Beginning with 1996 INDAELTRAC has designed and produced chopper drive equipment for the trolley buses made in Romania and afterwards for the updating of the trolley-buses in operation at various transport administrations throughout the country.

The first equipment produced for E312 trolley was a chopper with GTO and analogical control.

The equipment made for E 412 and E 512 trolley buses were with IGBT chopper with micro-controller control and static source for auxiliary supply.

The trolley bus is driven by a DC series excitation motor which develops a motor couple proportional to the current value through the motor.

The current average value by the traction motor is assigned by the travel pedal and it is maintained at this level by the regulating diagram on the travel regime.

By braking, the current assignment is done by the braking pedal but the electronic control plug-in unit maintains the current at this value by the motor and the voltage in the intermediate diagram is maintained within the permissible limits. In this regime the motor works like a generator. The breaking is regenerating if the circuit permits (trolley buses are running), otherwise the braking is rheostatic but also at the prescribed braking current.

By the IGBT chopper progressively the voltage in the supply circuit is passed to the traction motor which transforms it in mechanical power to the trolley bus wheels being also monitored the current by the motor not to exceed the maximum permissible values.

The electronic control plug-in unit avoids the indecision that should appear by the simultaneous depressing of the two pedals (travel and braking) by the priority to the brake. After the braking pedal returns in “STOP” position the travel regime resume is possible by actuating the travel pedal.

The reverse of the travel (reverse travel) is done from the driver’s cab but only when the vehicle is stopped.In this regime the run maximum current is limited at 50% of the forward run current (the maximum speed of the trolley bus is 30 km/h).