Power factor correction
Tim Williams
better. But forward sucks over wide duty cycle ranges. What do they do,
just bigger flybacks? Nothing at all?
Tim
--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
Jan Panteltje
<tmor...@charter.net> wrote in <Yhn_m.18015$wC3....@newsfe07.iad>:
For much higher power 3 phase rectifiers are used.
That leaves only a small ripple.
I am not sure if you need PFC in such a case.
Phil Allison
"Tim Williams"
> PFC is a flyback thing.
** Come back when you sober up.
Fuckhead.
... Phil
MooseFET
> PFC is a flyback thing. But flybacks suck over 100W, where forward looks
> better. But forward sucks over wide duty cycle ranges. What do they do,
> just bigger flybacks? Nothing at all?
At modestly larger that 100W the flyback booster method still works
ok. The bulk of the power is transfered by the booster when its boost
ratio is small. To handle the very wide duty cycle dropping the
frequency as the mains nears its peak works.
Multiple boosters running out of phase will let you go up to higher
power levels and the ripple tends to cancel.
Other designs do use various sorts of forward converters. No matter
what you do, you need to have a core somewhere that has a significant
energy storage. To make the forward converter method work, the output
side inductor has to do the storing. Going up in frequency, keeps the
inductor's mechanical size smallish.
Hammy
<tmor...@charter.net> wrote:
>PFC is a flyback thing. But flybacks suck over 100W, where forward looks
>better. But forward sucks over wide duty cycle ranges. What do they do,
>just bigger flybacks? Nothing at all?
>
>Tim
They use CCM Boost topology for PFC.
See NCP1654 for example.
Hammy
Fred Bartoli
> PFC is a flyback thing. But flybacks suck over 100W, where forward looks
> better. But forward sucks over wide duty cycle ranges. What do they do,
> just bigger flybacks? Nothing at all?
>
> Tim
>
Flybacks work great in PFC but have pulsed input current which isn't so
great.
The usual PFC is a boost, but you don't get isolation and have to manage
inrush current.
I once did a 250W isolated sepic PFC with zero input ripple.
Worked great with none of the above pb.
I think I've made a couple of posts here. 't was circa 2001-2002.
--
Thanks,
Fred.
Tim Williams
news:hhd149$b7b$1...@news.albasani.net...
> For much higher power 3 phase rectifiers are used.
> That leaves only a small ripple.
> I am not sure if you need PFC in such a case.
Maybe, maybe not. You get 60 degree conduction, which isn't quite 90, so
maybe it would benefit some. Where cap input filters are used, conduction
can still be narrower and peakier.
What I'm most interested in is single phase, since there's a small band
between 2kVA-20kVA where single phase is available. My welder runs from a
240V, 50A circuit, for instance. Just imagine how many home machinists have
their shops wired with, say, a 240V 100A circuit, and have all their
machines running from a rotary phase converter because nobody mades single
phase motors over 1-2 HP. Three phase simply isn't an option for
residential in the U.S..
So I guess flyback (well, boost) is still the way to go? Just more phases?
Three phase I suppose would be a good start for this power level? I don't
like the idea of CCM, even at 200kHz those inductors will be bigger than the
rest of the circuit after it!
MooseFET
> "Jan Panteltje" <pNaonStpealm...@yahoo.com> wrote in message
>
> news:hhd149$b7b$1...@news.albasani.net...
>
> > For much higher power 3 phase rectifiers are used.
> > That leaves only a small ripple.
> > I am not sure if you need PFC in such a case.
>
> Maybe, maybe not. You get 60 degree conduction, which isn't quite 90, so
> maybe it would benefit some. Where cap input filters are used, conduction
> can still be narrower and peakier.
>
> What I'm most interested in is single phase, since there's a small band
> between 2kVA-20kVA where single phase is available. My welder runs from a
> 240V, 50A circuit, for instance. Just imagine how many home machinists have
> their shops wired with, say, a 240V 100A circuit, and have all their
> machines running from a rotary phase converter because nobody mades single
> phase motors over 1-2 HP. Three phase simply isn't an option for
> residential in the U.S..
>
> So I guess flyback (well, boost) is still the way to go? Just more phases?
