1. INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING Sakarya Üniversitesi Teknoloji Fakültesi Elektrik Elektronik Mühendisliği Bölümü T4 Blok Introducing the department Introducing the EEE Engineering ethic Unit systems Direct and alternative current Resistor, capacitor, and coil Voltage and current supplies Ohm’s law, Kirchoff’s Laws Circuit concept, Serial, Parallel and Mixed circuits Semiconductor technology General Occupational Health and Safety Occupational Health and Safety in Electrical 1 Electrical and Electronics Engineering

2. INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING DIRECT AND ALTERNATIVE CURRENT 2 Electrical and Electronics Engineering The term DC is used to refer to power systems that use only one polarity of voltage or current, and to refer to the constant, zero-frequency, or slowly varying local mean value of a voltage or current. That is the direction and quantity according to the time is constant in DC. The generation and transmission of DC, which are difficult don’t preferred much. Batteries, cells, DC generators and DC power supplies can be given as example.

3. INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING DIRECT AND ALTERNATIVE CURRENT 3 Electrical and Electronics Engineering The current which its direction and quantity changes according to the time is called Alternative Current (AC). The basic structure of AC is a sinusoidal waveform. Electrical energy is produced as AC and DC. Today, more than 90% of electrical energy, consumed is produced as an alternative current. There are many reasons for that. First of all, to be able to economically carry the electrical energy too far there is a need for higher voltages. Otherwise, because of too much energy loss, the transmitted energy can not be sufficient for users. Also, DC generators can not be designed for high voltages.

4. INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING DIRECT AND ALTERNATIVE CURRENT 4 Electrical and Electronics Engineering DC generators, just produce up to 1500 V have been designed due to the difficulties of commutation (switching). On the contrary, such alternators can produce higher voltages such as 230, 6300, 10500 and 20000 V, it is also possible to increase these voltages up to 60 kV, 100 kV, and more by using a static machine, called transformator. Carrying the electrical energy is done by higher AC voltages. At the end of the transmission line, higher AC voltages are reduced to user voltage by transformators. It is possible to converting higher AC voltage to higher DC voltage with some rectifiers first, and then carrying the energy, and finally converting it to lower AC voltage with some inverters at the end of the line but these procedures can not be preferred. Powerful and high-speed generators can not be made because of the difficulties in commutation. Alternators can be made as powerful and high-speed. Thus, the energy cost per kilowatt hour and operating costs are lower.

5. INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING DIRECT AND ALTERNATIVE CURRENT 5 Electrical and Electronics Engineering Alternators can be made for 200000 kVA, 400000 kVA in power. At a constant speed in the industry, AC motor (induction motor) works more efficient than DC motor. Induction motor is more robust, and cheaper than DC motor, and its maintenance is also easy. The only advantage of the DC motor is that the speed can be set properly. The use of direct current is preferred, or where there is an obligation. DC can be used in electrical vehicles, metal plating, metal treatment, all electronic systems, and communications systems. In such these applications, DC can usually be obtained by converting from AC.

6. INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING DIRECT AND ALTERNATIVE CURRENT 6 Electrical and Electronics Engineering Production of AC

7. INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING DIRECT AND ALTERNATIVE CURRENT 7 Electrical and Electronics Engineering Wire moving in a magnetic field

8. INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING DIRECT AND ALTERNATIVE CURRENT 8 Electrical and Electronics Engineering Cycle and Period Alternance

9. INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING DIRECT AND ALTERNATIVE CURRENT 9 Electrical and Electronics Engineering The values of alternative current and voltage Maximum Value It is the biggest one of instantaneous values. Notice that, at the angle of 90 and 270 degrees, current reaches the maximum value.

10. INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING DIRECT AND ALTERNATIVE CURRENT 10 Electrical and Electronics Engineering The values of alternative current and voltage Average Value The average value is the average of instantaneous values in a cycle. Because of the number of positive instantaneous value in one cycle of alternating current is equal to the number of negative instantaneous value, the mean value in the alternating current is zero. For this reason, calculation of the average value is done by in one alternance only. If the maximum value is known, then the average value can be calculated as below: I ort = 0.636.I m

11. INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING DIRECT AND ALTERNATIVE CURRENT 11 Electrical and Electronics Engineering Effective Value (Root mean square) In physics it is a characteristic of a continuously varying quantity, such as a cyclically alternating electric current, obtained by taking the mean of the squares of the instantaneous values during a cycle. It is equal to the value of the direct current that would produce the same power dissipation in a resistive load. The RMS value of a continuous function or signal can be approximated by taking the RMS of a series of equally spaced samples. Additionally, the RMS value of various waveforms can also be determined without calculus. In the case of set of n values, the RMS The corresponding formula for a continuous function (or waveform) f(t) defined over the interval is,

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13. INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING DIRECT AND ALTERNATIVE CURRENT 13 Electrical and Electronics Engineering Period The period is the duration of time of one cycle in a repeating event, so the period is the reciprocal of the frequency. The period, usually denoted by T. The SI unit for period is the second. T = 1/f Frequency Frequency is the number of occurrences of a repeating event per unit time. For cyclical processes, such as rotation, oscillation, or waves, frequency is defined as a number of cycles per unit time. It is usually denoted by a Latin letter f. The SI unit of frequency is the hertz (Hz); one hertz means that an event repeats once per second.

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19. INTRODUCTION TO ELECTRICAL AND ELECTRONICS ENGINEERING DIRECT AND ALTERNATIVE CURRENT 19 Electrical and Electronics Engineering MULTIMETRE

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