Essay: High Voltage Development

LITERATURE REVIEW
High voltage engineering is not only a key technology for a safe, economic and sustainable electric power supply. Furthermore, a broad spectrum of applications includes most of the innovative fields in engineering and science, such as medical, engineering, laser technology, industrial production, automotive engineering, food technology, Bioengineering, nanotechnology, environmental protection, recycling, electromagnetic compatibility, scientific research or superconductivity [4].
Electric arc being complex phenomenon, depends on many factors, for instance the electrode gap space, electrode material, humidity etc [2]. The effect of pulsed electrical discharge such like a shock wave, electromagnetic radiations, ozone and free radicals lead to hematological changes; increase in erythrocytes, the effects of the discharge can also be seen in rising rates of hemoglobin, increase in white blood cells, decrease in lymphocytes and increasing of thrombocytes [5].
2.2. Transformer
A transformer is an electrical device constructed of two or more coils of wire (windings) magnetically coupled to each other so that there is a mutual inductance for the transfer of power from one winding to the other. Although many transformers have more than two winding, the coverage in this section is restricted to a basic two winding transformer [6].
The main function of power transformer is to step up or step down the voltage [1]. A transformer consists of two or more coils that are magnetically couple as shown in Figure 2.2. There are some differences in the functions of power transformer and flyback transformer. The flyback transformer has three functions which are step up and down voltage, stored the energy in magnetizing inductance (Lm) and transfer the energy from primary side to secondary side. The circuit diagram for flyback transformer is shown in Figure 2.3. The principle of this transformer is the current will enter the dotted terminal in primary and must exit at dotted terminal in secondary.
The typical operating current output of FBTs is extremely low, whereas it will be in the range of milliamps. The high frequencies essentially make it necessary to construct a supplementary complicated control circuit [3].
By referring to the Figure 2.1, the Common core used for the transformer is ferrite type. The number of turns in the primary and secondary is limited to the size of the core. The number of turns in the primary and secondary side of the transformer is determined by the standard wire gauge of the conductor to be used. The core is specifically designed for frequency capability. Ferrite is the best choice in high frequency transformer. [3]
The duty cycle loss due to this resonance is a severe the problem with such high output voltage applications. The first requirement of a flyback converter used in low power level high output voltage applications is that the output voltage should be obtained as the expected value [7]. An electric arc which is nothing but an electric discharge happened when electric-field between two conductors exceeds the breakdown strength of the air or other medium in the space between the electrodes, is considered a source of harmonics [8].
Figure 2.1 Skematic for hr7505[8]
Figure 2.2 Cross-section of transformer [3]
Figure 2.3 Flyback Transformer circuit with magnetizing inductance [3]
2.3 Metal Oxide Semiconductor Field Effect (MOSFET) IRF460
There are many types of power semiconductor switches that can be choose to control the circuit. In this project, Metal Oxide Semiconductor Field Effect (MOSFET) has been chosen as the switch to control the ON and OFF state. The symbol for N – channel MOSFET and the i-v characteristics for n-channel MOSFET are shown as Figure 2.4 and Figure 2.5.
Figure 2.4 Symbol for N-Channel MOSFET [9]
Figure 2.5 i-v characteristic [9]
MOSFET are available for voltage ratings in 1000V and for current ratings, it is available in the range from 30A until 50A. For switching, the devices should satisfy the 3 important parameters which are power, voltage and current ratings of the converter. The advantage of MOSFET compare to other device is the short switching time, which in the range of nanoseconds [7]. Hence, the switching losses is small and high efficiency can be achieves. To switch ON and OFF, the pulse need to be supply to get pin of the MOSFET. So, Pulse Width Modulation (PWM) is used to supply the pulse and start to operate the MOSFET [7].
2.4 Arduino Uno
Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software [10]. Arduino can sense the environment by receiving input from a variety of sensors and can affect its surroundings by controlling lights, motors, and other actuators. The microcontroller on the board is programmed using the Arduino programming language and the Arduino development environment. Arduino projects can be stand-alone or they can communicate with software running on a computer. Figure 2.6 shown the board of arduino uno system from the point of view of the top and bottom.
Figure 2.6 Arduino Uno [10]
2.5 Heat Sink
Heat sink is a component which can keep the other component or device from burning up [7]. When the power supply is supplied the voltage to the circuit, the component and device which connected will be heat up. If the heat cannot be removing from the device, the circuit may be failing to operate after a period of time due to the damaged of the device. So, it is important to any circuit to provide the cooling path to the device to avoid the failure as illustrate in Figure 2.7. Moreover, the heat sink can be transform to equivalent circuit as show in Figure 2.8 for design purpose.
Figure 2.7 Cooling Path provide by heat sink [7]
Figure 2.8 Equivalent circuits for heat sink [7]