> Three phase I suppose would be a good start for this power level? I don't
> like the idea of CCM, even at 200kHz those inductors will be bigger than the
> rest of the circuit after it!
You can make the current go continuous at the peaks and discontinuous
at lower points. It makes the control a bit harder but makes the
inductor a lot smaller.
You can also make the frequency rise as you go to the lower voltages.
The frequency and inductance can be optimized for near the peak
voltage. Since this is where most of the power transfers, the
efficiency is dominated by it. You can then raise the frequency as
you go to lower voltages to semi-optimize at each voltage point.
Tim Williams
news:3ae8196e-a5ee-418b...@d20g2000yqh.googlegroups.com...
> You can also make the frequency rise as you go to the lower voltages.
> The frequency and inductance can be optimized for near the peak
> voltage. Since this is where most of the power transfers, the
> efficiency is dominated by it. You can then raise the frequency as
> you go to lower voltages to semi-optimize at each voltage point.
I was looking at the FAN9611 the other day. BCM is nice because it uses
"all" the inductor's capacity. Now, the datasheet says it's useful for
100-1000W, but do you think it'd be good for another decade beyond that?
What scares me is the frequency clamp stops at "only" 520-750kHz. I don't
think I want to deal with that much dV/dt and dI/dt just yet...
It doesn't look like Fairchild is making more than biphase chips... TI has
the UCC28070 which looks fairly equivalent (with constant frequency
instead). Offhand, I'm not finding anything with more than two phases.
MooseFET
> "MooseFET" <kensm...@rahul.net> wrote in message
>
> news:3ae8196e-a5ee-418b...@d20g2000yqh.googlegroups.com...
>
> > You can also make the frequency rise as you go to the lower voltages.
> > The frequency and inductance can be optimized for near the peak
> > voltage. Since this is where most of the power transfers, the
> > efficiency is dominated by it. You can then raise the frequency as
> > you go to lower voltages to semi-optimize at each voltage point.
>
> I was looking at the FAN9611 the other day. BCM is nice because it uses
> "all" the inductor's capacity. Now, the datasheet says it's useful for
> 100-1000W, but do you think it'd be good for another decade beyond that?
> What scares me is the frequency clamp stops at "only" 520-750kHz. I don't
> think I want to deal with that much dV/dt and dI/dt just yet...
You can never trust the makers "good for from here to there" on
controller chips.
The limitation is largely the result of how much current the outputs
can produce.
They assume "reasonable" values for the gate charge per drain current
rating of
the MOSFET and work out how much current that comes out to.
As new MOSFETs are introduced, the ranges become sort of nonsense.
> It doesn't look like Fairchild is making more than biphase chips... TI has
> the UCC28070 which looks fairly equivalent (with constant frequency
> instead). Offhand, I'm not finding anything with more than two phases.
The amount of advantage decreases with increasing number of phases.
You can always make N copies of the 2 phase circuit to get N times the
power. Making them share isn't going to be too hard to do.
Jon Elson
> What I'm most interested in is single phase, since there's a small band
> between 2kVA-20kVA where single phase is available. My welder runs from a
> 240V, 50A circuit, for instance. Just imagine how many home machinists have
> their shops wired with, say, a 240V 100A circuit, and have all their
> machines running from a rotary phase converter because nobody mades single
> phase motors over 1-2 HP. Three phase simply isn't an option for
> residential in the U.S..
For home shop use, a VFD can't be beat. You get variable speed, soft
start and dynamic braking. Running a 5 Hp + 3-phase machine motor off
one of those "phase converters" will sure dim your lights on every
start. An RPC is better, but makes noise and sucks power all the time
it is running. Neither gives you braking. if you have a big lathe with
no mechanical clutch/brake setup, the long coast time can be an actual
safety concern. My 15" Sheldon lathe would coast 20 seconds by itself,
but stops in 3/4 second by the VFD.
>
> So I guess flyback (well, boost) is still the way to go? Just more phases?
> Three phase I suppose would be a good start for this power level? I don't
> like the idea of CCM, even at 200kHz those inductors will be bigger than the
> rest of the circuit after it!
