[Objective] The air-gap magnetic field of permanent magnet generators is non-adjustable

resulting in a limited output voltage regulation range. To achieve an adjustable air-gap magnetic field

this paper studies a hybrid excitation DC generator with a tangential flux-concentrating parallel structure. [Methods] A Maxwell 2D and Simplorer field-circuit coupling model was built. The no-load characteristics and no-load air-gap flux density were simulated by finite element method. The parameter selection of related components in the filter circuit was discussed. The external characteristics were calculated

and the air-gap flux density and adjustment characteristics under armature reaction were analyzed. [Results] The simulation results showed that

under a constant external characteristic load

when the excitation current increased from -12 A to 0 A

the terminal voltage rose by 3.02 V. Further increasing the excitation current from 0 A to 12 A resulted in a terminal voltage increase of 24.66 V. Under armature reaction conditions

the amplitudes of the fundamental wave

5P and 7P harmonics components of the air-gap flux density decreased by 0.05 T

0.02 T

and 0.01 T

respectively

while the amplitudes of the 3P and 9P harmonics increased by 0.09 T and 0.03 T

respectively. The air-gap flux density curve exhibited a trend where one half was strengthened while the other half was weakened. [Conclusion] The no-load characteristics indicate that applying positive excitation to the generator is more effective than negative excitation

making it suitable for low-speed and high-torque applications. The output voltage increases with higher rotational speeds. The external characteristic curve shows that

under negative excitation current

the variation in the generator's phase voltage root mean square value is relatively small

whereas under positive excitation current

the variation is significantly larger. In the adjustment characteristics

to maintain a constant generator terminal voltage

the excitation current must be increased as the load current increases.