Piotr Chudzik

State Transitions in Vector Controlled AC Tram Drive

The paper deals with the control strategy for the prototype AC tram drive designed for modernization of existing trams in Poland. The basis of the drive are vector-controlled induction motors sourced from voltage inverters. Motor shaft speed sensing enables torque and rotor flux indirect control in stator-current oriented co-ordinates system. In the paper the block scheme of such a control is given and distinct work-states of the drive during the tram driving by motorman are described. Traction properties of the drive were checked during street tests of the tram. During tests the behavior of the drive in dynamic states while accelerating and electromagnetic braking of the tram was especially observed. Results of these observations at different tram drive operation conditions in a form of torque and speed transients were enclosed.

Control of rotor flux in AC tram drive during sudden braking operation

The paper focuses on the behavior of the rotor flux indirect control system for an inverter fed AC tram drive. The control strategy used in this drive is based on the original state stimulator concept and has been applied in several modernized trams and in a trolley-bus in Poland. In these vehicles some oscillations of the modulus of the rotor flux vector during sudden braking operation were observed. The phenomenon of oscillations was tested in laboratory stand with adequate physical model of real tram drive as well as in a computer simulation model. These research allowed to explain the nature of the oscillations and to find some way to improve the control quality.