The typical larger PFC scheme uses a boost converter that is modulated
by the voltage waveform, so the current draw matches the instantaneous
voltage, scaled by average current demand. This stage precedes the main
converter, which would usually be a push-pull design, and you can use
the topology and drive scheme of your choice in that converter.
Jon
Alan W
> PFC is a flyback thing. But flybacks suck over 100W, where forward looks
> better. But forward sucks over wide duty cycle ranges. What do they do,
> just bigger flybacks? Nothing at all?
>
> Tim
>
I've done a 2kW CCM PFC using a boost converter - the inductor was
pretty massive (several pounds at least), but then again it was running
at 50 kHz. (It was DSP-based, so the control loop couldn't run much faster.)
It was for a 2HP VFD, and there wasn't any size or weight constraint,
otherwise I would have figured out how to use a higher frequency with a
smaller inductor.
I seem to remember Bi Technologies made some power modules designed for
PFC converters in the 2-3kW range, and had some app notes for them.
- Alan
Tim Williams
news:JridnVJ_VK2HRqbW...@giganews.com...
> For home shop use, a VFD can't be beat.
Unless you're cheap, which most of rec.crafts.metalworking IS. ;-) When
you get a lathe for $200 and a case of beer, VFDs don't look so cheap.
They're definitely nice though.
As for electrical characteristics, VFDs are a fine example: what do they do
for PFC? Nothing? The VFDs installed in the school's power lab are 10 or
15HP, three phase input, and according to the Fluke PQAs, current is spikey
as hell, no PFC, big gulps of capacitor charging. Doesn't seem very nice to
me, and when you're losing half your VAs in harmonic current, it's just not
practical from a single phase supply.
> The typical larger PFC scheme uses a boost converter that is modulated by
> the voltage waveform, so the current draw matches the instantaneous
> voltage, scaled by average current demand. This stage precedes the main
> converter, which would usually be a push-pull design, and you can use the
> topology and drive scheme of your choice in that converter.
Yeah, but that doesn't work well at let's say 400V and 30A. The inductor is
huge, and it's an awful lot of ripple on the capacitors. There's gotta be a
better way (multiphase helps).
JosephKK
>PFC is a flyback thing. But flybacks suck over 100W, where forward looks
>better. But forward sucks over wide duty cycle ranges. What do they do,
>just bigger flybacks? Nothing at all?
>
>Tim
What? Even i have done flyback at about 15 W and have heard of them used in
the 10s of milliwatt range. I think i have seen PFC that was done with SEPIC
in the 20 watt range.
JosephKK
I am playing around with modeling 3-phase rectifiers. I think PFC
would be a real good thing for 3-phase rectifiers. May be more than
a tad interesting to implement though.
I am getting some interesting results. I would really like to
build some and measure them.
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JosephKK
Not only that, i tripped over an alternate reading.
Paul Keinanen
<pNaonSt...@yahoo.com> wrote:
The ordinary 3 phase 6 pulse rectifier is a quite nasty polluter of
the mains.
To reduce the harmonics, 12 pulse rectifiers have been used, with one
set of rectifiers connected to the wye windings and the other set from
separate delta windings. For high power systems, you still are going
to need a medium/low voltage transformer on site, so it is not a big
deal having separate wye and delta secondary windings on that
transformer.
If you want to get away with the heavy 50 Hz transformer, there seems
to be various more or less patented 3 phase systems using flyback etc.
systems to reduce the PFC, but these seems to be hugely complex and
have special floating requirements for the DC side.
If floating output or voltages other than those obtainable by simple
rectifiers are required, it might be easier to simply get three single
phase SMPS with PFC at the input and connect the DC outputs in
parallel.
If the input voltage ratings permit, instead of wye, connect the
inputs into delta to avoid any mains neutral polluting and also allow
higher voltage and hence higher power (1.7x) for a specific
semiconductor amperage.
Fred Bartoli
For Tim, which I suspect is asking this for his induction heater, it
might be easier to use his bridge so as to draw sine current.
The output power will be sine squared but who cares? And that'll put
more requirement on some components for the same average output power,
but it'll avoid a full PFC stage which won't do good on efficiency, and
this might have a higher overall efficiency.
--
Thanks,
Fred.
Tim Williams
news:4b41b520$0$30367$426a...@news.free.fr...
