Operating torque: torque operation is to select the most important parameters of valve actuators, electric actuator output torque maximum torque valve operation should be 1.2 ~ 1.5 times. Operating Thrust: electric valve actuators of the host structure, there are two: one is not configured thrust plate, the direct output torque; the other is the thrust plate configuration, the output torque of the valve stem nut through the thrust plate is converted to output thrust. Output shaft revolutions: electric valve actuators output shaft revolutions and the number of nominal diameter valve stem pitch, the first few threads, according to M = H / ZS calculated (M is the electric equipment should meet The total number of revolutions, H is the valve opening height, S is the stem transmission thread pitch, Z is the number of stem thread first). Stem diameter: the next shot on the multi-turn type valves, electrical equipment if the maximum allowed by the stem diameter can not be dispensed through the valve stem, the valve can not be assembled into electric. Therefore, the electric device inside diameter of the hollow output shaft must be greater than the next shot of the valve stem diameter. On the part of the rotary valve and rotary valve valve rod in the dark, although not considered by the stem diameter, but should also take full account of the matching stem diameter and keyway sizes, so that after assembly to work . Output speed: If the valve opening and closing speed too fast, easy to produce water hammer phenomenon. Therefore, according to the different conditions of use, choose the appropriate opening and closing speed. Electric valve actuators have special requirements that must be able to limit the torque or axial force. Usually limit the use of electric valve actuators torque coupling. When the electric device specifications determined, the control torque is also determined. Generally operate within a predetermined time, the motor will not overload. However, if the following conditions may lead to overload: First, the supply voltage is low, not the required torque, the motor stops rotating; the second is wrong it is set torque limit institutions to stop the torque is greater than , resulting in continuous excessive torque, the motor stops rotating; Third, intermittent use, savings generated by the heat, more than the allowable temperature rise of the motor; Fourth, institutions for some reason the torque limit circuit fault, the torque is too large; Fifth, the ambient temperature is too high, the relative decline in the motor thermal capacity. Past the motor protection is to use fuse, overcurrent relays, thermal relays, thermostats, etc., but these approaches have advantages and disadvantages. This variable load on the electric equipment installation, absolutely reliable protection method is not. Therefore, we must take a variety of combinations, summed up in two ways: First, changes in the motor input current to judge; second heat of the motor itself to judge. These two methods, regardless of the kind must take into account the motor thermal capacity margin is usually given time, the basic overload protection methods are: continuous operation of the motor jog operation or overload protection, the use of a thermostat; of Stall protection, thermal relay; of a short circuit, the use of fuses or overcurrent relays.