• Some of the main advantages that lead implicitly to the idea of the modernization of the vehicles with electric traction are:
  • - saving enerrgy use with up to 40%;
  • - the increase of the reliability;
  • - the maintenance reduction;
  • - the increase of safety in exploitation and in passengers comfort;
  • - the fulfillment of the requirements of a modern electrical drives used in the urban public transport.

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.

• Some of the main functions of the chopper are:
  • - provides power supply for the driving motors corresponding to the run-brake regime;
  • - unitary construction, mono-block;
  • - CANopen communication with the board computer for receiving the commands and the permanent monitoring of the tramway's state;
  • - the chopper can function in a fault regime if the board computer is damaged or communication is lost; this regime is useful todrive the vehicle to the depot for troubleshooting;
  • - the command module of the chopper can store information that can easily be used for the maintenance of the vehicle (function hours, mileages, maximum speed, minor faults or critical faults, etc.).
• Traction control chopper with IGBT
  • Input voltage: 750VDC / 600VDC (+20%;-30%)
  • Output: 150KW
  • Construction: modular
  • Location: under floor or on the roof
  • Cooling: forced ventilation
  • Caracteristics - IGBT-technology; without contactors to change the start - brake mode, combined egenerative and rheostatic brake, control signal: optical fibre, protections: overtension, short-circuit, overtemperature
  • Control unit with DSP:
    • Construction: PBB boards, plug-in unit
    • Cooling: natural convection
    • Supply: 24VDC (+/- 20%)
• Auxiliary power supply static converter
  • Nominal output power: 5KVA
  • Input voltage: 750VDC(+20%;-30%)
  • Output voltage: 24-30VDC adjustable
  • Maximum output 180ADC
  • Options:
    • Output: Treephase voltage 400VAC, 50Hz
    • Nominal power: on request