How to choose valve electric device

Valve electric device is a device which can complete the valve program control, automatic control and remote control. Its movement process can be controlled by the stroke, torque or axial thrust. The operating characteristics and utilization rate of valve electric device depend on the type of valve, the operation specification of device and the position of valve on pipeline or device.

 

herefore, the correct selection of valve electric device is very important to prevent overload phenomenon (the operating torque is higher than the control torque).

 

Valve electric device has its special requirements, that is, it is necessary to be able to limit torque or axial force. The coupling with bound torque is selected for the electric device of general valve. When the electric device specification is determined, its control torque is also determined. Generally, the motor will not be overloaded if it is operated within the predetermined time.

 

Overload may occur if:

One is that the power supply voltage is low and the required torque is not obtained, which makes the motor roll intermittently;

The other is to adjust the torque binding arrangement wrongly to make it larger than the intermittent torque, resulting in continuous excessive torque and intermittent rolling of the motor;

Third, the intermittent use of heat savings, exceeding the allowable temperature increment of the motor;

Fourth, for some reason, the torque is too large because of the shortcomings of the torque binding arrangement circuit;

Fifth, the use of high ambient temperature, relatively make the motor thermal capacity decreased.

In the past, the methods of motor protection are fuse, over-current relay, thermal relay, thermostat, etc., but these methods have their own advantages and disadvantages. There is no reliable protection method for the electric device, which is a load changing device.

 

Therefore, it is necessary to use a variety of combination methods, summed up in two ways: one is to judge the increase or decrease of the motor input current; the other is to judge the heating condition of the motor itself. Either of these two methods should consider the time margin given by the thermal capacity of the motor.