Portable Device Chargers - Terrible Wastes of Energy

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JamesW said:
Pumps using a capacitor should have a power factor of about 1.0.
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VS pumps maybe but pumps with induction motors have a power factor that varies with load. Usually induction motors don't get much about 0.8-0.9 PF at maximum. This will drop off with an operating point that moves to the left of the head curve.

For industrial applications, they will sometimes add a capacitor bank to shift the line current so the facility has a PF of one but that is mandated by the power company. They generally don't require that for residential power.

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No. Start capacitors are only engaged during the start process and although run capacitors do help with power factor and efficiency, they only affect the starting winding. There is no capacitor on the main winding so the load is still inductive. And that reactance changes with load so you would need a variable capacitor to change with it in order to compensate over a variance in load.

As for the kilowatt, that would be a surprise to me because low HP motors tend to have fairly poor PFs so I might be inclined not to trust the measurement. I would use a voltage and amp scope to measure the phase shift between the two to confirm. The pump/motor you measured may have and operating point close to the best efficiency point where the PF is a maximum but again, I would be surprised if it was much above 0.9. What was the pump make/model?
 
The Kill-a-Watt I have can only go up to 1800W. I would not think to put it on a pool pump....maybe a really small pool pump.

As for PF & load, I did see that with the fridge. Anytime the compressor would start, the PF would drop and then slowly climb back up nearer 1.0. I even saw that with my Keurig Coffee maker - when the heater would kick in to keep the reservoir warm, the PF would drop. Also, when the dispensing motor would run to push water out through the brewing cup, the PF would drop and recover.
 
CSCR and PSC motors have the capacitor on the start winding:

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Also to compensate for the induction, the capacitor has to be in parallel with the inductor and not in series.


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JamesW said:
In the PSC diagram, it looks like the capacitor is in parallel?
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Not quite. The capacitor is in series with the starter winding. So it will have a minor impact on power factor but I doubt it would fully compensate for the induction.
 
Teald024 said:
Why no try? I used my P3 to test the power consumption of my nameplate rated 2hp pump on LS. It only pulled around 250 Watts. HS was up near 1100 Watts if I remember correctly.
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While it might be fun to test, all of my pumps are hard-wired into my automation panel. So I'd need a different way to test it.

Installing a Neurino in the Pentair EasyTouch cabinet would be neat....

Neurio W1-HEM Home Energy Monitor (North American Version) https://www.amazon.com/dp/B0149EE5KS/ref=cm_sw_r_cp_api_PGzOzbFX24GMK
 

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JamesW said:
The capacitor is in series with the start windings. It looks like the capacitor and start windings are both in parallel with the run windings.
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That's correct but that capacitor is designed to provide a small phase shift in the starter winding. It doesn't mean that it will fully compensate for both windings induction especially over varying loads. Simply having a capacitor is not enough. A run capacitor size is designed to provide a phase shift between the main and starter windings so by definition, it doesn't compensate for the total inductance of both windings. The efficiency gain of a run capacitor is because the start winding is used to provide additional power to the rotor continuously where a CS motor starter winding would normally remain idle and have inductive losses.


But I wanted to check the kill-a-Watt accuracy on PF so I did a test on a PSC motor (unloaded) that I had and the PF measured by the kill-a-watt was 0.4 and measured by the scope meter was 0.3 or over a 30% error.

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I can repeat the scope measurement on my jet pump which is also a PSC motor.
 
Below is a video of the scope as the pump primes. When it starts out the motor has about a 2.5 msec V-I offset or a PF of about 0.59 then it decreases to about 1 ms or a PF of about 0.93 which is pretty good but not perfect.

 
Nice demonstration!!

Also, neat portable scope. Those little guys are super expensive. However, when I was a working man doing lab work, we had several $50,000+ digital programmable oscilloscopes that could do FFTs and other advanced signal processing on the fly. Always floored me to think the scope I was playing with costs more than any car I've ever owned....
 
It was a bonus for running a test lab a couple of decades ago. ;)

Also, I did a test with my main pump which is a 1/2 HP impeller on a 1 HP URHP motor so the motor is a bit oversized. The PF for that was 0.6 on high speed and 0.5 on low speed.
 
Wowsa, more info than I can ingest.

Going back to the opening post I was reminded of comments made in a locally produced home show. They said that PED chargers used power when plugged in but not connected to the PED. - Really, could that be true? So I got my cheap voltage meter out and busted... No PED, no power draw. It's clear that at least one of these popular home shows don't bother to test their claims. I wonder how common that is?
 

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