Electrical Machines and Drives by Jan A. Melkebeek

Author:Jan A. Melkebeek
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Direct starting of squirrel-cage induction machines on the mains supply may result in two important problems: a limited starting torque for high power ratings (due to low rotor resistances), and a starting current which is too high.

There is no simple standard solution for the relatively low starting torques of high-power machines on a fixed frequency supply. As will be shown in Chap. 15, variable frequency supply offers an excellent solution (also for starting purposes).

For the high starting currents in the traditional fixed frequency supply situation, there are several possible solutions. The ultimate aim of these is to reduce the starting current as much as possible, while limiting the reduction of the starting torque. These standard starting methods include wye-delta, auto-transformer, series-parallel, stator resistance, and inductance starting. The first three methods realise a mains current reduction which is equal to the torque reduction, while for the last two the torque reduction is larger than the mains current reduction (see Table 13.1).Table 13.1Standard starting methods

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