The Motor Load part represents the losses due to the load, it consists of an arbitrary voltage source that transforms the current from the mechanical part to speed in RPM. The losses due to the load are inversely proportional to the resistance between the voltage source and ground. The fan used in this example is permanently connected to the motor, so the losses due to the fan are already accounted for in the mechanical part. In normal operation, there is infinite resistance between the voltage source and ground (open circuit), representing no load.
To simulate a fan failure, such as something getting stuck in the fan, the model also has a switch that will short the voltage source to ground. This switch is triggered by a pulse coming from the Fan_Failure_Trigger voltage source.
