III Answer the following questions:

1. What is smoothing circuit?

2. What will reduce ripple?

3. How can the number of peaks be affected by?

4. What does a full wave recifier achive?

5. What does the choke present?

6. When will a voltage regulator be used?

IV Give the equivalents of the following words:

напруга, досягати, замість, потребувати, вміщувати, поєднувати, використання, забезпечувати.

V Use the correct tense form of the verbs and translate into Ukrainian:

1. Electricity (to be) a subject of scientific interest since at least the early 17^th century.

2. The first electrical engineer (to be) probably William Gilbert who designed the versorium: a device that detected the presence of statically charged objects.

3. During the development of radio, many scientists and inventors (to contribute) to radio technology and electronics.

4. James Clerk Maxwell (to publish) a unified theory of electricity and magnetism in his treatise on Electricity and Magnetism.

5. The Darmstadt University of Technology (to found) the first chair and the first faculty of electrical engineering woldwide in 1882.

VI Translate the text in writing:

Voltage-doubling rectifiers

The simple half wave rectifier can be built in two versions with the diode pointing in opposite directions, one version connects the negative terminal of the output direct to the AC supply and the other connects the positive terminal of the output direct to the AC supply. By combining both of these with separate output smoothing it is possible to get an output voltage of nearly double the peak AC input voltage. This also provides a tap in the middle which allows use of such a circuit as a split rail supply.

A variant of this is to use two capacitors in series for the output smoothing on a bridge rectifier then place a switch between the midpoint of those capacitors and one of the AC input terminals.

With the switch open this circuit will act like a normal bridge rectifier with it closed it will act like a voltage doubling rectifier. In other words this makes it easy to derive a voltage of roughly 320V (+/- around 15%) DC from any mains supply in the world, this can then be fed into a relatively simple switched mode power supply.

Unit 8 Applications

I Read and remember the following words:

1. remove – видалити

2. derive – одержувати, виводити

3. fan – вентилятор

4. find – знаходити

5. amplify – посилювати

6. drop – падіння

7. demodulation – демодуляція

8. match – підходити, підбирати

9. capacitance – ємкість

10. welding – зварювання

11. hardware – апаратне забезпечення

II Read and translate the following text:

A rectifier diode (silicon controlled rectifier) and associated mounting hardware. The heavy threaded stud helps remove heat.

The primary application of rectifiers is to derive usable DC power from an AC supply. Virtually all electronics except simple motor circuits such as fans require a DC supply but find uses inside the power supplies of virtually all electronic mains power is AC so rectifiers equipment.

Converting DC voltage from one level to another is much more complicated. One method of such DC-to-DC conversion is to first convert to AC (using a device called an inverter), then use a transformer to change the voltage, and finally rectify it back to DC.

Rectifiers also find a use in detection of amplitude modulated radio signals. The signal may or may not be amplified before detection but if unamplified a very low voltage drop diode must be used. When using a rectifier for demodulation the capacitor and load resistance must be carefully matched. Too low a capacitance will result in the high frequency carrier passing to the output and too high will result in the capacitor just charging and staying charged.

R ectifiers are also used to supply polarised voltage for welding. In such circuits control of the output current is required and this is sometimes achieved by replacing some of the diodes in bridge rectifier with thyristors, whose voltage output can be regulated by means of phase fired controllers.