Control And Research Of Isolation Switch Operating Mechanism

Known as one of the most common power system, isolation switch can be applied to isolate voltage and divide low current. However, some problems may arise when operating the Isolation switch, such as static and dynamic contact reject to divide-shut, unresponsive and not divide-shut brake in the accurate position. In order to solve the divide-shut problem mentioned above, this thesis build a motor control model, and analysis the dynamic characteristics of the resulting curve. The model is built up by controlling the speed of motor shaft side, the four-bar linkage can be driven to make the dynamic contact divide-shut precisely.Firstly, establish the mathematical model by analyzing the operating mechanism of the drive motor, transmission, and load characteristics theoretically. For the drive motor,under the principle of coordinate transformation and vector control, which will enable the asynchronous machine equivalent to DC motor thus control the speed of the motor. For the transmission mechanism, which is regarded as an input- output model, the angular displacement of the motor shaft side of the transmission mechanism considered as its inputs, while the linear displacement of the contact side considered as its corresponding output. Thus turn the 84 mm linear displacement of the contact side into the 64° angular displacement of shaft side. For load characteristics, respectively calculate the gravity of the opening mechanism stage, which is 90 N, friction and the spring preload, which is1600 N, and spring rebound force,which is 30N/cm, of the ultra-way stage, in order to establish the load curve.Then establish the field-circuit-movement coupling model, combining the armature circuit current, magnetic field strength and the rotor motion equations to create differential equations, solving the motor angular displacement,velocity versus time curve to be as the given curve. Based on the use of rotor field oriented control method and pulse width modulation inverter technology the models can be built in Simulink to control motor speed in closed-loop underthe constant load to track the speed curve which is given above. And analyze the motor current, voltage, electromagnetic torque and speed in the process.The curve obtained is accordance with the characteristics of asynchronous motors, for the most time of the process the motor speed can be well tracked,and finally to improve the braking effect by adjusting the load characteristics.Finally, add the load characteristics to the motor control model, by changing the load characteristics of the spring preload and spring rate parameters to improve the braking effect of the motor. Experiments show that with the increase of the stiffness parameters and pre-pressure parameters, the braking acceleration is also increasing, and braking effect is significantly improving. In order to achieve precise 64° angular displacement, through the simulation the best parameters of the spring preload and spring stiffness can be found is 2400 N and 50N/cm. Put the dynamic braking of motor brake theory into the control model, to improve the braking performance. The best value of time to add it in can be found is 0.055 s and the best value of braking resistor is4Ω.In order to avoid the motor into the dead zone, the braking resistor should be controlled above 4Ω.