LCL filters for recuperative frequency converter systems

Moreover, in combination with a recuperative frequency converter system, the LCL filters can significantly reduce the line-side harmonics to less than 5%. Thanks to the integration of the choke in the LCL filter, the recuperative unit can also be operated as a boost converter for higher DC link voltages.

The LCL filters are designed for rated currents of 16, 66, 200 and 400A at a rated voltage of 520V. The two smaller versions (16 and 66A) are accommodated on a mounting plate for ease of use. The larger versions (200 and 400A) consist of two units: a separate storage choke and a mounting plate with power choke and capacitor bank. The filters are designed for clock frequencies of 7-16kHz for the feedback module and 4-16kHz for the motor-side frequency converter module.

Additionally, they are designed for a maximum motor lead length of 150m or 6 axles and a maximum motor frequency of 100Hz. Damping resistors integrated in the module prevent the development of natural oscillations. The filters are designed as open modules with convection cooling to protection class IP 00 (corresponding to IEC 60529 2001). Protective covers are available upon request under ordering code B84143Q*R405. Protection class IP 20 is consequently reached.

Compared with single power chokes, LCL filters are characterised by a significantly improved reduction of harmonics as well as of the voltage and current distortions with respect to the power line. Moreover, the LCL filters have a lower voltage drop and are more compact and lightweight than equivalent power chokes. The filters can be adapted to customer requirements if desired.