Re: Power factor (was genset trailer)

["1sclunn" <1sclunn@msn.com>]

snip'''. Technically it's not
the same "Power factor" as when you supply AC to the light bulb
through a capacitor. In this case current and voltage are perfect
sin waves, no peaks, and still poor power factor because there is
phase shift between the two.
Steve clunn wrote
I hooked up some capacitors  that way with a bridge rectifier in place of
the light bulb and some batteries on the dc side of the bridge . I was
surprised to find that when the input voltage went up the current went up
but not like it would  when you raise the voltage on a battery being
charged. ex. when charging a battery at 13.5 if one raise the voltage 1 volt
the amps poor in .  with the cap in line (ac side) doubling the voltage only
increased the amps a bit (I don't remember how much) . I was charging my
120v car on 240v(ac) and was controlling the amps by adding caps
(air-conditioned motor caps) . three things I noticed and then scraped the
hole thing.
1. the amps flowing into the car(on e-meter) were the same as at the pole(I
turned the hole house off and checked as it seemed funny ,were did the other
half of my 120 go(:(  cheap o clamp on amp meter) . I was acting like a big
resistor .
2 . the thing went right by 150 volts ,this is were it usually would taper
off . When I checked on it the voltage was 160 and 8 amps about . when I
started the charge the amps weren't that high like around 12
3. the lights in the shop seemed brighter when I plugged it in
I don't under stand exactly what was happening . was I feeding  back to the
grid the same amps as the car was seeing just out of phase?----- Original
Message -----
From: "Victor Tikhonov" <vtikhono@lsil.com>
To: <ev@listproc.sjsu.edu>
Sent: Monday, July 29, 2002 12:25 PM
Subject: Pover factor (was genset trailer)


> Peter VanDerWal wrote:
> >
> > A bridge rectifier on single phase AC creates a pulsating DC.  Current
only
> > flows when the voltage rises above the battery voltage.  (warning crude
> > ASCII art)
> >
> > Voltage wave form
> >
> >     ^        ^
> > ---/-\------/-\----------------------------  Battery Voltage
> >   /   \    /   \
> >  /     \  /     \
> > /       \/       \
> >
> > Current wave form
> >
> >     ^       ^
> >    / \     / \
> >    | |     | |
> > ___| |_____| |__
> >
> > The spiky current wave form doesn't match the voltage waveform (hence
poor
> > power factor).
>
> Peter, what you described technically applies to 3 phase as well:
>
>
>
>  ---/\-/\-/\-/\-/\----------------------------  Battery Voltage
>    /  X  X  X  X  \
>   /  /  X  X  X \  \
>  /  /  /  x  X \ \  \
> /  /  /  /  / \ \
>
>
>  Current wave form
>
>
>    || || || || ||
>    || || || || ||
>  __||_||_||_||_||__
>
> Still peaks of the current, but at very top of each sign wave.
> Plateau of the top of the wave is large and 3 phase overlap so
> often, that if battery voltage gets lower, indeed pure DC starts
> flowing.
>
>
>
> > With three phase, because of the way the phases interact, when you
rectify
> > it with a 6 diode bridge you get pure DC out.  Pure DC voltage, pure DC
> > current and both current and voltage are perfectly in phase.
> >
>
> In your single phase picture they are also perfectly in phase -
> there is no leading or lagging. The max current peak (in time) coincide
> with max voltage point, so they are in phase. Technically it's not
> the same "Power factor" as when you supply AC to the light bulb
> through a capacitor. In this case current and voltage are perfect
> sin waves, no peaks, and still poor power factor because there is
> phase shift between the two.
>
> THese are two distinctive cases and in both we call it "power factor",
> but one should realize the fundamentals (and thus solutions) are very
> different.
>
> > > Who says there are no power factor control problems with
> > > three phase?   Tell us more about that.
>
> I believe the original author meant the voltage spikes (because
> poor brushes contact, whatever), not peaks, are problems
> for 3 phase generators, and so just as dangerous for PFC-50
> as spikes (from lightening, not because bay-boy-type current peaks)
> in single phase supply.
>
> Victor
>
> > > Tom Shay
> > >
> > > ----- Original Message -----
> > > From: "VanDerWal, Peter MSgt" <vanderwp@fhu.disa.mil>
> > > To: "'EV List'" <ev@listproc.sjsu.edu>
> > > Sent: Friday, July 26, 2002 2:26 PM
> > > Subject: Re: no-man's-land genset trailer
> > >
> > >
> > > (stuff snipped out)
> > >
> > > > Or save the cost of the PFC charge and buy a three phase 10kw
generator
> > > for
> > > > $3700 and just use a 6way bridge (no PFC problems with three phase).
> > 10kw
> > > > (approx 80 amps) will almost let you drive continuously. 350lbs and
it
> > > says
> > > > it's "Super Quite".
> > > > http://www.electricpowergenerator.com/threephase.html
> > > >
> > > >
> > >
> > >
>
>