Dear sir,

Has anybody done an application in which KW i.e power consumed by the machine was displayed on HMI through PLC Interfacing? Which company was making such instrument? In my application, I want to Display power consumed by the machine HOURLY.

Regards,
Ash

 

Ash,

Why interface with the PLC when you can use a power meter that reports KW, etc., directly to your HMI?

Check out this site: http://www.oksatec.com/Powermeters/Powermeters.htm

These meters can be connected on the same network as your PLC.

Good luck,

Zvi

 

First off, power is the rate of energy used, so you would not display power used per any period of time.

If you want to calculate energy used, this is a simple integration problem if you know the power. There are many power meters available that will tell you the power being used in a device.

 

Try OhioSemi.com

They Sell killowatt hour meters.

 

Do you want to display instantaneous power (kW) or Energy (kWh) or average Power ? I guess the latter. Find a kWh transducer that produces pulses (e.g., 1 pulse per 0.001 kWh), count them over one hour period , store the result,
reset the counter, display the result as historical trend or value for last full hour. Same can be done with transducer with serial connectivity (e.g., over MODBUS).

Meir

 

Schneider Automation have an extensive line or power monitoring equipment. It supports Modbus over TCP/IP and has a built-in Ethernet jack.

You can find out your kW, kVA, kVAR, Power Factor and so on.

I am sure, also, that people will make clamp-on ammeters that can be fed back into an analogue input on your PLC. Perhaps someone else on the List knows who.

RA

 

> Dear sir,
>
> Flex-Core company (614)889-6152) sells AC Watt transducers which convert watts into 4-20mA. They come in a wide array of input ranges. You will most likely need a current transformer for your AC current input and possibly a potential transformer for your voltage input (depending on the voltage level). The 4-20mA can be taken into an Analog input on your PLC and scaled to any number you wish. Hope this helps>
Regards,
> Jim

 

You have several options depending on what you want to do. If you want to record energy consumption (KWH) you'll need a power meter like Power Measurement ION, or AB Power Monitor. The interface to your PLC could be a discrete pulse count for example, every 10 KWH send a pulse to your PLC. Many power meters also support several PLC protocols like Modbus, or AB Remote I/O. If you only want to display power (KW) then all you need is a watt transducer, and most like some metering transformers (PT's & CT's).

 

Ohio Semitronics makes some good power monitoring transmitters. The ones with which I'm familiar have a process (4-20) output, so you'd need a PLC in between or an MMI with some built in I/O. You might be able to find a power monitor with a network connection, like Profibus or DeviceNet.

 

I Have done this a few times, we have used a local(South African ) instruments from a company called power contractors to read 4-20ma signals for this purpose, and have also profibus devices, Siprotec and Simeas P from Siemens which can provide this information.

Regards Donald Pittendrigh

 

A minor modification to the collection algorithm would give a more up to date running count for the last hour. Save smaller intervals, say 5 minutes. In your display total, every time you get a new 5 minute interval value, subtract the value you got 1 hour ago and add the new value.

This involves keeping a 12 position table or array, and a pointer into the table. Each new update subtracts the old value, puts the new value in the table, then moves the pointer to the next position (going back to the start of table after 12 moves)

This way the value is (more or less) the consumption within the previous hour, not the burn rate for an hour anywhere from the last hour to two hours ago.

Rufus