигатели” Грамматический материал: Предлоги.
Basic Topical Text Induction Squirrel-Cage Motors
1. A great majority of the motors usgd aboard ships are designed to operate on ac. There are some advantages in the use of ac motors besides the wide availability 2. There are two most common types - the induction & synchronous motors. In induction motors the rotor currents are supplied by electromagnetic induction. The stator windings contain one or more out-of-time-phase currents, which produce corresponding mmf. These mmfs currents establish a rotating magnetic field across
the air gap. This magnetic field rotates continuously at constant speed regardless of the load on the motor. The stator winding corresponds to the armature winding of a dc motor or to the primary winding of a transformer. The rotor is not connected electrically to the power supply. The induction motor derives its name from the fact that mutual induction takes place between the stator & the rotor under operating conditions. The magnetic revolving field produced by the stator cuts across the rotor conductors inducing the voltage in the conductors. This induced emf voltage causes rotor current to flow. Hence, motor torque is developed by the interaction of the rotor current & the magnetic field.
3. Majority of motors for a marine installation are of the squirrel-cage type, low in first cost, efficient in running, low in maintenance cost, simple & robust, & reliable.
