Siemens’ new generation of lightrail vehicles is being introduced around the world. First locations that will see these fully automated vehicles in operation are the city of Rennes and Bangkok airport.
Traction inverters are one of the core systems on board a train. Siemens wants to have a technically strong and reliable partner to provide modern power electronic equipment. A partner willing and able to develop quality systems, willing to customise and able to competitively produce large and small series. The high safety demands for this crucial system further narrowed the choices for Siemens.
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Strukton developed a compact traction inverter that powers the permanent magnet motors.
The 750Vdc input voltage is converted to 2×3 phase AC voltage to drive two Permanent Magnet (PM) motors. For this, 4 Power Modules (type 2N17-250) generate 8 phases. 6 legs for driving, 2 legs for dissipating brake energy if needed.
The Power Module is a natural air-cooled and self-protected module (170kW in braking). The phase inductance of the PM motor is very low. To minimise the ripple of the motor current, a high switching frequency is necessary. High switching frequency auxiliary IGBTs are used to ease the main IGBTs from switching losses. With this topology, the main IGBT switches on without current and switches off without voltage.