Current (A) Torque (N ⋅ m) 30 20 10 0 -10 -20 -30 0 0.5 1 1.5 Time (s) (a) 2 2.5 3 0 0.5 1 1.5 Time (s) (b) 2 2.5 3 0 0.5 1 1.5 Time (s) (c) 2 2.5 3 0 0.5 1 1.5 Time (s) (d) 2 2.5 3 0 0.5 1 1.5 Time (s) 2 2.5 3 30 20 10 0 -10 -20 Speed (r/min) 600 400 200 0 -200 Torque (N ⋅ m) 20 10 0 -10 -20 Torque (N ⋅ m) 20 10 0 -10 -20 (e) Figure 7. The speed ramp and load disturbance torque responses of the ac motor drive: the (a) motor current on the engine emulator, (b) motor torque on the engine emulator, (c) rotor speed, (d) mechanical torque transmitted by the shaft, and (e) motor torque on the generator emulator. speed-torque characteristic of the turbine engine model. Figure 5 shows the closed-loop simulation results of using two different speeds, and the two curves enable tracking of the reference behavior of the gas turbine model with a tracking error below 1%. The next step is to create a real-time observer for the gas turbine model such that a practical hardware implementation can be realized. This work will be discussed 30 I E E E E l e c t r i f i c ati o n M agaz ine / december 2014 in the section "Implementation of Fan Map Observer into Motor-Fan Drive." Propulsive Fan System model and motor-based emulator The goal of this section is to develop a method by which the fourth motor drive system, emulating the last