An overcurrent protection system is developed to ensure the safety of the gyrotrons in the electron cyclotron resonance heating system on the experimental advanced superconducting tokamak. Both the fast response overcurrent protection subsystem and the slow response overcurrent protection subsystem were developed. The current transformers were used as the current sensors in the fast response protection subsystem. The models of the current transformers and the superconducting magnet were built to analyse the effect of the environmental magnetic field on the current transformers using finite integration method. This analysis method is novel and the analysis results show that the current transformers should be placed at a distance >2.2 m from the magnet centre to ensure its normal work. The shunts were used to monitor the currents in the slow response protection subsystem. An anti-fuse FPGA and a timer is used to realise the signal processing in the fast protection circuit and the slow protection circuit, respectively. The response time of the fast protection circuit is <100 ns, and the response time of the slow protection circuit is <31 μs.

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Overcurrent protection for gyrotrons on the experimental advanced superconducting tokamak

References

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