> For Tim, which I suspect is asking this for his induction heater, it might
> be easier to use his bridge so as to draw sine current.
Yup. But it's also a good general question.
> The output power will be sine squared but who cares? And that'll put more
> requirement on some components for the same average output power, but
> it'll avoid a full PFC stage which won't do good on efficiency, and this
> might have a higher overall efficiency.
I may do this, and it even makes the coil hum with a pleasing growl. The
downside is it puts 120Hz into all my loop, and makes scoping the inverter
fairly useless. Constant current mode would have to be slower than 120Hz,
and I'm not sure how 120Hz will affect the PLL.
Jan Panteltje
<kein...@sci.fi> wrote in <q4v2k5hqkr88dmmja...@4ax.com>:
Yes, the ones I have dealt with also had a huge heavy inductor beteen the rectifiers and the filtercaps.
L
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| | | |
-------------------------------------------------- -
The inductor smoothes the main current, and reduces capacitor ripple current.
For something like 4kVA and up.
MooseFET
> On a sunny day (Mon, 04 Jan 2010 07:53:30 +0200) it happened Paul Keinanen
>
>
>
> >On Tue, 29 Dec 2009 13:44:36 GMT, Jan Panteltje
> ><pNaonStpealm...@yahoo.com> wrote:
>
> >>On a sunny day (Tue, 29 Dec 2009 07:17:31 -0600) it happened "Tim Williams"
With the coil, the current is near constant. This makes the harmonic
content less
but still significant. Adding a moderate sized transformer at each
phase and doubling
the number of diodes will lower the harmonics quite a bit.
Basically it is 3 of these
------------------ To bridge
(
A----------
(
------------------ To bridge
B-----------
)
)
)
C-----------
Since the voltage between B and C is at 90 degrees to the voltage from
A
to ground, the voltage on the secondary only needs to be the tan() of
the
angle you are shifting the phase by.
tan(15)=0.27
Jan Panteltje
<kens...@rahul.net> wrote in
<2562a20f-e214-4701...@a15g2000yqm.googlegroups.com>:
>On Jan 4, 4:29�am, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:
>> On a sunny day (Mon, 04 Jan 2010 07:53:30 +0200) it happened Paul Keinane=
>n
>> <keina...@sci.fi> wrote in <q4v2k5hqkr88dmmja3fssrc7o7cdrnp...@4ax.com>:
>>
>>
>>
>> >On Tue, 29 Dec 2009 13:44:36 GMT, Jan Panteltje
>> ><pNaonStpealm...@yahoo.com> wrote:
>>
>> >>On a sunny day (Tue, 29 Dec 2009 07:17:31 -0600) it happened "Tim Willi=
>ams"
>> >><tmoran...@charter.net> wrote in <Yhn_m.18015$wC3.5...@newsfe07.iad>:
>>
>> >>>PFC is a flyback thing. �But flybacks suck over 100W, where forward =
>looks
>> >>>better. �But forward sucks over wide duty cycle ranges. �What do t=
>> Yes, the ones I have dealt with also had a huge heavy inductor beteen the=
> rectifiers and the filtercaps.
>> � � � � � � � � � � � � � � � � �L
>> � � � � � � � � � � � � � � � =====
>=====
>> � � �-------------------------^^^^^^^^^---------------- +
>> � � | � � � | � � � | � � � � � � � � �=
> � � � � � |
>> � �--- � � --- � � --- � � � � � � � � � =
>� � � � �|
>> � �/ \ � � / \ � � / \ � � � � � � � � � =
>� � � � �|
>> � �--- � � --- � � --- � � � � � � � � � =
>� � � � �|
>> � � | � � � | � � � | � � � � � � � � �=
> � � � � � |
>> --- | � � � | � � � | � � � � � � � � � �=
> � � � � |
>> � � | � � � | � � � | � � � � � � � � �=
> � � � � �===
>> --- ) ------| � � � |
>> � � | � � � | � � � | � � � � � � � � �=
> � � � � �--- C
>> --- ) ----- ) ----- | � � � � � � � � � � � � �=
> � |
>> � � | � � � | � � � | � � � � � � � � �=
> � � � � � |
>> � �--- � � --- � � --- � � � � � � � � � =
>� � � � �|
>> � �/ \ � � / \ � � / \ � � � � � � � � � =
>� � � � �|
>> � �--- � � --- � � --- � � � � � � � � � =
>� � � � �|
>> � � | � � � | � � � | � � � � � � � � �=
> � � � � � |
>> � � �-------------------------------------------------- -
>> The inductor smoothes the main current, and reduces capacitor ripple curr=
>ent.
