VI. Translate the word combinations.
Typical laminated core; E-shaped and I-shaped pieces; triangular cross-section; static magnetic field; remanent magnetism; overcurrent protection device; power transmission line; long overhead power transmission line; transformer protection device; VHF band; effective gap width.
VII. Answer the questions.
1. What shape of pieces has a typical laminated core?
2. What fashion are the laminations stacked in?
3. How is a second gap formed between the E-pieces of the core?
4. Why are the E-pieces pressed together?
5. Is the effective gap width very large or very small?
6. What has the flux to do in order to work?
7. When does a saturation occur?
8. What will increase the overlap?
9. How can an air gap be created in that case?
10. In which way is the C-core made?
VIII. Read the passage about steel cores. Retell it.
Text E
Windings
I. Listen to the words and word combinations from the text and memorize them.
magnet wire –обмоточний провід (дріт)
coating –покриття
varnish –лак
synthetic –синтетичний
enamel –емаль
strip conductors –штабовий провідник (стрічковий)
heavy current –великий струм
strand –жила, скручувати
multiple-stranded conductor –багатожильний провід
power frequency –частота мережі
non-uniform –нерівномірний, неоднорідний
distribution –розподіл
arrange –розміщати
transposition –переміщення
equalize –вирівнювати
flexible –гнучкий
solid –твердий
winding –виток
external –зовнішній
connection –з’єднання, сполучення
tap –відгалуження, відвід
intermediate –проміжний
adjustment –регулювання
tap changer –перемикач вихідних обмоток трансформатора
on-load tap changer –перемикач вихідних обмоток трансформатора під напругою
switchgear –комутативний пристрій, розподільний пристрій
regulation – регулювання.
II. Read and translate the text.
The wire of the adjacent turns in a coil, and in the different windings, must be electrically insulated from each other. The wire used is generally magnet wire. Magnet wire is a copper wire with a coating of varnish or some other synthetic coating. Transformers for years have used Formvar wire, which is a varnished type of magnet wire.
The conducting material used for the winding depends upon the application. Small power and signal transformers are wound with solid copper wire, insulated usually with enamel, and sometimes additional insulation. Larger power transformers may be wound with wire, copper, or aluminium rectangular conductors. Strip conductors are used for very heavy currents. High frequency transformers operating in the tens to hundreds of kilohertz will have windings made of Litz wire to minimize the skin effect losses in the conductors. Large power transformers use multiple-stranded conductors as well, since even at low power frequencies non-uniform distribution of current would otherwise exist in high-current windings. Each strand is insulated from the other, and the strands are arranged so that at certain points in the winding, or throughout the whole winding, each portion occupies different relative positions in the complete conductor. This "transposition" equalizes the current flowing in each strand of the conductor, and reduces eddy current losses in the winding itself. The stranded conductor is also more flexible than a solid conductor of similar size is.
Windings on both the primary and secondary of power transformers may have external connections (called taps) to intermediate points on the winding to allow adjustment of the voltage ratio. Taps may be connected to an automatic, on-load tap changer type of switchgear for voltage regulation of distribution circuits.