python01

Measuring motor current without VFD?

8 posts in this topic

I have project where I need to measure motor current but I do not need to control the speed of the motor since it would always be running at full speed. Do I still need to use VFD to get feedback or is there cheaper way to measure the current?

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Inline Amp meter that mounts to the front of the panel?

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If you just want to measure the current in the PLC, and you already have thermal overloads, you can use a product like this: (http://www.redlion.net/sensors/current-sensors) Look in the "Current Transducers" area Another option is to use a Smart Overload Relay such as the E3 Plus (http://ab.rockwellautomation.com/Circuit-and-Load-Protection/LV-Motor-Protectors/E3-Plus-Overload-Relays). You can get the current feedback using communications (DeviceNet, although you can get Ethernet/IP with an adapter. Allen Bradley promises us that an ethernet model is coming out) Hope this helps.

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I must be getting old. I recall when measuring motor current was standard and the questions were; can I and how do I measure this if I have a VFD. Edited by RussB
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I need to feed the measurement to PLC so the E3 Plus from Allen Bradley might be the best option. Another question would be how do I measure current for device powered by 12Vdc?

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I've never done this before, but after searching "DC Current Transducer" I found this: http://www.ce-transducer.com/Current_transducer.asp In particular on that page there is this: http://www.ce-transducer.com/CE-Az11-1.asp It just might fit the bill.

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These work reasonably well and aren't terribly expensive. http://www.automationdirect.com/adc/Search/Search?searchquery=CURRENT%20TRANSDUCERS&cmd=Search&fctype=adc.falcon.search.SearchFormCtrl&TxnNumber=-1 Edited by Mendon Systems

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