After 1990 the transport administration of Romanian cities bought KT4D trams manufactured between 1970-1980.

The trams adaptation to the power supply of 750V which is the most used in Romania is difficult to be achieved and it is done with an additional energy consumption.

Therefore, is required the electronic equipment using both for the traction part and for the auxiliary power supply.

INDAELTRAC S.A offers choppers for the traction part by keeping the existing motors and the static converter for the auxiliary power supply by changing the traction motors ventilators.

The advantages of the chopper using on KT4D tram:

• - energy saving of about 40%,
• - minim expenses to introduce chopper in the circuit diagram,
• - accelerator elimination as well as the elimination of a great part from the braking/starting resistors,
• - using of the existing traction motors as well as their protection by chopper,
• - improvement of transport ambience by avoiding the braking / starting jerks,
• - increasing of contactors life by controlling the braking current,
• - re-using of subassemblies as spare parts (contractors, resistors, etc).

The static converter assures the storage batteries charging as well as the whole DC consumption and it offers a 3x380 VAC threephase system that allows the supply of the traction motors ventilators.