I need to know when a 3 phase AC submersible pump is turned on, for the sake of logging it to a online database. Thing is, I do not know how tell if it is ON, or OFF. I've given a thought to using a current transformer, specifically the "STC-013-30" one, but it requires to be wrapped around one of the AC wires (live/neutral) but the motor i have has both the wires insulated together forming a single, huge wire. Plus, its 3 phase, and I do now know if the STC can detect 3 phase currents. Can it be done some way? Can I utilise some other tool to tell if the motor is ON?
It's likely that the power to the motor is originating at a panel with breakers. You should be able to confirm that only one breaker set is being used to power the pump motor. At that location, all the wires are separated.
If you do not have the necessary skill to identify the correct wires, consider to consult an electrician. It is advisable to remove power to the panel before you begin to insert your fingers to wrap the sensor wire around the correct lead.
The long and short of it is that you need to measure the current. And there's two basic methods of doing that, and both require access to just one of the wires in the cable.
So you will either have to take a knife to your cable and carefully remove a section of the outer insulation to access the wires within it, or create some kind of adaptor cable that the existing cable plugs into (however that is done on your system) to allow access to the individual wires.
Then it's a case of either:
- Use the magnetic field of one wire to monitor the current (current transformer) or
- Introduce a shunt resistance into the current path and measure the voltage drop across it.
The first option is by far the safest.
Alternatively there may well be some form of commercial three-phase power monitor with an output that you can monitor to achieve what you want with less danger of electrocuting yourself and others in the process.