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COTS Circuit Predicting Coil Zero-Current Crossing for Early Thyristor Triggering in a Fast, High-Power Magnetic Generator
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| Author(s) |
R. Charlet de Sauvage; Ph. Dondon; I. Lagroye; B.Veyret |
| Abstract |
This paper describes the design and construction of a zero-current crossing detection circuit for a high-power (6000 A,
650 V) magnetic generator delivering short (340 μs), high-intensity (2 Tesla) pulses, used to stimulate living tissues. The magnetic pulses are produced by discharging a capacitor Cd into a coil in resonant mode. Half-sine or full-sine waveforms may be selected. When full-sine current into the coil is selected, a smooth transition between the 2 half-sines is required to ensure continuity in tissue excitation, i.e. the second thyristor must be triggered shortly before the first one
switches off. The operating theory is to compute the period of the resonant circuit in advance, irrespective of interchangeable
coil inductance and damping factors. The system core consists of a toroid sensor encircling the high-current main wire of the coil and an integrator circuit that is switched on or off by three events: the starting time and zero-crossing time of the sensor voltage and the zero-crossing time of the potential across Cd. This makes it possible to detect the pulse period right from the end of the first quarter period. Details of the robust COTS (commercial off-the-shelf) electronic
design are given. Electric tests fully validated this design. The final section discusses the results and possible improvements. |
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| Filename: | Unnamed file |
| Filesize: | 357.4 KB |
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| Type |
Members Only |
| Date |
Last modified 2011-11-29 by System |
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