22-06-2012, 04:20 PM
Design, Development, Manufacturing and Testing of a 10 Stage 50kV High Voltage Impulse Generator
50kV High Voltage Impulse Generator.docx (Size: 1.48 MB / Downloads: 50)
An impulse generator is an electrical apparatus which produces very short high-voltage or high-current surges. Such devices can be classified into two types: impulse voltage generators and impulse current generators. High impulse voltages are used to test the strength of electric power equipment against lightning and switching surges. Also, steep-front impulse voltages are sometimes used in nuclear physics experiments. High impulse currents are needed not only for tests on equipment such as lightning arresters and fuses but also for many other technical applications such as lasers, thermonuclear fusion, and plasma devices.
Marx generator
One form is the Marx generator, named after E. Marx who first proposed it in 1923. It is a mechanical arrangement of the triggering circuit (spark gap), the DC supply, capacitors and resistors. This consists of multiple capacitors that are first charged in parallel through charging resistors by a high-voltage, direct-current source and then connected in series and discharged through a test object by a simultaneous spark-over of the spark gaps. The impulse current generator comprises many capacitors that are also charged in parallel by a high-voltage, low-current, direct-current source, but it is discharged in parallel through resistances, inductances, and a test object by a spark gap. A Marx generator is shown in the below figure.
Principle
A number of capacitors are charged in parallel to a given voltage, V, and then connected in series by spark gap switches, ideally producing a voltage of V multiplied by the number, n, of capacitors (or stages). Due to various practical constraints, the output voltage is somewhat less than n×V. For generating the impulse voltages, the generator capacitance (C1) is charged and then discharged into the wave shaping network. This produces the high voltage that is to be generated. In order to generate very high voltages, a single capacitor/the charging unit becomes large and economically inefficient. Hence the multi stage impulse generator or the Marx generator.