Trying to deeply investigate LED pulsing flickering with HF off-grid inverters
- Thread starter fmeili1
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fmeili1
Solar Enthusiast
After a bit more investigation I think the HF inverters (or at least the EG4-6500EX) are more sensitive about bad power factors. It looks like my old slot machine using a huge classic rectifier circuit with a big capacitor which produces a lot of phase shifted current harmonics which results in a bad power factor which is about 0.6 and a simple passive PFC will not work in this case.
Next week I will try to do some tests with a complete decoupled connection of the slot machine to my mains (via an online double conversion UPS). In case this will be successful, I'll try to do some additional tests with an active PFC circuit to learn more about these type of problems and possible solutions.
I've looked a bit deeper into the specs of the EG4-6500EX to find out something about apparent power - but nothing really useful.
Next week I will try to do some tests with a complete decoupled connection of the slot machine to my mains (via an online double conversion UPS). In case this will be successful, I'll try to do some additional tests with an active PFC circuit to learn more about these type of problems and possible solutions.
I've looked a bit deeper into the specs of the EG4-6500EX to find out something about apparent power - but nothing really useful.
- Right at the beginning of the EG4-6500EX users manual there is the following headline:
EG4 6500 EX-48
SOLAR INVERTER/CHARGER
6.5KVA 120V AC
This is the only place in the manual where VA is mentioned as apparent power. - In the specifications table there is only 6500W mentioned as Rated Output Power, no more hints about a possible difference between apparent power (VA) and true power (W)
- SolarAssistant is showing both 6500W for true power and 6500VA as apparent power int the settings specification section which SA gets from the inverter itself via modbus - but I think, this can't be true because the true power is usually always at bit less than the apparent power. Most inverter brands specify both values separately.
fmeili1
Solar Enthusiast
The user @nkhorman made a very interesting measurement with a 2-channel oscilloscope showing the EG4-6500EX output while some LEDs are pulsing (different topic):
EG4 6500EX Voltage/Frequency Fluctuations #1
EG4 6500EX Voltage/Frequency Fluctuations #2
Do you think this is the underdamped system behavior you describe to prevent overshoot, or is this something else?
Hard to tell just from looking at the waveform. Does it flicker when inverter is running alone and not paired with 2nd inverter? Problem could be related to paralleled mode of operation possibly due to synchronization data latency causing voltage overshoot.
I'd have to bypass, and break the pairing to try... something I could do, but.... It's in operational use... didn't really want "go backward".
But I guess I'll have to do that eventually.
Sigh.
It wouldn't be a big a deal if I didn't have a 240v well pump load.
I guess I'll shut off that load breaker and give it a shot when I have time.
A little more scope capture this morning, EG4 6500EX Voltage/Frequency Fluctuations #3.
The previous two videos where with the units in SBU mode.
In this one, the units are in USB mode with, PV, 120v load on both phases, and some intermitent 240v load (well pump).
Is this kind of behavior really expected and/or normal for HF ?
The previous two videos where with the units in SBU mode.
In this one, the units are in USB mode with, PV, 120v load on both phases, and some intermitent 240v load (well pump).
Is this kind of behavior really expected and/or normal for HF ?
The issues that I see are some intermittent transients, and the waveform seems to be clipping the tops of the waveform. I don't know if it's normal, but could the transients be when the well pump turns on/off. I could imagine a large inductive load causing such transients in a HF inverter. I don't know what would be causing the clipping, though.
Hedges
I See Electromagnetic Fields!
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I've seen grid waveform clipped, sine wave with flat tops.
It was at a factory in Guadalajara with rows and rows of X-boxes being tested. (well, may have been on UPS due to grid power issues.)
When load is rectifier/capacitor front end, zero current is drawn until AC voltage exceeds capacitor, then capacitor presents a short. So flat tops.
Try resistive loads. Try inductive loads (with no SMPS or LED lamps.)
It was at a factory in Guadalajara with rows and rows of X-boxes being tested. (well, may have been on UPS due to grid power issues.)
When load is rectifier/capacitor front end, zero current is drawn until AC voltage exceeds capacitor, then capacitor presents a short. So flat tops.
Try resistive loads. Try inductive loads (with no SMPS or LED lamps.)
176v?
andrew-d
New Member
What we call 120V AC is actually 170V at peak; the name "120V" is actually the "root mean square" (RMS) voltage. Long story short, a sine wave at 60Hz with voltage peaking at 170V (referred to as "Vp") is equivalent to 120V DC in terms of power dissipation, which is why it's called that.
Another way to think about it: while the sine wave peaks at 170V, we only have 120V that can actually do work. If you hook a 120V DC power supply up to a resistor, it'll generate some amount of heat. If you hook an AC power supply up to that same resistor, configured to output a peak of 120V (not RMS), then it'll generate less heat than with the 120V DC power supply! An AC supply with a peak of 170V will produce the same amount of heat ("power dissipation") as a 120V DC power supply, for that same resistor. For more details:
RMS Voltage and Current- Explained
This is an article that explains what rms voltage and current is, real life examples of it, and how RMS power can be calculated.
www.learningaboutelectronics.com
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