The phenomenon of bearing currents is known for a long period. Especially those which are caused by magnetic asymmetries have been investigated since the beginning of the 20th century. Nowadays new kinds of bearing currents can be observed in inverter fed induction drives. Investigations done on these effects show that the switched operational mode – especially of voltage source inverters – causes a high frequency common mode voltage (CMV). This voltage supplies the common mode circuit of an electrical machine in which the bearings are a part of. Therefore, to reduce the occurrence of bearing currents it is necessary to avoid or - at least - to minimise the common mode voltage in drive applications fed by voltage source inverters. A novel principle for such a purpose is the space vector based modulation with sequentially positioned pulses (SPP). With this modulation it is possible to reduce both the number of edges within the CMV and its amplitude to a great extent without influencing the modulation index. The present paper summarises the ideas which stand behind the principle of SPP and gives an overview over the major dependences from characteristics of the drive system. Moreover, the functionality and the compatibility to standard inverter fed drives is shown by means of simulations and measurements.
| Filename: | EPE Journal - 14-4 - 4 - Zitzelsberger |
| Filesize: | 151.5 KB |