>> For something like 4kVA and up.
>
>With the coil, the current is near constant. This makes the harmonic
>content less
>but still significant. Adding a moderate sized transformer at each
>phase and doubling
>the number of diodes will lower the harmonics quite a bit.
>
>Basically it is 3 of these
>
> ------------------ To bridge
> (
>A----------
> (
> ------------------ To bridge
>
>B-----------
> )
> )
> )
>C-----------
>
>
>Since the voltage between B and C is at 90 degrees to the voltage from
>A
>to ground, the voltage on the secondary only needs to be the tan() of
>the
>angle you are shifting the phase by.
>
>tan(15)=0.27
An interesting solution, never seen that before, maybe I am too old:-)
Tim Williams
> With the coil, the current is near constant. This makes the harmonic
> content less
> but still significant. Adding a moderate sized transformer at each
> phase and doubling
> the number of diodes will lower the harmonics quite a bit.
>
> Basically it is 3 of these
And of course, since you have two phases on two wires (let the other be
common), you have a linearly independent basis (not orthonormal, but so
what) from which you can span the entire vector space of voltage and phase.
So you could, for example, produce a 5-phase system with 10 pulses, or 120
if you wanted. You spend a lot on transformers, though.
What does that do for current, anyway? Current through each phase is
essentially a parabolic pulse. All those added up, in the ratios from which
they are generated, should distribute to a fairly constant current,
shouldn't they? Well, the sum of (three phase) currents is always zero, but
the sum of magnitudes isn't: that must oscillate at the 6th harmonic. So it
should be that, in the same way as a choke input filter causes relatively
more current draw on the flanks of the sine wave than overall, this
arrangement also causes more current draw on the flanks, resulting in an
inversely phased 6th harmonic. The curious part is, this nonlinear
conclusion was based on the linear construction of vectors: of course the
diodes, being nonlinear elements, are the reason, but the voltages don't
seem like they should do that.
MooseFET
> On a sunny day (Mon, 4 Jan 2010 06:26:08 -0800 (PST)) it happened MooseFET
> <2562a20f-e214-4701-8f38-50366424a...@a15g2000yqm.googlegroups.com>:
power,
you needed more diodes and a way to share the current so doing this
didn't
add parts.
MooseFET
> "MooseFET" <kensm...@rahul.net> wrote in message
When the number of poles becomes infinite, the harmonics all drop to
zero.
Beyond the infinite number, there is no further improvement.
I hope this helps.
Tim Williams
> When the number of poles becomes infinite, the harmonics all drop to
> zero.
> Beyond the infinite number, there is no further improvement.
> I hope this helps.
How can there ever not be harmonics, either voltage or current, input or
output, when transforming three phase to DC? I think a simple energy budget
shows this is necessary.
Ignoring the three phase source, if you start with n equal voltage, equally
spaced phases, you will get harmonics of 2n and higher, with a current pulse
roughly 1/n of the waveform per phase.
Paul Keinanen
<pNaonSt...@yahoo.com> wrote:
>For much higher power 3 phase rectifiers are used.
>That leaves only a small ripple.
>I am not sure if you need PFC in such a case.
Some issues regarding 3 phase rectifier PFC are discussed in
http://scholar.lib.vt.edu/theses/available/etd-08142002-075617/unrestricted/Barbosa_ETD.pdf
It also contains a long list of references, which might be useful when
doing Google searches.
