Development of Quench Detection System for W7-X

Abstract

The Quench Detection System of W7-X will consist of nearly 400 Quench Detection Units (QDU) for the fast and reliable supervision of the 70 superconducting coils and the 120 superconducting bus bar sections. There will be five control racks with about 80 QDU, a data acquisition unit, an AC-DC power supply with integrated DC-UPS unit in each of the racks and a PC based data management system as an overlay structure. Each QDU will have a special analogue input circuit realised as a programmable half bridge front end with different polarity-sensing and limiting functions for suppressing high dynamic voltages. Special filter design is included for noise-suppression and over voltage protection. A reconfigurable control/arithmetic unit offers possibilities of future expansions (e.g. all digital evaluation). The QDU acquires and checks the differential voltages of the superconductors permanently. In case of a quench it triggers the fast discharge of the coils and the storage of the voltage signals on the memory unit. The quench signals are in the mV range and have to be clearly identified within a noisy and a high-voltage background within a few milliseconds. Each QDU transfers the stored signal dates via a high-speed RS-485 serial interface with 20KV optical isolation barrier to an industrial type data acquisition unit. A second optically isolated RS-485-network enables interconnection of each QDU in the control rack (Compound-Mode of QDU). The QDU are designed with an internal failsafe, programmable self test and redundancy feature, broken wire check of the quench detection cables and connectors inside and outside of the cryostat of W7-X. All QDU will be fed via an UPS supported 24V DC bus through a high voltage isolated DC-DC transformer on each unit. The design of the Quench Detection System allows operation under high voltage levels of up to 8kV and under magnetic stray field levels up to 30mT. The front end is very well isolated and the outputs of the QDU are strictly separated by optical isolating transformers. The differential inputs are equipped with 500V short-time over voltage protection. The paper will give an overview of the design of the first prototype.

The quench detection system of Wendelstein 7-X

“…Each subsystem generates two quench detection status signals and failure status signals, which coupled to two intelligent QD Interfaces, where the signals will be evaluated and processed, before the control of the main magnet power supply will initiate a fast or a slow discharge of the magnet system. The development of the Quench Detection Units (QDU) has been performed in cooperation between the MaxPlanck-Institut für Plasmaphysik Greifswald [1] and the Karlsruhe Institut of Technology (KIT), Institut für Prozessdaten-Verarbeitung und Elektronik. The manufacturing of nearly 580 series QDU was done by the company PRETTL Elektronik Lübeck, the manufacturing of the series backplanes is right under way by the company Dresden Elektronik.…”

Wendelstein 7-X – a Technology Step towards Demo

“…Each power supply delivers a direct current of up to 20 kA at a voltage of up to 30 V. This system has undergone the final acceptance tests and has proven that the output currents can be stabilized to the required accuracy of 2 × 10 −3 [11]. The quench detection system, developed in co-operation with FZK, will consist of almost 400 quench detection units that check permanently the differential voltages between double-layers of all coils and between all sectors within the bus-bar system [12]. The prototype units have been tested successfully and series production will start soon.…”

RS-485 Bus Design of a Missile Simulation Training System

“…In recent years, RS-485/422 [1][2], CAN-bus [3], PROFIBUS [4][5] and other bus are used in distributed system in China [6][7]. RS-485 bus and CAN bus adopt twisted-pair transmitting balanced differential signals, so it can get good ability of transmission distance, data rates and anti EMI (Electro Magnetic Interrupt).…”