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Old 08-20-14, 07:26 PM   #61
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Solar panels are inherently DC, meaning they require an inverter for powering AC loads. The trapezoidal waveform allows the inverter to have a very high efficiency.

Actually, I looked it up and digital PFC is more common than I thought.
Energy Control - Digital Power Factor Correction

Enhanced efficiency analog PFC has a circuit that varies the cut in threshold according to load. For a fixed load (like non dimmable) lighting, that functionality would be trivial to implement. I don't know of a single chip to do it (over varying loads), but it can be implemented by adding a few opamps around a common analog PFC controller.

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Old 08-20-14, 09:27 PM   #62
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Really freaking irrelevant. Advanced analog or diminutive DSP, if the input THD < 10%, >0.99 PF, that's the end.

If VSD does not have a front end that accomplish the above, it incurs a social expense.
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Old 08-20-14, 09:48 PM   #63
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80 Plus only requires 0.9 PF (between 20% and 100% load), 0.95 for high end server PSUs. The boost stage is quite inefficient at low input voltages, so gating it off below a threshold can boost efficiency and still meet the requirement. The optimum cut in point depends on load, with lower load favoring higher cut in points.

All that matters little in residential applications when PFC adds cost to a design, residential users benefit little from it, and in most applications, PFC reduces efficiency.
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Old 08-21-14, 03:31 AM   #64
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Quote:
All that matters little in residential applications when PFC adds cost to a design, residential users benefit little from it, and in most applications, PFC reduces efficiency.
80Plus is voluntary guidelines for COMPUTER power supplies, so their specific guidelines are not applicable here.

Saving electricity from energy consumption point of view includes losses within energy provider's distribution transformer. Saving a percent of two on your BILLABLE ENERGY CHARGE by advocating a method that increases power system losses and raising net power use is doing a disservice to energy conservation and you're increasing "GWP" and "carbon foot print".

The direct losses of course would be in reduced efficiency in transformer and reduction in efficiency of other customers in your subdivision through increased harmonic imposed on voltage waveform.

Indirectly through materials and resources that must be used to upgrade or maintain infrastructure more frequently.

Have a look at this article on CFLs used in quantity rather than just taking some poster's opinion for it:

The Hidden Costs of CFLs | Will there be a price to pay for increased residential use of electronic ballasts with low power factor ratings? | Lighting & Control content from Electrical Construction & Maintenance (EC&M) Magazine

I totally support the use of embedded systems smart meter to penalize individual residential customers who do things like run 4 computers or use non-residential unfiltered VFDs and create disproportionate amount of harmonic demand relative to their kW demand.

This ensures someone with a 200W/400VA X13/ECM furnace and a computer or two is not penalized while surcharging predatory customers who contribute to substantial portions of total demand distortion on the transformer. An example is an individual customer who use 2,000kWh and using 1,400kWh of those for "at home coin farm rigs" that produce 4kVA of harmonics.

ECMs and drives present challenges for generators and make it necessary to oversize them relative to the watts they use. It is because generator is much smaller in size relative to energy provider's transformer. If the generator is as large as the subdivision's transformer, the issue is else, but such a larger generator would cost a lot more. Oh so wait, making it necessary to use larger power system equipment relative to delivered energy just increases cost for energy provider, who in turn pass it onto the rate payers.

Larger transformers also consume more power at idle.

Now, the aforementioned oversizing is the whole concept of "demand". It's generally not necessary to demand charge residential customers since there's an averaging effect in having 10-20 customers per transformer, but in rural settings where the each customer's usage has much more significant impact on transformer sizing.

You'll find that on a 1kW generator or a 1kVA transformer, a 1kW hair dryer will work fine, but not a 1hp 1kW 0.5PF 2kVA VFD pool pump with 800VA of third harmonic content.

Last edited by ICanHas; 08-21-14 at 09:04 AM..
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Old 08-21-14, 08:24 AM   #65
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Settle down guys and treat each other with respect. I don't want to have to lock threads or ban people. Thanks.

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