Jan Panteltje
<kens...@rahul.net> wrote in
<b4f80fb0-b390-4a51...@s31g2000yqs.googlegroups.com>:
>On Jan 4, 7:35�am, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:
>> On a sunny day (Mon, 4 Jan 2010 06:26:08 -0800 (PST)) it happened MooseFE=
>T
>> <kensm...@rahul.net> wrote in
>> <2562a20f-e214-4701-8f38-50366424a...@a15g2000yqm.googlegroups.com>:
>>
>>
>>
>> >On Jan 4, 4:29�am, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:
>> >> On a sunny day (Mon, 04 Jan 2010 07:53:30 +0200) it happened Paul Kein=
>ane=
>> >n
>> >> <keina...@sci.fi> wrote in <q4v2k5hqkr88dmmja3fssrc7o7cdrnp...@4ax.com=
>>:
>>
>> >> >On Tue, 29 Dec 2009 13:44:36 GMT, Jan Panteltje
>> >> ><pNaonStpealm...@yahoo.com> wrote:
>>
>> >> >>On a sunny day (Tue, 29 Dec 2009 07:17:31 -0600) it happened "Tim Wi=
>lli=
>> >ams"
>> >> >><tmoran...@charter.net> wrote in <Yhn_m.18015$wC3.5...@newsfe07.iad>=
>:
>>
>> >> >>>PFC is a flyback thing. �But flybacks suck over 100W, where forwa=
>rd =
>> >looks
>> >> >>>better. �But forward sucks over wide duty cycle ranges. �What d=
>o t=
>> >hey do,
>> >> >>>just bigger flybacks? �Nothing at all?
>>
>> >> >>>Tim
>>
>> >> >>>--
>> >> >>>Deep Friar: a very philosophical monk.
>> >> >>>Website:http://webpages.charter.net/dawill/tmoranwms
>>
>> >> >>For much higher power 3 phase rectifiers are used.
>> >> >>That leaves only a small ripple.
>> >> >>I am not sure if you need PFC in such a case.
>>
>> >> >The ordinary 3 phase 6 pulse rectifier is a quite nasty polluter of
>> >> >the mains.
>>
>> >> >To reduce the harmonics, 12 pulse rectifiers have been used, with one
>> >> >set of rectifiers connected to the wye windings and the other set fro=
>m
>> >> >separate delta windings. For high power systems, you still are going
>> >> >to need a medium/low voltage transformer on site, so it is not a big
>> >> >deal having separate wye and delta secondary windings on that
>> >> >transformer.
>>
>> >> >If you want to get away with the heavy 50 Hz transformer, there seems
>> >> >to be various more or less patented 3 phase systems using flyback etc=
>.
>> >> >systems to reduce the PFC, but these seems to be hugely complex and
>> >> >have special floating requirements for the DC side.
>>
>> >> >If floating output or voltages other than those obtainable by simple
>> >> >rectifiers are required, it might be easier to simply get three singl=
>e
>> >> >phase SMPS with PFC at the input and connect the DC outputs in
>> >> >parallel.
>>
>> >> >If the input voltage ratings permit, instead of wye, connect the
>> >> >inputs into delta to avoid any mains neutral polluting and also allow
>> >> >higher voltage and hence higher power (1.7x) for a specific
>> >> >semiconductor amperage.
>>
>> >> Yes, the ones I have dealt with also had a huge heavy inductor beteen =
>the=
>> > rectifiers and the filtercaps.
>> >> � � � � � � � � � � � � � � � � �L
>> >> � � � � � � � � � � � � � � � ====
>==
>> >=====
>> >> � � �-------------------------^^^^^^^^^---------------- +
>> >> � � | � � � | � � � | � � � � � � � � =
>�=
>> > � � � � � |
>> >> � �--- � � --- � � --- � � � � � � � � �=
> =
>> >� � � � �|
>> >> � �/ \ � � / \ � � / \ � � � � � � � � �=
> =
>> >� � � � �|
>> >> � �--- � � --- � � --- � � � � � � � � �=
> =
>> >� � � � �|
>> >> � � | � � � | � � � | � � � � � � � � =
>�=
>> > � � � � � |
>> >> --- | � � � | � � � | � � � � � � � � � =
>�=
>> > � � � � |
>> >> � � | � � � | � � � | � � � � � � � � =
>�=
>> > � � � � �===
>> >> --- ) ------| � � � |
>> >> � � | � � � | � � � | � � � � � � � � =
>�=
>> > � � � � �--- C
>> >> --- ) ----- ) ----- | � � � � � � � � � � � � =
>�=
>> > � |
>> >> � � | � � � | � � � | � � � � � � � � =
>�=
>> > � � � � � |
>> >> � �--- � � --- � � --- � � � � � � � � �=
> =
>> >� � � � �|
>> >> � �/ \ � � / \ � � / \ � � � � � � � � �=
> =
>> >� � � � �|
>> >> � �--- � � --- � � --- � � � � � � � � �=
> =
>> >� � � � �|
>> >> � � | � � � | � � � | � � � � � � � � =
>�=
>> > � � � � � |
>> >> � � �-------------------------------------------------- -
>> >> The inductor smoothes the main current, and reduces capacitor ripple c=
mmm I dunno,
designed something for the army that a had selenium rectifier in it..
