gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
080715-0941 EST
tallgirl:
The main panel bus voltage has everything to do with the source impedance looking back into the grid, the equivalent source voltage that feeds that impedance, and the current positive or negative to the panel.
My guess at a 200 A service and an implication of a 200 A transformer probably should be closer to a 100 A transformer, and more source impedance to allow for a larger drop in the service drop lines.
Secondary transformer voltage is not where I would place the equivalent circuit voltage, but rather at the transformer primary where there is a relatively stiff source. Of course in the equivalent circuit you reflect this to the secondary as well as the transformer impedance.
This morning my bus voltage is a little high at 124.5 V. Loading this with 10.6 ohms reduces the voltage to 123.9 V. Thus, the load current is 11.7 A. The voltage drop is 0.6 V at 11.7 A and the source impedance is 0.051 ohms. Most of this is transformer impedance. 0.0074 ohms of this is the service drop resistance. Extrapolate this to 50 A and the voltage drop is 2.56 V. Viewed at the 240 V level the bus voltage is 124.5*2 = 249.0 and the voltage change is 5.12 V for 50 A. About 2% voltage change from a change of 50 A.
If I was running an inverter with 50 A output the bus voltage would rise to 254.12 at the 240 level, and 125.5 at the 120 level.
My typical nearly unloaded bus voltage is about 122 V.
The main panel bus voltage has to be X volts above the equivalent source voltage of the grid by Zsource*Iavailable to feed the grid. This is unrelated to the load except for the current needed to supply the load is subtracting from the current from the inverter.
I do not use many incandescent lamps, but those that I buy are rated at 130 V to improve lamp life. All my 300 W bulbs are on dimmers and seldom used at full brightness.
You indicate you generate about 12 KWH per day and buy about 5 KWH. Thus, your total usage is 17 KWH or an average of 0.7 KWH/hour. That is a yearly total of 6132 KWH. At $0.12/KWH you save about $525/year.
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tallgirl:
The main panel bus voltage has everything to do with the source impedance looking back into the grid, the equivalent source voltage that feeds that impedance, and the current positive or negative to the panel.
My guess at a 200 A service and an implication of a 200 A transformer probably should be closer to a 100 A transformer, and more source impedance to allow for a larger drop in the service drop lines.
Secondary transformer voltage is not where I would place the equivalent circuit voltage, but rather at the transformer primary where there is a relatively stiff source. Of course in the equivalent circuit you reflect this to the secondary as well as the transformer impedance.
This morning my bus voltage is a little high at 124.5 V. Loading this with 10.6 ohms reduces the voltage to 123.9 V. Thus, the load current is 11.7 A. The voltage drop is 0.6 V at 11.7 A and the source impedance is 0.051 ohms. Most of this is transformer impedance. 0.0074 ohms of this is the service drop resistance. Extrapolate this to 50 A and the voltage drop is 2.56 V. Viewed at the 240 V level the bus voltage is 124.5*2 = 249.0 and the voltage change is 5.12 V for 50 A. About 2% voltage change from a change of 50 A.
If I was running an inverter with 50 A output the bus voltage would rise to 254.12 at the 240 level, and 125.5 at the 120 level.
My typical nearly unloaded bus voltage is about 122 V.
The main panel bus voltage has to be X volts above the equivalent source voltage of the grid by Zsource*Iavailable to feed the grid. This is unrelated to the load except for the current needed to supply the load is subtracting from the current from the inverter.
I do not use many incandescent lamps, but those that I buy are rated at 130 V to improve lamp life. All my 300 W bulbs are on dimmers and seldom used at full brightness.
You indicate you generate about 12 KWH per day and buy about 5 KWH. Thus, your total usage is 17 KWH or an average of 0.7 KWH/hour. That is a yearly total of 6132 KWH. At $0.12/KWH you save about $525/year.
.