| Abstract |
Electrical machines with permanent-magnet excitation are increasingly gaining in importance because of the growing use of high-energy permanent magnets. Their advantages are found particularly in the possibility of more compact and lighter designs and of dispensing with exciter power. On the other hand, the rigid excitation is a drawback in cases where constant-power operation is required over a wide speed range (weakening of field). Conventional rotary-field machines with permanent-magnet excitation are only conditionally suitable for field-weakening operation, as the current load of the converter is not sufficiently reduced in the process. However, a rearrangement of the magnetic structure of the machine on the transverse-flux principle offers more favorable conditions for field weakening. The following article attempts to show how large speed ranges may be covered at minimum current requirements by optimizing the characteristic of the terminal voltage of the transverse-flux machine (TFM for short). Optimization occurs analytically by application of the maximum principle according to Pontryagin. |
