For the fulfillment of these objectives, INDAELTRAC has developed a concept that is based on the use of the modern IGBT transistors, keeping the continuous current engines. One will obtain, in this way, an easier electric drives, very compact and which offers a very precise continuous electronic control, without stages, implicitly without current leaps that will produce mechanic shocks.
The elimination of the electric resistances from the power electronics circuit and their replacement with the choppers actually represent the elimination of the loses through the heat dissipation, especially at reduced speed, which is characteristic to the urban traffic.
Moreover, the chopper driving allows to the continuous current motor to pass in a generator regime, especially when it brakes. So, the kinetic energy of the tramway is transformed in electric energy that is recovered in the power line. This energy is consumed by the other vehicles that are powered from the same line. In the case in which there are no other consumers, the braking energy will be dissipated on a resistance.
Another advantage offered by the use of the chopper is the elimination of an important number of electromagnetic contactors from the old wired circuit. In the electrical scheme there were kept only the contactors that change the sense which are (anyway) rarely controlled (when going backwards). The commutation between running regime and brake regime, which is frequently used, is made with IGBT transistor.
In this way, due to the net superior reliability of the IGBT transistors compared to the electromagnetic contactors, the chopper modernization increases the reliability of the vehicle and reduces the costs and the maintenance time.
The continuous electronic control of the current respectively of the motor torque and verry fast electronic protections realized with the chopper lead on one hand to the increase of the reliability and on the other hand to the increase of the safety in the exploitation of the modern vehicle.
The modernization of the electrical traction vehicles supposes the replacement of the motor-generator group for the power supply of the auxiliary services with a static converter and the management, command and the control of the entire vehicle by a board computer. The board computer offers a diagnosis system that, with the help of a PC, offers the possibility of the visualization of the measurements and relevant data and faults as well as their localization.
In a normal function regime the chopper is controlled by the board computer through the CANopen bus. For an easier troubleshooting, the command module of the chopper has an isolated communication port, through which the data packages are being sent to a terminal (usually a personal computer). The data sent can be seen on-line, they can be stored for an ulterior analysis.