Electric actuators, like pneumatic actuators, are an important part of the control system. It receives 4-20mA or 0-10mA DC current signals from the controller and converts them into corresponding angular displacement or straight stroke displacement to manipulate control mechanisms such as valves and dampers for automatic control.
Electric actuators are available in straight stroke, angular stroke, and multi turn types. The angular stroke electric actuator uses an electric motor as the power component to convert the input DC current signal into the corresponding angular displacement (0-90 degrees). This actuator is suitable for manipulating rotary control valves such as butterfly valves and baffles. The straight stroke actuator receives the input DC current signal and causes the motor to rotate. It is then decelerated by a reducer and converted into a linear displacement output to operate various control valves such as single seat, double seat, three-way, and other linear control mechanisms. The multi turn electric actuator is mainly used to open and close multi turn valves such as gate valves and globe valves. Due to its high motor power, the maximum power is several tens of kilowatts, and it is generally used for local control and remote control. These three types of actuators are all position Servomechanism powered by two-phase AC motors. Their electrical principles are identical, but the reducer is different.
The main performance indicators of the angular stroke electric actuator are: three-terminal isolated input channel, input signal 4-20mA (DC), input resistance 250 ohms; Output torque: 40, 100, 250, 600, 1000N · m; The basic error and variation are less than ± 1.5%; Sensitivity 240 μ A.
The electric actuator mainly consists of a servo amplifier and an actuator, with a series of operators in the middle. The servo amplifier receives the control signal from the controller and compares it with the feedback signal of the electric actuator's output displacement. If there is a deviation, the difference is amplified by power and drives the two-phase servo motor to rotate. Then decelerate through the reducer to drive the output shaft to change the angle. If the difference is positive, the servo motor rotates forward and the output shaft angle increases; If the difference is negative, the servo motor will reverse and the output shaft angle will decrease. When the difference is zero, the servo amplifier outputs a contact signal to stop the motor, and at this time, the output shaft stabilizes at the corner position corresponding to the input signal. This positional feedback structure can achieve a good linear relationship between input current and output displacement.
The electric actuator can not only cooperate with the controller to achieve automatic control, but also switch between automatic control and manual control of the control system through the operator. When the switching switch of the operator is placed in the manual operation position, the power supply of the motor is directly controlled by the forward and reverse operation buttons to achieve forward or reverse rotation of the output shaft of the actuator, and remote manual operation is carried out.
