Brushless Induction Excited Synchronous Generator With Induction Machine Operating in Plugging Mode

This paper describes a new brushless and magnet-less synchronous generator where an induction machine (IM) is embedded in a synchronous machine (SM) to provide the excitation. Hence, this machine is named as brushless induction excited synchronous generator (BINSYG). To avoid the magnetic interaction between both IM and SM, they are configured for different number of pole pairs. A rotating uncontrolled rectifier (mounted on the shaft) is proposed to be used to rectify the rotor voltage of the IM to provide the excitation to the SM. Thus, by controlling the IM from stator side, field current of the SM can be controlled smoothly. As an example, in this work, SM and IM are configured for two pole and six pole, respectively. Practical winding-design-challenges and mutual interaction between IM and SM fields are analyzed briefly for 2/6 (SM poles/IM poles) pole BINSYG. Extensive finite element simulations of the proposed machine have been conducted using Maxwell-2D and these simulated results are obeying the theoretical analysis. A 3 kVA laboratory prototype of 2/6 pole BINSYG has been developed to evaluate the performance when IM is operated in the plugging mode for definite advantages. While a brushless configuration is proposed, brushes and slip-rings are used for the experimental machine, such that, rotor side windings of SM and IM can be accessed for the better understanding of the performance. Experimental results from this prototype confirm the theoretical and finite element method predictions.