How to control two frequency converters with a 4–20mA signal
Thread Content
Dear sea friends: Many of the pumps in our workshop are controlled by frequency conversion. The pumps operate in one active and one standby configuration, with one frequency converter controlling the two pumps. Some frequency converters allow manual adjustment of the frequency, while others are regulated by a 4–20mA signal from a PID control instrument. It has been found in production that, in some very important situations, it is safer and more reliable to use one frequency converter to control one pump. My question is, if two frequency converters are used to control two pumps, these frequency converters are not used simultaneously; one pump and its corresponding frequency converter serve as spares. I think it’s better to use the 4–20mA signal from the PID controller to control these two frequency converters. May I ask how to implement this function? ?
Isn’t it enough to use a changeover switch to solve the problem?
Do not skimp on PID control instruments; it will lead to problems later
Is it possible to save costs by using one PID table to control two frequency converters? Since the province is being saved, the controller can be omitted as well; simply use the built-in PID function of the inverter.
Use a one-in-two-out signal isolator.
If there is a DCS, it’s very simple: make a choice on the DCS, select A to use it, or choose B otherwise. In the program, this binary choice signal is inserted. There is no DCS to act as a switch
It seems quite simple; it’s probably the simplest and most effective method!
A signal isolator with one input and two outputs will definitely work! Do you have such materials there?
:The PID function built into the L inverter cannot be used! The frequency converter is installed inside the distribution panel, and it must not be operated by employees casually. Employees are not allowed to enter the distribution room. The operators can only control the items on the instrument panel.
These two frequency converters are controlled using the 4–20mA signal from the PID control instrument; an analog input/output safety isolation device with one input and two outputs (such as GS8535-EX) is installed on this 4–20mA signal – the input being the 4–20mA signal itself； Two outputs with 4~20mA signals. Use this to control these two frequency converters.
Actually, all you need to do is ensure that both frequency converters are powered on, and then connect the 4-20mA signal input points of the frequency converters in series; the start and stop of the frequency converters can be controlled separately.