Power Factor Correction on Pass/FirstWatt stock/diy power amps

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Hello,

My question might be dumb, have searched and found similar title threads but no satisfying answer. So, I ask now :)

Here in France we have 230V mains. But recently, they changed the power consumption meters on all flats of the building.
Those "communicating" power meters are of a new type, Linky, green smartbox power meter said to "help us reduce of power bills". Huh.

But instead of counting kWh delivered to the client, the new green meter type does count the kVA delivered.
So, all inductive loads as motors, fluocompact bulbs, etc ...
AND, our precious class A amps that use xformers, now are metered higher than they real consuption power, thus adding a little to the bill.
I guess, on typical class A amp, metered consumption could be as high as 10-15% higher than with previous old meters ...

I think a simple way to compensate for Power Factor Correction in our amps would assure the electricity bill to be more exact,
and not paying much more than the precise real power consumption.

So, I ask now, the easy diy way : Is there a way to accurately
1°) measure real power consumption of our class A power amps
2°) calculate for mains power capacitor, in order to compensate precisely for the loss angle ?
I think this is a part of xformer structure, primary inductance, VA rating and total load on mains,
also in 230V mains xformer primary inductance might be higher than on 110V mains ...

Plus, would there be a negative side to do this ? I mean, in the audio performance,
subjective and measured. The mains here is not pure at all, sine is already distorded ...

Any input, feedback, measures, testimonials ... are welcome, please feel free to tell /share your thoughts / experience here

Kind regards,

nAr
 
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Joined 2011
I think a simple way to compensate for Power Factor Correction in our amps would assure the
electricity bill to be more exact,

The input current for most audio amplifiers is nonsinusoidal, in narrow pulses, for the usual capacitor input
rectified power supply. The effective PF can be 0.6 or so. A complex power factor correction circuit
(like in a computer power supply) is necessary to deal with this. It forces the input current waveform
to match the shape of the input voltage waveform, making the power factor 0.98 to 0.99.
 
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Buy or borrow power meter that have pf meter. Measured than try add capacitor until you get pf 0.9 - 1. Or change your xformer with pfc smps :D

At least that's what I would try :)

Can someone link me to a power meter with pf ? Here I can find a AC/DC Volts and Amps with trueRMS ... I thought that measuring one amp consumption alone on the real meter, then checking the value displayed on the Linky, would give a useable differential value ... if nothing else is wired in the flat ...

Regards,

nAr
 
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Joined 2002
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@nigelwright7557 , you will have very high power resonances in the building , cos phi 0,5 inductive. In all High-rise Buildings Elevator using big Machines up to 350kW and Motors are highly inductive so the Compensation Capacitor Banks need to be very close and terminated with proper calculated chokes. If not your Transformer station will be melt or under fire , Supply cables will be melded for sure!
Just using Capacitors is not correct to react the heavy load changes during acceleration or regenerated backwards energy.
Correct is when using Capacitors connect in Delta and controlled by thyristors and that’s the only well working solution.
 
You should find the power factor of FW amps to be about 80%.

Hi Nelson, thanks for your answer. So if I understand, I can save up 19% of my "audio power" electricity bill, if compensate the xformers right ?

@nigelwright7557 , you will have very high power resonances in the building , cos phi 0,5 inductive. In all High-rise Buildings Elevator using big Machines up to 350kW and Motors are highly inductive so the Compensation Capacitor Banks need to be very close and terminated with proper calculated chokes. If not your Transformer station will be melt or under fire , Supply cables will be melded for sure!
Just using Capacitors is not correct to react the heavy load changes during acceleration or regenerated backwards energy.
Correct is when using Capacitors connect in Delta and controlled by thyristors and that’s the only well working solution.

Here in our class A amps, with linear power supply and simple toroid, the voltage and current draw are mostly the same once powered up. There seem nothing complex to deal with, such as high rise building elevator complex motor machinery ... Nothing that would justify using additional chokes / thyristors / delta capacitor bank scheme

Regards,

nAr
 
Power factor

Ideal power factor is 1.00. This is the case where kVA=kW. There are two main factors to a power factor less than unity. First is displacement - the phase shift between voltage and current (the cos phi previously mentioned). Both are sinusoidal, but offset in phase. This is typically seen in industrial settings with large motors. Capacitors are used here to counteract the lagging power factor of the motors. The second factor is distortion. This is the degree to which the current waveform does not look like the voltage waveform. The voltage is sinusoidal, but the current is a series of pulses, two per AC cycle. Non-PFC power supplies will only take current near the peaks of the AC waveform when the diodes turn on to replenish the bulk capacitors. Adding capacitance across the line will not help the power factor, it may in fact create other problems.
 
