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Mayimbe:
I have no idea what your statement means or how it applies to the original post.
Since its a generator and not a motor, there is not a possibility. Kirchoff Law
First consider a simple DC generator connected to a DC motor. Make the field on both a permanent magnet. In fact just take two identical DC motors. Make one the generator initially and the other the motor.
The implication here is that the generator has mechanical power fed to its shaft. Maybe it is a water wheel. For the moment the motor is unloaded mechanically. Power flows from the generator to the motor.
The internal voltage generated in the generator is Vg. At the generator output terminals, the brushes, the voltage is V1 = Vg - Ra*Ia. In other words there is a voltage drop in the internal impedance of the generator resulting from the load current making making the output voltage lower than the generated voltage.
At the motor end there is a similar voltage drop that means the internal counter-EMF that is generated by the motor is about Vemf = Vg - 2*Ra*Ia. In turn this means the motor is running slower than the generator.
Next apply mechanical input power to the motor shaft sufficient to increase the motor shaft RPM above that of the generator and now the previous motor becomes the generator and the previous generator becomes a motor.
In this unique case put a simple diode in series with the generator to motor supply and you can prevent the back feed.
cdavis7254:
In what country are you located? Follow their rules.
Iwire has initiated some of the questions you need to consider. You really need a background in electrical circuit theory to consider the consequences of what you are describing.
I think you have said that both the backup generator and the PV are tied together and neither connects to the grid before or after the transfer switch changes state. So your real question has nothing to do with the grid. You could consider that grid does not exist.
Thus, your problem is how the generator and PV system interact with one another. This is a complex problem and will be dependent upon actual loads, overloads, failures, and what is to happen under these different conditions.
There are a lot of different questions that you need to answer. But first find out the rules for your type of proposed application. Once you know the rules, then consider all the different failure conditions and what is urgent to run under these conditions.
To illustrate my home situation. In 40 years we may have lost power three times for any extended time. The major time and problem was the northeast blackout. The probability of future failures is not high. I have a noisy 5 KW portable generator. I run it as little as possible within the night. With this size unit I can keep the basic items working in my house. These are two freezers, one refrigerator, two furnaces, and a few lights. This average load is low enough that I can for part of the day transport the generator to my daughter's house and keep it running also. How I prioritize the operation depends upon whether it is winter or summer.
In the summer my freezers are a problem because the rate of rise internally in temperature is about 6 deg/hour. So starting at 6 deg, the point where the compressor should start to cool, I have maybe 3 hours before cooling must start again. At night this means the generator has to run sometime in the middle of the night. Truly for furnace blower motors and refrigeration equipment I could work off of less than 1500 watts of peak power from an inverter and batteries. 20 KWH of energy storage would improve generator efficiency and eliminate the need to run the generator at night.
These comments are just to get you to think about questions to ask.
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