III Answer the following questions:

1. What is rectifier?

2. What do all rectifiers comprise?

3. What can you tell about a half-wave rectifier?

4. What does full-wave rectification convert?

5. What are called bridge rectifier?

IV Give the equivalents of following words:

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

V Translate into Ukrainian:

1. Electrical engineering – sometimes refered to as electrical and electronic engineering – is an engineering field that deals with the study and application of electricity, electronics, electromagnetism.

2. The field fist became an identifiable occupation in the late nineteenth century after commercialization of the electric telegragh and electrical power supply.

3. The field now covers a range of sub-studies including power, electronics, control systems, signal processing and telecommunications.

4. Electrical engineering may or may not encompass electronic engineering.

5. Where a distinction is made, electrical engineering is considered to deal with the problems associated with large-scale electrical systems such as power transmission and motor control.

VI Translate the text in writing:

While PALs were busy developing into GALs and CPLDs (all discussed above), a separate stream of development was happening. This type of device is based on gate array technology and is called the field-programmable gate array (FPGA). Early examples of FPGAs are the 82s 100 array, and 82S105 sequencer, by Signetics, introduced in the late 1970s. The 82S100 was an array of AND terms. The 82S105 also had flip flop functions.

FPGAs use a grid of logic gates, similar to that of an ordinary gate array, but the programming is done by the customer, not by the manufacturer. The term "field-programmable" means the array is done outside the factory, or "in the field."

FPGAs are usually programmed after being soldered down to the circuit board, in a manner similar to that of larger CPLDs. In most larger FPGAs the configuration is volatile, and must be re-loaded into the device whenever power is applied or different functionality is required. Configuration is typically stored in a configuration PROM or EEPROM. EEPROM versions may be in-system programmable (typically via JTAG).

FPGAs and CPLDs are often equally good choices for a particular task. Sometimes the decision is more an economic one than a technical one, or may depend on the engineer's personal preference or experience.

Unit 7 Rectifier output smoothing

I Read and memorize the following words:

1. smoothing – рівність

2. suffice [sə΄faıs] – задовольняти

3. to deliver – поставляти

4. capacitor – конденсатор

5. ripple – круг, коло

6. tolerable – виносливий

7. frequency – частота

8. affect – впливати

9. peak – пік

10. choke – заглушка

11. impedance – опір

II Read and translate the text:

While half- and full-wave rectification suffice to deliver a form of DC output, neither produces constant-voltage DC. In order to produce steady DC from a rectified AC supply, a smoothing circuit, sometimes called a filter[1], is required. In its simplest form this can be what is known as a reservoir capacitor, Filter capacitor or smoothing capacitor, placed at the DC output of the rectifier. There will still remain an amount of AC ripple voltage where the voltage is not completely smoothed.

Sizing of the capacitor represents a tradeoff. For a given load, a larger capacitor will reduce ripple but will cost more and will create higher peak currents in the transformer secondary and in the supply feeding it. In extreme cases where many rectifiers are loaded onto a power distribution circuit, it may prove difficult for the power distribution authority to maintain a correctly shaped sinusoidal voltage curve.

For a given tolerable ripple the required capacitor size is proportional to the load current and inversely proportional to the supply frequency and the number of output peaks of the rectifier per input cycle. The load current and the supply frequency are generally outside the control of the designer of the rectifier system but the number of peaks per input cycle can be affected by the choice of rectifier design.

A half-wave rectifier will only give one peak per cycle and for this and other reasons is only used in very small power supplies. A full wave rectifier achieves two peaks per cycle and this is the best that can be done with single-phase input. For three-phase inputs a three-phase bridge will give six peaks per cycle and even higher numbers of peaks can be achieved by using transformer networks placed before the rectifier to convert to a higher phase order.

To further reduce this ripple, a capacitor-input filter can be used. This complements the reservoir capacitor with a choke and a second filter capacitor, so that a steadier DC output can be obtained across the terminals of the filter capacitor. The choke presents a high impedance to the ripple current.[2]

If the DC load is very demanding of a smooth supply voltage, a voltage regulator will be used either instead of or in addition to the capacitor-input filter, both to remove the last of the ripple and to deal with variations in supply and load characteristics.