Figure is the circuit diagram of a speed-control system in which the dc motor voltage va is supplied by a generator driven by an engine. This system has been used on locomotives whose diesel engine operates most efficiently at one speed. The efficiency of the electric motor is not as sensitive to speed and thus can be used to drive the locomotive at various speeds. The motor voltage va is varied by changing the generator input voltage vf. The voltage va is related to the generator field current if by va = Kfif.
Derive the system model relating the output speed ω to the voltage vf, and obtain the transfer function Ω(s)/ Vf(s).

Transcribed Image Text:

Generator Motor Ru