Imperial Journal of Interdisciplinary Research (IJIR) Vol-3, Issue-4, 2017 ISSN: 2454-1362, http://www.onlinejournal.in Marx Generator Based High Voltage Using MOSFETs: A Review Mr. Abhishek Gupta1, Ms. Nikita Mittal2, Sourav Gurjar3, Subham Kumar Jalan4, SumitTalwani5, Suraj Singh Mehta6 1,2 Assistant Professor, Department of Electrical Engineering, SKIT, Jaipur 3,4,5,6 Student, Department of Electrical Engineering, SKIT, Jaipur Abstract-This paper shows the development of a Accordingly, it is compulsory to test high voltage reliable and easy to carry compact 4 stages Marx (HV) apparatus during its making stage. Power Generator that can produce impulse voltage 4 system protection is an important thing for the times of input voltage with some minor losses. In maintained service of the electrical power system. addition, three different experimental circuits of Normally the protection of electrical power DC supplies have been made. The highest output depends on the performance of insulation systems was 100 V DC for which input was taken as the under transient over voltage conditions arises due main supply for the experimental and simulated to switching applications andlightning. Transient Marx generator circuit. This generator is useful in over voltages along with the abrupt changes in the small scale industries and academic institutions to state of power systems, e.g. switching operations or demonstrate impulse voltages and also to perform faults are known as switching impulse voltages and testing on insulators and transformers of lower that due to lightning are known as lightning rating in laboratory. A total of 4 stages of both impulse voltages. It has become generally simulated, experimental Marx impulse generator identified that switching impulse voltages are circuit is designed and the impulse waves are usually the prevalent factor affecting the design of recorded. The simulated recorded impulse insulation in HV power systems for rated voltages waveform, is compared with the standard impulse of about 300 kV and above. So attention is required wave. Both of circuits, the efficiency of each stage for these two types of over voltages. Hence in order was calculated and the percentage of error in the to protect these equipments a prototype of the same front and tail time was also found out as well as the can be used to test against lightning strikes. effects of the circuit parameters on the impulse waveform characteristics were also studied. The A Marx Impulse generator is able to generate simulation was done with the help of Proteus 8 lightning impulse voltage. This generator consists Professional. In this work, the comparison in terms of multiple capacitors that are first charged in of magnitude of the experimental and simulated 4 parallel through charging resistors by a high- stages Marx generator circuit has been carried out. voltage, direct-current source and then connected in series and discharged through a test object by a 1. INTRODUCTION concurrent spark-over between the sphere gaps. The generated voltage from impulse generator must Various high voltage equipments such as surge satisfy the standard values of voltage defined by the arresters, power transformers, circuit breakers, high International Electro techno Commission in order to tension transmission line towersandisolators are qualify as a standard impulse voltage that can be present in transmission substations. Since these used for testing purposes. The standard methods of kind of equipments are so costly also important for measurement of high-voltage and the basic methods maintaining continuous power supply, there for application of all types of apparatus for direct protection should be the higher priority for an voltages, alternating voltages, switching impulse electrical engineer. These equipment should not voltages and lightning impulse voltages are laid only tolerate the rated voltage which is the highest down in the important national and international voltage of a system, but also over voltages. standards. In this work, an attempt has been made to develop a made practically. In addition, three different sorts of compact, inexpensive, portable 4 stages Marx HV DC supply were made to test the practical impulse generator circuit for demonstration of high circuit as well as to provide HV DC supply in voltage impulses in academic institutions. This 4 laboratory. Finally, the simulated and experimental stages Marx generator circuit, was simulated by results were compared in terms of their magnitudes. using PROTEUS software and the same circuit was Imperial Journal of Interdisciplinary Research (IJIR) Page 1522 Imperial Journal of Interdisciplinary Research (IJIR) Vol-3, Issue-4, 2017 ISSN: 2454-1362, http://www.onlinejournal.in 2. PROJECT OBJECTIVES V, so they all behave as open circuits while the capacitors charge. The last gap isolates the output i. To design 4 stage Marx Generator circuit