Request help with power curve "Hilfe anfordern mit Leistungs

[GoVertical]

Greetings, what is the procedure for creating a power curve for a 3 phase permanent magnet alternator.

I am currently working on a 8 coil per phase PMA.

I know when the PMA is connected to a battery the voltage is set to the voltage of the battery.

I can measure the current at different RPM’s.

Do I plot V*I ; V = battery voltage; at different rpm’s or is there another method? Any help would be greatly appreciated.

"Grüße, was das Verfahren zum Erstellen einer Leistungskurve für einen 3-Phasen-Permanentmagnet Generator ist."
"Ich arbeite derzeit auf einem 8-Spule pro Phase PMA.\r\n\r\nIch weiß, wann der PMA eine Batterie die Spannung auf die Spannung der Batterie gesetzt ist."
"Muss ich Grundstück V * I; V = Batteriespannung; bei unterschiedlichen Drehzahlen, oder gibt es eine andere Methode? Jede Hilfe wäre sehr dankbar."

8PmaSide.jpg (43.4 KiB) 4408-mal betrachtet

[ncrypta]

The best would be, if you measure the voltage and ampere at different load states. So you hook up a 3-phase rectifier, and a fixed load of say 1 Ohm, then you measure at different rpm's. if you do this with different loads, and plot this you get your power rating curve at different loads you could also measure the shorted power...
Mfg Alex B.

[jb79]

As Alex said, measuring the power during the charge of a battery is not a good idea, because the output voltages always changes and the resistance of the battery is not constant.
If you measure behind a rectifier, you should have a true-rms volt/ampermeter, otherwise the value wouldn't be correct. You will also have some loss because auf the rectifier.

My proposal:
Connect phase to a seperate resistor (all resistors should have the same value) and measure the voltage/current at one of the resistors. Then multiply it by the number of phases.

[Bernd]

During my search to understand how the thing with the inner resistance of a battery works,
i get a different view than before how to calculate the power there.

I think the inner resistance of a normal big battery is very very low, around some few milliohm.
So normaly we can neglect this resistance in our calculation.

If the rectifier output voltage reaches the height of the battery voltage the loading beginns.
If we increase the rpm of the alternator, the output voltage also increase.
Caused by the extremly low inner resistance of the battery, the voltage is like nailed.

Due by the fact that the alternator still delivers it's higher voltage, this voltages above the
load begining point multiplyed by the current generates losses into the coils.

For calculation you have to know how many unloaded voltage you get after rectifer.
Also you must measure and calculate the resulting inner resistance of you alt.
In star connection it is: Resistance of all coils of one phase * 1,73.
In delta it is : Resistance of all coils of one phase / 1,73.

The formulars for the power values are :

(Voltage after rectifer minus battery voltage)² divied by the inner resistance of the alt = losses

For example: (20 volt minus 13,5 volt)² divied by 2 ohm = 6,5² / 2 = 21,13 watt losses into the coils.

Now we can calculate the amperage at this moment.
It would be I = P / U = 21,13watt / 6,5volt = 3,25 A
This amperage is into the whole circuit the same.

Power into the battery is :

Amperage * battery voltage = 3,25A * 13,5volt = 43,87 watt

The alternator delivers 43,87 watt into our battery.
At the same time we lose 21,13 watt as heat into the coils.


Bernd