Application and control of motors

Milking Machines. The action required to milk a cow is obtained mechanically by a vacuum pump. The size of the pump varies with the size of milking plant: the smallest unit, for milking a herd of 20 cows, has a 3/4 hp motor; the largest vacuum pump for herds up to about 300 cows has a 5 hp motor. For herds of 150 cows it is usual to have more than one vacuum pump.

Motors used are totally enclosed. The vacuum pump with a driving motor is usually housed in a separate room from the milking shed or parlour and from the area used for cooling and storage.

Starting is invariably by hand switching which may be re­mote from the motor position. A control switch at the milking point is a definite advantage as the operator can quickly stop the plant in an emergency. All motors must have a suitable starter to give overload and no-volt protection. In smaller sizes, usually up to 2 hp direct on-line starting is permitted.

Milk Pumps. The vacuum in the system is used to convey the milk from the cow to an adjacent receptacle where the milk can be released without breaking the vacuum. In the more complex plants the milk is pumped from the release point to the dairy. A small motor (up to about 2 hp) is used to drive the pump which is directly mounted on the motor shaft. Milk pumps are made from stainless steel and dismantle easily for cleaning. Totally-enclosed motors are used as it is usual for these units to be in damp, or even wet, situations. Starting can be direct on-line but it is important that a suitable starter is used to give protection.

ВАРИАНТ 2

1. Перепишите следующие предложения, подчеркните в каждом из них глагол-сказуемое и определите его видовременную форму и залог. Переведите предложения на русский язык. В разделе (б) обратите внимание на перевод пассивных конструкций.

а) 1. Today scientists are still looking for the substance as a source of energy.

2. I have known this fact since our meeting.

б) 1. This lecturer is listened to with great interest.

2. The intensity of this process is influenced by many factors.

II. Перепишите следующие предложения; подчеркните Participle I и Participle II и установите функции каждого из них, т.е. укажите, является ли оно определением, обстоя­тельством или частью глагола-сказуемого. Переведите пре­дложения на русский язык.

1. Molecular crystals are solids constructed of molecules held together by relatively weak forces.

2. The new materials recommended for soil construction were described in the article written by our professor.

3. Having been shown the way I found the office easily.

III. Перепишите следующие предложения; подчеркни­те в каждом из них модальный глагол или его эквивалент. Переведите предложения на русский язык.

1. Energy can exist in many forms and each form can be transformed into the other.

2. The computers should become an integral part of the orga­nization of industrial processes of all types.

3. Students are not allowed to smoke in the classrooms.

4. One should agree that the experiment was of great importance for our research.

IV. Перепишите и письменно переведите текст.

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