of the generator from the load; without that gap, using PROTEUS software to generate a the load would prevent the capacitors from waveform of impulse voltage. charging. To create the output pulse, the first spark gap is caused to break down (triggered); the ii. To provide different kinds of high voltage DC breakdown effectively shorts the gap, placing the supply in HVE laboratory. first two capacitors in series, applying a voltage of iii. To compare the theoretical values of peak about 2V across the second spark gap. voltage obtained in simulation with those Consequently, the second gap breaks down to add recorded in practical circuit. the third capacitor to the stack, and the process continues to sequentially break down all of the gaps. The last gap connects the output of the series 3. MULTI STAGE MARX IMPULSE stack of capacitors to the load. Ideally, the output CIRCUIT voltage will be nV, the number of capacitors times the charging voltage, but in practice the value is Due to the difficulties experienced in very high less than expected because of losses. voltage switching of the spark gap, increase in circuit element size, need of high direct current Voltage Doubling Principle:- voltage to charge capacitor and difficulties in corona discharge suppression from the structures In this paper, the main concept of this work is to during charging period the extension of the single study the voltage doubler circuit based on stage to multistage impulse generator is made. simulation and hardware implementation and finally based on CockcroftWalton (C-W) voltage A multistage generator is developed by cascading multiplier circuits to fabricate a DC power supply smaller single stage to generate high magnitude of in the laboratory. The conventional technique is output voltage. used because the designed multiplier circuit is intended to be applied for impulse generator The primary requirement is to charge capacitors charging units. The main components of the DC through the rectifier circuit and when all the power supply are rectifier diodes and capacitors. capacitor reaches to the fully charged state then The simplest unregulated power supply consists of spark gaps are allowed to break down causing the three parts namely, the transformer unit, the capacitors to add in series. As a result the nominal rectifiers unit and the capacitors unit. output voltage is equal to the input voltage Figure 1 shows the schematic for a half-wave multiplied by the number of stages in the impulse voltage doubler. In fact, the doubler shown is made generator circuit. At first, n capacitors are charged up of two half-wave voltage rectifiers. Here C and in parallel to a voltage (V) by a high voltage DC 1 D make up one half-wave rectifier and C and D power supply through the resistors. The spark gaps 1 2 2 make up the other rectifier. used as switches have the voltage V across them, but the gaps have a breakdown voltage greater than Figure 1: Voltage Doubling Circuit. Imperial Journal of Interdisciplinary Research (IJIR) Page 1523 Imperial Journal of Interdisciplinary Research (IJIR) Vol-3, Issue-4, 2017 ISSN: 2454-1362, http://www.onlinejournal.in 4. IMPLEMENTATION OF 4 STAGE current flows with no significant change in voltage, MARX GENERATOR then the (simplified) working of the cascade is as follows: The circuit generates a high-voltage pulse by charging a number of capacitors in parallel, then 1. Negative peak (−Us): The C1 capacitor is suddenly connecting them in series. See the Figure charged through diode D1 to 3.1. At first, n capacitors (C) are charged in parallel Us V (potential difference between left to a voltage V by a high-voltage DC power supply and right plate of the capacitor is Us) through the resistors (RC). The spark gaps used as 2. Positive peak (+U ): the potential of switches have the voltage V across them, but the s C1 adds with that of the source, thus gaps have a breakdown voltage greater than V, so charging C to 2U through D they all behave as open circuits while the 2 s 2 3. Negative peak: potential of C has capacitors charge. The last gap isolates the output 1 dropped to 0 V thus allowing C to be of the generator from the load; without that gap, 3 charged through D to 2U . the load would prevent the capacitors from 3 s charging. To create the output pulse, the first spark 4. Positive peak: potential of C2 rises to gap is caused to break down (triggered); the 2Us (analogously to step 2), also charging breakdown effectively shorts the gap, placing the C4 to 2Us. The output voltage (the sum of voltages under C and C ) rises until first two capacitors in series. 2 4 4Us is reached. The above voltage quadrupler circuit uses In reality more cycles are required for C to reach minimum components to approximately multiply 4 the full voltage. Each additional stage of two (quadrupler) the AC voltage (Vin) across the input diodes and two capacitors increases the output terminals.