COMMUTATION OF DC MACHINES WITHOUT COMMUTATION POLES BY MEANS OF EXTERNAL ELECTRONIC DEVICES

In DC machines commutation may be performed inside the rotor by means of commutating poles. This is the classical way which gives good perfo rmances in normal working but presents some limits for unsteady runnin g conditions. This paper deals with a special commutation process, fro m the outside of rotor, which is achieved without commutating poles th rough an electronic circuit connected with the commutator. The device is easily drived from the actual rotor position and is able to adjust commutation to miscellaneous conditions. Besides driving versatility, such process allows the suppression of commutating poles whose size is about 20 per cent of main poles. The possible weight reduction is att ractive. The paper presents theory and experiment on a classical DC ma chine with a lightly altered commutator at a level of some kW.