Modeling of a traditional aircraft generator and its sub-systems

The modeling of a three-stage Integrated Drive Generator(IDG) is presented along with a unique control design for an aircraft application. Based on the overall system ratings of 40 KVA, 115VAC and 400Hz, appropriate design parameters have been estimated for each of the basic components of the three-stage brushless excitation system, namely the pilot exciter, main exciter, and main generator. In addition to conventional PI voltage and current regulators to maintain the rated output behavior under load variations, anew type of current limiter is proposed as a protection mechanism for practical operation under a symmetrical fault. Through simulation studies, it is shown that, while a traditional PI current controller is effective in limiting the steady-state short circuit current to its rated value (350A),introducing a special type of thermistor (NTC) in series with the fault-creating resistors is much more efficient in limiting the transient inrush current induced just at the time of fault. This modeling methodology can be used for transient and steady-state performance analysis under nominal and symmetrical fault conditions.