OpenEVSE DIY Tethered 3-phase

jo_llo · 2020-03-23T19:34:18.466Z

As you can see on the screen shots the calculated power is 230V (V line-neutral) × I = power in monophasic system and I’ve a triphasic.
In the calculation formula it’s missing cos(FI). Do you know the cos (FI) value for this charger ?

Can you please implemented the following formula to the 3 phasic system FW ?
Power = 400V x I x sqrt(3) x cos (FI)

Captura de Pantalla 2020-03-22 a les 18.34.221250×580 42.5 KB

glyn.hudson · 2020-03-24T00:00:31.893Z

This is how threephase energy is calculated:

github.com

lincomatic/open_evse/blob/development/firmware/open_evse/EnergyMeter.cpp#L65

    
      
            else clrEvConnected();
          }
          
          
void EnergyMeter::calcUsage()
          {
            unsigned long curms = millis();
            unsigned long dms = curms - m_lastUpdateMs;
            if (dms > KWH_CALC_INTERVAL_MS) {
                uint32_t mv = g_EvseController.GetVoltage();
                uint32_t ma = g_EvseController.GetChargingCurrent();
                /*
                 * The straightforward formula to compute 'milliwatt-seconds' would be:
                 *     mws = (mv/1000) * (ma/1000) * dms;
                 *
                 * However, this has some serious drawbacks, namely, truncating values
                 * when using integer math. This can introduce a lot of error!
                 *     5900 milliamps -> 5.9 amps (float) -> 5 amps (integer)
                 *     0.9 amps difference / 5.9 amps -> 15.2% error
                 *
                 * The crazy equation below helps ensure our intermediate results always
                 * fit in a 32-bit unsigned integer, but retain as much precision as

- P(3ph) = V(LN) * I * 3
- V(VL) = 230V (line to neutral voltage)
- V(LL) = V(LN) * √3 = 230 * 1.75 = 400V

github.com/lincomatic/open_evse

Three-phase energy calculation option

lincomatic:development ← openenergymonitor:3-phase

opened 12:29AM - 13 Mar 18 UTC

glynhudson

+51 -44

- Added option to calculate 3-phase energy ~~(multiple current by the square roo…t of 3).~~. - Disabled by default My notes on three-phase calculation: ``` - P(3ph) = V(LN) * I * 3 - V(VL) = 230V (line to neutral voltage) - V(LL) = V(LN) * √3 = 230 * 1.75 = 400V ```

jo_llo · 2020-03-24T08:13:47.351Z

Hi Glyn
Thanks for your patience.
Please take a look of my screen shot
Intensity = 12.76 A and Power = 2935 W
That means Voltage = 2935 / 12,76 = 230 V, and not 230V x 3
Then your software to calculate the energy is correct but there is a bug:
THREEPHASE is not active in the firmware and it continue to calculate as a Monophasic system.
Kind regards
Jordi

jo_llo · 2020-03-24T08:15:39.495Z

Glyn I have a second question:
In the formula we miss COS (FI)
Power = Voltage LN x Intensity x 3 x COS (FI)
do you know the value of COS (FI) in this charger?

jo_llo · 2020-03-24T08:34:01.246Z

probably TREEPHASE it’s not defined at open_evse.h

KR

glyn.hudson · 2020-03-24T14:50:07.120Z

Please try again with the FW attached, I have explicitly defined THREEPHASE

openevse-3ph.hex (85.8 KB)

If this doesn’t work you could try building the FW yourself. Three-phase calculation works for the EmonEVSE.

jo_llo · 2020-04-04T17:13:45.703Z

Hi Glyn
Thanks for your patience
Now it works
Thanks a lot
Jordi

glyn.hudson · 2020-04-07T12:21:45.442Z

Fantastic! Very sorry, for all the hassle. The mistake must have been at my end.

Maciej_Blaz · 2020-12-28T07:10:52.135Z

Hi,

I know that this is an old thread, but have a question about 3-phase installation and setting the THREEPHASE constant. Is it possible to change it on the fly? For example have some toggle in the web ui to be able to switch it to either 1-phase or 3-phase? Basically I have 2 cars (one has single phase charger and the other has 3 phase charger) and I would like to be able to switch the param on and off based on which car is currently charging. Ideal solution would be to add one more current meter (on L2 or L3) so that the software knows automatically if I’m charging 1 or 3 phase car.

Thanks in advance.

gadgetbazza · 2021-07-12T13:43:11.309Z

I’ve just had a 3 phase EmonEVSE installed and despite the firmware being reported as 7.1.3.3P, I too see only single phase energy calculations both in the UI and the MQTT feed to my EmonCMS.

I’m also unsure therefore if the PV divert is going to be observed correctly on the grounds that the value I’m returning about grid import/export is for all three phases, not just one.

I see the reference in this thread to the constant THREEPHASE being defined, but no detail on how to set this? I would also expect that to have been set correctly in this firmware?

glyn.hudson · 2021-07-22T23:46:17.919Z

The OpenEVSE UI displays real-time charging current, which is the same for both single and three-phase e.g 32A 1P = 7kW / 32A 3P = 22kW. However, the kWh/wh reported on the OpenEVSE UI and Emoncms will show the correct energy calculation for 3P.

