The expander is usually braked by the motor. Its principle is to control the speed of the expander by using the braking torque generated by the generator braking state of the motor. Once the braking motor fails, the speed of the expander will be out of control and it will be over speed. At this time, it is necessary to automatically open the protection and control system. The principle is that the speed measuring motor sends out the overspeed signal to power off the three-way solenoid valve. The three-way solenoid valve directly controls the pneumatic butterfly valve at the inlet of the expander, so that the butterfly valve can be quickly closed and the air inlet is cut off. At the same time, the rotation of the valve rod touches the stop and the limit switch to cut off the power supply of the expander motor, so as to realize the safe shutdown.
