Principle

Insulated Gate Bipolar Transistors (IGBTs) are today's state-of-the-art power electronics for the traction system of electric (and diesel-electric) rail vehicles. They replace the previous inverter generation represented by GTO (gate turn-off thyristors).

In contract to conventional transistors, IGBTs operate at very high currents (> 1000 A). The principle benefit of IGBTs over GTOs is a much (3 to 4 times) higher switching frequency. This reduces the current required and therefore the heat generated, giving smaller and lighter units. The high switching frequencies also smoothen the acceleration process and reduce the traction noise.

Fields of application

Power electronics based on IGBTs are used in a number of fields in industry and transportation.

Improved traction efficiency

According to an expert from Bombardier, the efficiency of the IGBT at payload is about 5 - 6% better than the efficiency of the GTO (95% vs. 90 % efficiency). The effect on energy efficiency in real operation maybe even bigger due to the fact that the relative advantage of IGBTs over GTOs is even higher at low loads. This may push the efficiency gain even beyond 10%. for instance, Japanese JR Hokkaido claims that IGBT controlled 3-phase AC motors save 15 % energy compared to their GTO predecessors.

Mass reduction

IGBT modules are generally lighter than GTO modules (some 30%). This may offer constructive advantages but is negligible for energy efficiency.

Noise reduction

Japanese JR Hokkaido claims that IGBT controlled 3-phase AC motors reduce noise by 10% compared to their GTO counterpart.