III. Match the English words and word combinations with the Ukrainian ones.

strand –перемикач вихідних обмоток трансформатора

magnet wire –штабовий провідник

heavy current –регулювання

coating –емаль

enamel –лак

transposition –вирівнювати

switchgear –комутаційний пристрій

varnish –покриття

intermediate –переміщення

adjustment –великий струм

equalize –проміжний

strip conductors –обмоточний провід

tap changer –жила.

IV. Read the text and find English equivalents to the words:

виток, розміщати, нерівномірний, гнучкий, регулювання, твердий, з’єднання, розподіл, ізолювати, зовнішній.

V. Translate the word combinations.

very heavy currents; high frequency transformers; skin effect losses; multiple-stranded conductors; low power frequency; high-current windings; on-load tap changer; voltage regulation; distribution circuit.

VI. Answer the questions.

1. What kind of wire is generally used for windings?

2. What does the conducting material used for windings depend on?

VII. Comment on wires used for:

small power transformers;

larger power transformers;

very heavy currents;

high frequency transformers.

VIII. Find the wrong statement.

1. Primary and secondary windings of power transformers may have external connections.

2.Primary and secondary windings of power transformers may have internal connections.

Text F

Insulation of windings

I. Read and translate the text. Pay attention to the words given below.

layer –шар

immerse –занурювати

transformer oil –трансформаторне масло

corona discharge –коронний розряд

capability –здатність

deteriorate –погіршувати

casing –корпус

seal –герметизувати

moisture –волога

ingress – доступ

medium –середовище

epoxy resin –епоксидна смола

impregnate –просочувати, промочувати

dirt –бруд

damp –волога

environment – середовище.

The turns of the windings must be insulated from each other to ensure that the current travels through the entire winding. The potential difference between adjacent turns is usually small, so that enamel insulation is usually sufficient for small power transformers. Supplemental sheet or tape insulation is usually employed between winding layers in larger transformers.

The transformer may also be immersed in transformer oil that provides further insulation. Although the oil is primarily used to cool the transformer, it also helps to reduce the formation of corona discharge within high voltage transformers. By cooling the windings, the insulation will not break down as easily due to heat. To ensure that the insulating capability of the transformer oil does not deteriorate, the transformer casing is completely sealed against moisture ingress. Thus the oil serves as both a cooling medium to remove heat from the core and coil, and as part of the insulation system.

Certain power transformers have the windings protected by epoxy resin. By impregnating the transformer with epoxy under a vacuum, air spaces within the windings are replaced with epoxy, thereby sealing the windings and helping to prevent the possible formation of corona and absorption of dirt or water. This produces transformers suitable for damp or dirty environments, but at increased manufacturing cost.

II. Answer the questions.

1. Must the turns of the windings be insulated from each other? Why?

2. Is the enamel insulation sufficient for small power transformers?

3. What is usually employed between winding layers in larger transformers?

III.Comment on transformer oil functions.

IV. Speak on the alternative protection of the transformer windings by epoxy resin.

Text G

Shielding