Inverter with overvoltage protection

摘要

A DC-AC inverter (7) with overvoltage protection connected to the pantograph (2) of an overhead conductor-supplied tram has a choke (5) and condenser (6) as an input filter. There is a parallel circuit comprising a thyristor (9), a resistance (10) and a diode (13), all in series with the choke. There is also a parallel branch to the condenser, comprising a second resistance (11) in series with a second thyristor (12).In normal operation, the first thyristor is switched on, and the second one is off. However, the states reverse when an external voltage spike constituting an over-voltage is present. There may be a rapid-acting circuit-breaker between the parallel circuit and the input lead from the pantograph.