Perhaps it would be best to use a choke input filter for the power supply.
Older tube power supplies did this to avoid losses in the rectifiers.

If you are powering a class A amplifier, you do not have to worry about minimum inductance as much like you would with a class AB amplifier.
Minimum inductance would be supply voltage divided by supply milliampres.

Advantages are:
Somewhat better power factor.
Avoids large current spikes which can cause noise problems.
Cooler running transformer, rectifiers.

Disadvantages:
Input choke may be fairly large and possibly noisy if not potted.
 

PRR

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Line caps will not "compensate" a peak-catching DC rectifier (as it does for simple inductive motors). The waveshape is too wacky for simple solutions.

Tube heaters will be unity PF. (Ah, wrong section.)

As Davin says, choke-input DC rectifier will be near unity PF. This may be one reason choke-input is used in seriously large systems (50KW AM transmitters, also some metal-melting). Problem is finding and shipping chokes near as large as your power transformers. "Ordinary" chokes may not be rated for LARGE AC voltage across the ends, so you may have to over-buy.

The "modern hi-tech" way is to follow the wave and invert-convert moment-by-moment to deliver the DC output while presenting a Sine-like current wave to the power company. There's chips for this. They are not DIY-friendly (unless someone here day-jobs in a PFC design shop).

Ask yourself just how much is it *worth*? If a 10 Watt audio amp eats 30 Watts of actual Power but 100 VA of total energy, I'd figure that as $0.02 per hour to feed my pleasure. This is far cheaper than drinking. And apparently cheaper than any PF-reduction technique. Yes, if I were fond of 500 Watt amps, it gets to $1/hour-- not cheap, but cheaper than almost any other pleasure. But my numbers may be way off, so figure it for your amps and rates.
 
`Hi all,

So, update to the thread. I just got my mains power meter to do some tests on one of my diy monoblocks Aleph J.

On startup, the measures :
131,0 W / 179,0 VA / 0,73 Cos_Phi

After one hour, after warm-up :
118,8 W / 164,1 VA / 0,72 Cos_Phi.

After 2 hours, once idle :
118W / 164 VA / 0,71 Cos_Phi.

Seems that with a stereo set, differential value between Watts and VA will be about 90 kVAR am I wrong ?

I got those big Non Polarized capacitors, ;) Sic Safco 1050V / 10uF that I'd like to try parallel to 230V power input of the amp. Then I'd measure again the power factor ...

I can go up to 40 uF, as I can get a total of 4 of those cans. I think they're oil type, pyralene based I guess. They measure great and cans are perfectly sealed, in perfect condition ... :cool:

Best regards,

nAr
 

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I see that if you multiply the measured VA by the measured cosphi you get a very good correlation to the W used.
I think we pay for the watts used with our normal domestic watthour meters.
i.e. we get the extra non sinusoidal/out of phase current for free.
Even though the heat in our PSU is related to the paid for current plus the extra current.
 
Nope !!! Alas, here in France with the new inwall power meters called Linky, green color (...) we are now charged for kVA used, and not for kWh anymore ... Shame but nothing else to do about Linky ... They changed power meters without user's consent :-\
Regards,
nAr
 
They don't need your consent to measure and charge you for the current you are using.

Households were such a small part of consumption that it was not worth the electricity suppliers efforts to install VA meters that we got away with poor power factor consumption for decades.

We can't complain if modern technology allows them to charge appropriately.

If they recover the costs of true current consumption, then overall their prices should actually drop. Then we get the benefit. The extra cost is the replacement of all the meters.
 
They don't need your consent to measure and charge you for the current you are using.

Households were such a small part of consumption that it was not worth the electricity suppliers efforts to install VA meters that we got away with poor power factor consumption for decades.

We can't complain if modern technology allows them to charge appropriately.

If they recover the costs of true current consumption, then overall their prices should actually drop. Then we get the benefit. The extra cost is the replacement of all the meters.

Dear Andrew, I would agree with you if it was true; but they stated meter change wouldn't cost anything, and the only thing that has changed is the power bill, that didn't drop of course, but went up accordingly ... To the kvA used and not the kWh as before.

Regards,

nar
 
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