| 摘要 |
PURPOSE:To prevent a brush spark by exciting an auxiliary interpole coil so that transformer voltage induced in an armature coil being rectified by the change of main magnetic flux is denied by speed electromotive force by interpole magnetic flux. CONSTITUTION:The change of main magnetic flux 1 generated by a main pole coil 2 is detected as voltage by a search coil 10, and the change is inputted to a gate circuit 11. The gate circuit 11 controls a control DC power supply 9 so that currents flow through the auxiliary interpole coil 8 in proportion to the output voltage of the search coil 10. Accordingly, even when field control by a field power supply S is exectued suddenly, speed electromotive force proportional to the changing rate of main magnetic flux is generated in the armature coil, and the speed electromotive force densies transformer voltage generating the brush spark, thus previously preventing the bush spark. |
