:(Doubts regarding the setting of current frequency meters on field operation columns in the chemical industry)~
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This post was last edited by yy678 on 2019-4-3 08:21. I work in design; for fans equipped with variable frequency drives, ammeters and frequency meters are installed on site. There is also a 10K adjustable resistor on the control panel to facilitate operation on-site, though in actual operation it is usually done remotely. But now, after seeing the designs of many variable-frequency fans, I find that in practice they are just like ordinary motors – they have only indicator lights for operation and stop, as well as start and stop buttons. I was wondering, which one is more reasonable. Is there such a standard in the chemical industry? I’m confused~~:(
The DCS has a feedback display; bringing it to the site seems a bit of a waste
I also think remote control is sufficient; air-cooled motors are usually located at the top of the frame, which makes it very inconvenient for operators to access them. Additionally, the purpose of controlling the fan speed using variable frequency is to regulate the cooling temperature, and this should be done through DCS operations. Therefore, remote control is adequate, as on-site installation would result in very low utilization rates
Not only devices with variable frequency, but ordinary pump motors used to be equipped with ammeters as well; nowadays, many designs omit this feature. Personally, I think it’s better to have them paired together, as it facilitates on-site assessment of the equipment’s operating status.
:This is really a matter of personal design habits~~~ If the current frequency is set, the cables need to be run through the instrument tray; probably many people working on this are electrical engineers. So, to avoid complications, this step is omitted? ? ? ?
Most of the frequency conversion data is transmitted from the inverter cabinet to the DCS via interlock cables, including motor current, motor status, and DCS set frequency signals. The ammeters installed on-site must be designed by electrical specialists and routed through electrical cable trays, along with the control cables for the operation panel. Interlock cables are now also primarily designed and provided as part of the electrical design; the instruments are installed by the electrical team, using the DCS I/O diagrams along with the wiring diagrams provided by the panel manufacturer. But I have to complain that in electrical design, the motor numbers are usually indicated on the cables; while the instrumentation diagrams only provide terms like XX compressor or XX production water pump. As those of us who carry out the construction work have to refer to the electrical equipment diagrams to find out what kind of motor or pump it is, and then check the instrumentation diagrams to determine which terminal in that cabinet corresponds to that particular point. Can’t you designers write a bit more detail? Q:Q
These days, inverters generally have a current signal output, that is, a 4–20 MA signal, which can be transmitted through the instrument cable tray. These days, almost all pump units are equipped with protective components such as thermal relays and magnetic contactors; it is generally not necessary for personnel to monitor the operation of the pumps on-site, as the operation signals can be viewed on the DCS screen. Only for slightly more important equipment is it necessary to have centralized monitoring of the current.