Modeling and Simulation of Vehicular Power Systems - webfiles its ...

Figure 8-7 Engine and generator power and speed curveFigure 8-7 also shows the speed and torque characteristic of the engine and generator. Ascan be seen, the speed of the engine jumps between 840 rpm and 1600 rpm. When thereis a power demand the engine speed is set to 1600 RPM and the reference torqueaccording to the demanded power and engine constraints is calculated. The jumps in thespeed of the engine and generator are because of the dynamics of the generator –engineset which has been modeled by a first order system considering the inertia of thegenerator-engine set.Figure 8-8 shows the performance of electric traction motor. Once the vehicle acceleratesthe torque of the motor is maximum as the speed reaches the maximum speed. In thecycle the acceleration is zero so the motor power suddenly decreases because it does nothave to overcome the inertia of the vehicle and accelerate the total weight of it. It can alsobe seen that during the deceleration the power is negative which indicates that energy isbeing fed back to the motor to charge the batteries. The traction power and efficiencyincludes the efficiencies of gear box and power electronics.55