Asymmetric Bypass Thyristors
The Dynex Bypass Thyristor range of devices is specially designed for the protection of IGBT modules in VSC multi-level applications, where a reduced forward blocking voltage is required.
The Dynex Bypass Thyristor
The primary characteristic of the bypass thyristor which determines current diversion from the IGBT diode is dynamic on-state voltage, with overall turn-on time a secondary influence. Highly optimised, Low FIT, low Vt, 3.3kV and 4.5kV bypass thyristor devices have been produced for VSC protection.
Correct design of the protective bypass thyristor provides greater flexibility to the system designer by allowing for greater compactness, better reliability and facilitating a push towards
higher scheme voltages.
Voltage Source Converter (VSC) technology provides a number of advantages over traditional (LCC) HVDC including self-commutation, small footprint, and black start capability and is becoming increasingly popular in applications such as offshore wind.With higher voltage systems, where the current handling capability of the IGBT diode is reduced, effective current diversion becomes essential.
VSC systems are vulnerable to DC faults, which cause a short circuit current to pass through the IGBT diode path. The magnitude of the fault current can be many times the rated current, can last for a number of cycles and can destroy the diode before an AC circuit breaker is able to clear the fault. Protection is required.
- Low dynamic on-state voltage for high-performance fault protection
- Enhanced surge rating
- High dV/dt capability >10kV/μs
- High di/dt capability
- Device can be switched from low anode-cathode voltage
- FIT rating is orders of magnitude lower than its IGBT companion