- •Memorize the words and word combinations and their equivalents.
- •Find the words and combinations of words in the text and translate the sentences containing them.
- •Read and translate the text.
- •Translate the word combinations from the text:
- •Point out the sentences in the text in which the word “to make” should be translated as “примушувати”.
- •Answer the questions.
- •Find the sentences in the text telling you about two problems facing the simple two pole dc motor. Text b Compensation for stator field distortion
- •Make sure that you know these words and word combinations.
- •Read and translate the text.
- •Answer the questions.
- •Text c Dynamo Design Variations
- •Read and memorise the words and word combinations.
- •Permanent magnet motor – двигун з постійним магнитом
- •Read and translate the text.
- •Answer the questions.
- •Listen to the words and word combinations from the text. Pay attention to their meaning.
- •Memorize the words and word combinations and their equivalents.
- •Read and translate the text.
- •Match the words and word combinations (a-e) to the sentences (1-5)
- •Answer the questions to the text
- •Say if the statement to the text is true or false
- •Translate the sentences paying attention to Indefinite Tenses in Active and Passive. Correct the mistakes in the sentences.
- •Text b Basic construction
- •Listen to the words and word combinations from the text. Pay attention to their meaning.
- •Memorize the words and word combinations and their equivalents
- •Read and translate the text
- •Match the words and word combinations (a-e) to the sentences (1-5)
- •Answer the questions to the text
- •Say if the statements to the text are true or false
- •Translate the sentences paying attention to Indefinite Tenses in Active and Passive. Correct the mistakes in the sentences.
- •Text c Principles of operation
- •Listen to the words and word combinations from the text. Pay attention to their meaning.
- •Find the words and combinations of words in the text and translate the sentences containing them.
- •Memorize the words and word combinations and their equivalents.
- •Read and translate the text
- •Match the words and word combinations (a-f) to the sentences (1-6)
- •Answer the questions to the text
- •Define the functions of Participle I and Participle II in the following sentences
- •Say, which of the sentences are in the Active and which are in the Passive Voice
- •Translate the sentences paying attention to the Sequence of Tenses
- •Translate the following Conditional sentences
- •Transformer Text a
- •Read and memorize words and word-combination
- •Make sure that you know these words and word combinations.
- •Read and translate the text.
- •Math the following English words with the Ukrainian ones.
- •Find English equivalents to the words:
- •Translate the word combinations from the text:
- •Answer the questions to the text.
- •Text b Operation at different frequencies
- •Read and memorize the words and word-combinations
- •Be sure that you know these words
- •Read and translate the text.
- •Text c Limitations
- •Make sure that you know these words and word combinations.
- •Read and translate the text.
- •Find the equivalents to the following.
- •Text d Construction
- •Read and memorise the words and word combinations
- •Read and translate the text. Cores
- •Find the equivalents to the folloving English words:
- •Point out English equivalents to the words:
- •Translate the word combinations.
- •Answer the questions.
- •Read the passage about steel cores. Retell it. Text e Windings
- •Listen to the words and word combinations from the text and memorize them.
- •Read and translate the text.
- •Match the English words and word combinations with the Ukrainian ones.
- •Insulation of windings
- •Text g Shielding
- •Supplement Speed control
- •Dc motor starters
- •Shielding
- •Autotransformers
- •Voltage transformers
- •Pulse transformers
- •3 Phase electrical power Transformer
- •3 Phase Transformer Delta and Wye Connections
- •Перелік скорочень
Shielding
Where transformers are intended for minimum electrostatic coupling between primary and secondary circuits, an electrostatic shield can be placed between windings to reduce the capacitance between primary and secondary windings. The shield may be a single layer of metal foil, insulated where it overlaps to prevent it acting as a shorted turn, or a single layer winding between primary and secondary. The shield is connected to earth ground.
Transformers may also be enclosed by magnetic shields, electrostatic shields, or both to prevent outside interference from affecting the operation of the transformer, or to prevent the transformer from affecting the operation of nearby devices that may be sensitive to stray fields such as CRTs.
Small signal transformers do not generate significant amounts of heat. Power transformers rated up to a few kilowatts rely on natural convective air-cooling. Specific provision must be made for cooling of high-power transformers. Transformers handling higher power, or having a high duty cycle can be fan-cooled.
Some dry transformers are enclosed in pressurized tanks and are cooled by nitrogen or sulphur hexafluoride gas.
The windings of high-power or high-voltage transformers are immersed in transformer oil — a highly refined mineral oil, that is stable at high temperatures. Large transformers to be used indoors must use a non-flammable liquid.
The oil cools the transformer, and provides part of the electrical insulation between internal live parts. It has to be stable at high temperatures so that a small short or arc will not cause a breakdown or fire. The oil-filled tank may have radiators through which the oil circulates by natural convection. Very large or high-power transformers (with capacities of millions of watts) may have cooling fans, oil pumps and even oil to water heat exchangers. Oil-filled transformers undergo prolonged drying processes, using vapor-phase heat transfer, electrical self-heating, the application of a vacuum, or combinations of these, to ensure that the transformer is completely free of water vapor before the cooling oil is introduced. This helps prevent electrical breakdown under load.
Oil-filled power transformers may be equipped with Buchholz relays which are safety devices that sense gas build-up inside the transformer (a side effect of an electric arc inside the windings), and thus switches off the transformer.
Experimental power transformers in the 2 MVA range have been built with superconducting windings which eliminates the copper losses, but not the core steel loss. These are cooled by liquid nitrogen or helium. Terminals. Very small transformers will have wire leads connected directly to the ends of the coils, and brought out to the base of the unit for circuit connections. Larger transformers may have heavy bolted terminals, bus bars or high-voltage insulated bushings made of polymers or porcelain. A large bushing can be a complex structure since it must provide electrical insulation without letting the transformer leak oil.
Enclosure Small transformers often have no enclosure. Transformers may have a shield enclosure, as described above. Larger units may be enclosed to prevent contact with live parts, and to contain the cooling medium (oil or pressurized gas).