Hi
I'm planning to build a sensor that measures my 3 pase load, a well pump.
Read data and send to receiving system (LoRa or WiFi).
The pump is connected to a 16 Amp fuse AC 230 V, max load <7 A at 230 AC V
I have looked into Winson HALL current sensor WSC1800 with a sensitivity of 60mA/A
Can you tell me if this is a decent sensor for my needs?
Or maybe point me in another direction.
Data sheet: https://www.winson.com.tw/uploads/images/WCS1800.pdf
Thanks up front!
It looks good as far as I can see.
consider using SCT-013 current clamps which is none-invesive
Might be relevant to remember that motors draw large amounts of current at startup ( 4 to 6 times full load) so perhaps give some thought to introducing a way to disable the module during that period.
Also worth mentioning that analog measurements can hunt all over the place due to noise and other factors so take several readings and average the result.
Non invasive current clamps would be the best choice for amateur.
In addition, your pump may need to get a whole big slug of water moving before the motor gets up to speed and the current drops to the normal running speed. You did not tell us about the starting load on the motor. MY well pump has over 400 feet X 1 1/2 inch column of water to move.
It worth remembering that each phase will draw the same current .. so if you are just monitoring , you could just measure 1 phase.
A fuse (3?) may not offer enough protection and 16A might not be correct either , you need an overload trip on the contactor too to protect the pump against extended periods of overload
If you do an analogRead() to measure the current, then that just measures an instantaneous value of the current.
Depending upon whereabouts in the mains cycle that sample is taken the result can be anywhere between the negative peak of the waveform to the positive peak of the waveform. - It could even be zero.
You need to take multiple readings throughout at least one whole mains cycle, and then do some mathematics to find the rms current.
@Railroader @horace @hammy @Paul_KD7HB @bluejets
Thanks for info and tip.
My well pump is running on a 16A fuse, 3 phase. I have an motor overload fuse also, its dialed in on 6 A. I also think that the pump has a slow start system.
Pump has been running for 5 years so all is working.
Lifting height is from 90 m to 20, depends on how much water is in my drilled hole.
My main idea is to get a grip for how much kWh the pump uses over the year.
Maybe I need to sample 24/7, calculate by interval (i.e. 10 min), and send the calculated value by interval to my dashboard.
Example:
This is new to me, logical for a pump, but anyway new. So to simplify my circuit for a pump, it will be enough to measure a single phase (ie. only one sensor on one of the cables)?
M
if all you require is power why not purchase a 3 phase power meter
No, you need to measure all three currents and all three voltages in order to obtain the true power and the VA so you can compute the power factor
It’s a fair cop …You can get power from one phase , but bit more complicated than I initially thought and needs two voltages to be measured .
Here
Buying a power meter is a good way forward and makes a neat safe installation. 3ph voltages are high and it really needs a professional to make connections to it and have safe circuitry .
Thanks for info @jim-p . Can you elaborate for me, so I may learn something?
The load is a single pump, no other devices connected that make changes in load balance compared to a fuse box.
When I measure amps with a clamp meter, each phase has measured value of 4.7 Amps, so it seems logical that I can get a result amp= sqr^3 * 4.7 = 1,7*4.7 = 8.14 A.
Thanks up front!
M
I have ordered 6 pcs :-), and 6 pcs WSC1800, so I have something to play with.
Because I like to make things 
and also present values on my Home assistant dashboard.
I think if you connect the 3 sensors in parallel as you show them the output voltage will be zero? It isn't entirely clear from the datasheet but it looks like they give an alternating voltage when sensing an alternating current.
Oops! No, those are the power connections!
also have a look at 4-Channel-Mains-Current-Sensor-ESP8266
I use it to measure the 3 phase current to the house
I sample the current over a few seconds to calculate the RMS value and hence power
with a 100amp clamps the value is within a couple of percent of the current displayed by a commercial current clamp meter
It's hard to explain without pictures and diagrams.
If you google "measure 3 phase power" you will see explanations about power, 2 and 3 wattmeters and power factor.
Thanks for info!
In, Norway, where I live we don't have a common cable (same as in Albania), only 3 wires into mains, 3 phases, ground is connected to ground/earth for each plot/house.
The PCB they show in GitHub - Mottramlabs/4-Channel-Mains-Current-Sensor-ESP8266: 4 Channel Mains Power Sensor
Is all diagrams open source, I could not find it?
M
Yes, that is all you need. Measure two currents and two voltages.
