Ich habe in 4 Gebäuden je 1-2 VM-3P75CT installiert, aber der Leistungsfaktor stimmt bei keinem einzigen. Da werden Werte zwischen -1 bis 1 angezeigt, ich erwarte hier einen Wert von ca. 0.85 - 1. Sogar im Handbuch zu dem VM-3P75CT ist auf Seite 8 ist die App abgebildet wo der Leistungsfaktor 0.359 beträgt!
Die Messumwandler sind alle korrekt angeschlossen und die Zählung gegenüber dem Netzbetreiberzähler stimmt ±2% überein, also sollte alles fröhlich sein in der Installation.
Hi @DStuder, I think you are referring to the negative value (-0.974) of the power factor correct? This is the result of the power factor convention used in the VM-3P75CT.
The negative power factor in combination with the negative total power tells us that the system is slightly inductive. If the installation isn’t actually exporting power to the grid, then the CTs are flipped (for the grid role: negative power is exporting, positive power is importing).
Ah, okay, that explains a lot. Yes, I mean the power factor. What exactly does a power factor of 0.587 mean? I’m not quite getting it at the moment.
I think a power factor of 1.0 indicates a resistive load when drawing power from the mains, right? But what about a power factor of 0.2 or even 0.6? Could you explain how to interpret the image below?
Hi @DStuder, the amplitude of PF is simply the real power divided by the apparent power (W/VA). Apparent power is the RMS voltage of the system multiplied by the RMS current flow. Real power will be lower than apparent power in case of a phase-shift between the voltage and current waveforms or in case of non-linear loads. For more info see this section of the Wiring Unlimited book.
A power factor of 0.587 means that only 58.7% of apparent power is actually doing real work.
In your case, L1 barely uses any real power, but you do have 235.6V*0.5A ≈ 120VA of apparent power, and so PF = 11W / 120VA ≈ 0.095.
With P.F. best keep in mind that, when the power that is measured by the CT is very low (<0,5 Ampere) and grid import/export is about zero, the calculation based on these minor ac-amplitudes is very difficult, also for electronic modules. So often the readings at very low power, the P.F. is to be ignored imho!
Hello Luc and phaseshifter, thank you for your answers. I understand the power factor calculation because I studied electrical engineering. For this reason, I find it hard to believe that the PF could be so poor.
Here is an example where the house only has the base load. In the second screenshot, a larger heat pump for two buildings is also running.
But I can bring the large FLUKE network analyzer from my company with me when I get the chance so that we can record it accurately. You never know…
I think you will find the Fluke not giving you any better outcome over the Victron.
These days the usual household is strewn with switch-mode power supplies, LED-bulbs, smoke alarms (look up the datasheet for a 230V smoke alarm… 5VA and 30W) end what not. All these supplies under 30W are not required to have active power factor correction and with the universal law of economics; 99% of devies will not have PFC.
As an example, our house during the evening hours has an average PF of 0.6. Admitted, that is with a total load of around 150W to 400W, so there will be a lot of measurement noise (EM540 as a grid meter).
Unfortunately, I have never paid attention to the power factor with such small loads, but with Victron I am seeing it live for the first time. I would be surprised if they really are that bad with small loads. But yes, the base load consists of power supplies and a few heating pumps. You never stop learning; I have never looked into this in a private household.
I would also like to thank you guys for your help.