Solar PV divert is based on current, therefore should work the same for both single and three-phase.

gadgetbazza · 2021-07-23T00:00:26.024Z

Hi Glyn,

thanks for replying.

I get the 32A bit. But on the emonCMS, there is only one energy calculation and it only shows the power for a single phase on my 3 phase unit. Please see attached screenshot showing the consumption at circa 3.7kW, the unit is actually charging at 11kW. This is the reasoning for my query.

I’ve had to add the energy feed to each of my 3 phase monitors to get my total usage correct.

Screenshot 2021-07-23 at 00.55.251710×1612 355 KB

glyn.hudson · 2021-07-23T14:41:13.908Z

gadgetbazza:

But on the emonCMS, there is only one energy calculation and it only shows the power for a single phase on my 3 phase unit. Please see attached screenshot showing the consumption at circa 3.7kW, the unit is actually charging at 11kW. This is the reasoning for my query.

Thanks for the screenshot, I can see the issue. The charging power shown on Emoncms is calculated in Emoncms input processing, the amp current Input is multiplied by 230V to display the power, this should be multipled by 3x for three-phase.

To change this, open up Emoncms Inputs and click the spanner icon next to openevse ‘amp’ feed:

Emoncms-input-view2504×798 83.1 KB

Then change 230 to 230V x 3 = 690

Emoncms-input-view (1)2444×1223 259 KB

The power will now be displayed correctly. Alternatively, for more accurate power reading, you could multiple by emonPi VRMS feed x3

The ev_energy Feed should be correct for three-phase since this energy is calculated on the openevse.

To make this easier for new users, I’ve added a three-phase device template which will do this automatically, but since you already have your Feeds setup it’s probably easier to adjust manually. Thanks for reporting this issue.

3-evse-sw1440×1056 73.5 KB

Robert.Wall · 2021-07-23T14:44:28.344Z

Are you suggesting “230” (or 3 × 230) to allow for a non-unity power factor - because the UK ‘centre’ voltage is likely to be closer to 240 V ?

glyn.hudson · 2021-07-23T14:47:48.866Z

You’re right, obviously a better option would be to

glyn.hudson:

Alternatively, for more accurate power reading, you could multiple by emonPi VRMS feed x3

Like this:

Screenshot 2021-07-23 15.47.182410×1202 192 KB

dBC · 2021-07-23T23:06:13.270Z

I’m not sure how your supply compares to ours, but I see about a 5V drop when the EV starts sucking 32A. That’s measured at the fuse box so doesn’t include any additional drops in the run to the EVSE (single phase setup).

Screenshot from 2021-07-24 08-49-21930×231 24.5 KB

I also had a chance recently to capture the current signatures of the on-board chargers of a few different EVs at various power levels:

mg_zs_ev850×400 7.13 KB

MG ZS charging at 30A (though 32A was on offer)

mg4_wav23850×400 7.05 KB

MG4 charging at 30A (though 32A was on offer)

erm_a87177_wav23_model3_32A850×400 7.1 KB

Tesla Model 3 charging at 32A

erm_a87177_wav23_model3_5A850×400 7.01 KB

Tesla Model 3 charging at 5A

erm_a87177_wav23_eqc_32A850×400 7.09 KB

EQC 400 charging at 32A

erm_a87177_wav23_eqc_preheat850×400 7.1 KB

EQC 400 not charging, but pre-heating the cabin

xc40_32A850×400 6.73 KB

Volvo XC40 at 32A

xc40_16A850×400 6.48 KB

Volvo XC40 at 16A

xc40_6A850×400 6.61 KB

Volvo XC40 at 6A

Robert.Wall · 2021-07-23T23:29:25.927Z

dBC:

I’m not sure how your supply compares to ours, but I see about a 5V drop when the EV starts sucking 32A.

That’s about 360 - 370 kVA, so that’s about the same as an urban UK domestic supply. I can’t speak for a rural supply, but it could well be significantly lower.

dBC · 2021-07-24T23:06:36.193Z

How did you work that out? Is that some rule-of-thumb for distribution transformers based on the effective impedance?

Robert.Wall · 2021-07-24T23:45:28.804Z

Ohm’s Law. If you say the supply has a source resistance (not impedance), it’s going to drop a voltage depending on the load (again a resistance). You know both, so you can calculate the supply internal resistance (again, not impedance). That determines the prospective fault current, and that’s the maximum (or rather, more than the maximum) power you can get in the fault. It’s not accurate, but it gives a ball-park value.

Your supply fuses will operate long before that current is reached, but that’s where it’s heading.

I think the UK network is designed so that it’s around the 300 kVA mark for most consumers - but I’m really a drives & controls applications person, not a power systems one.

glyn.hudson · 2021-07-29T15:56:22.660Z

dBC:

I also had a chance recently to capture the current signatures of the on-board chargers of a few different EVs at various power levels:

Nice, that’s fascinating. I think it would be worth creating a dedicated thread for these captures. It would be interesting to build up captures for lots more EVs. I would be interested to see how a Leaf and a Zoe compare, I’ve heard a Zoe has poor power factor.

I think the reason for the double spike on the Model 3 is because the model 3 has a 3x 16A chargers (three-phase 11kW) so to achieve 32A single-phase the car connects multiple phases of the onboard charger together.