Jan Panteltje
<kein...@sci.fi> wrote in <bt06k5ta0ku0ma6t6...@4ax.com>:
>On Tue, 29 Dec 2009 13:44:36 GMT, Jan Panteltje
><pNaonSt...@yahoo.com> wrote:
>
>>For much higher power 3 phase rectifiers are used.
>>That leaves only a small ripple.
>>I am not sure if you need PFC in such a case.
>
>Some issues regarding 3 phase rectifier PFC are discussed in
>http://scholar.lib.vt.edu/theses/available/etd-08142002-075617/unrestricted/Barbosa_ETD.pdf
I am impressed, felt back at school for a while.
A rather complete design guide!
>It also contains a long list of references, which might be useful when
>doing Google searches.
After reading 240 or so pages...
My head is full :-)
MooseFET
> "MooseFET" <kensm...@rahul.net> wrote in message
>
> news:415e4301-e21b-45c5...@v25g2000yqk.googlegroups.com...
>
> > When the number of poles becomes infinite, the harmonics all drop to
> > zero.
> > Beyond the infinite number, there is no further improvement.
> > I hope this helps.
>
> How can there ever not be harmonics, either voltage or current, input or
> output, when transforming three phase to DC? I think a simple energy budget
> shows this is necessary.
>
> Ignoring the three phase source, if you start with n equal voltage, equally
> spaced phases, you will get harmonics of 2n and higher, with a current pulse
> roughly 1/n of the waveform per phase.
I think you missed that the source is 3 phase power and we are
constructing
more phases with the transformers. If so the rest won't be needed as
you
will already see it.
Imagine that you have a synchronous motor running on 3 phase. The 3
phase power
makes a rotating magnetic field that is of constant strength.
Now imagine that the motor is moving an infinitely fine commutator
under some
brushes such that the contacts are always at the voltage peaks. This
is the
infinite number of poles case.
Paul Keinanen
<tmor...@charter.net> wrote:
>PFC is a flyback thing. But flybacks suck over 100W, where forward looks
>better. But forward sucks over wide duty cycle ranges. What do they do,
>just bigger flybacks? Nothing at all?
Digging deeper into my old archives, the ON Semi PFC Handbook
http://www.onsemi.com/pub_link/Collateral/HBD853-D.PDF might also be
useful for single phase applications up to 300 W.
krw
<pNaonSt...@yahoo.com> wrote:
>On a sunny day (Mon, 4 Jan 2010 18:19:15 -0800 (PST)) it happened MooseFET
><kens...@rahul.net> wrote in
><b4f80fb0-b390-4a51...@s31g2000yqs.googlegroups.com>:
<snip>
>>> An interesting solution, never seen that before, maybe I am too old:-)
>>... Or maybe too young. Back when rectifiers couldn't handle the
>>power,
>>you needed more diodes and a way to share the current so doing this
>>didn't
>>add parts.
>
>mmm I dunno,
>designed something for the army that a had selenium rectifier in it..
I love the smell of burning selenium in the morning.
JosephKK
>On Sun, 03 Jan 2010 11:51:44 -0800, JosephKK wrote:
>
>> I am playing around with modeling 3-phase rectifiers. I think PFC
>> would be a real good thing for 3-phase rectifiers. May be more than
>> a tad interesting to implement though.
>
>Interesting to do if you need to implement synchronous regeneration back
>into the supply from a big variable frequency drive.
>
>
>Following on from your posted simulations, I did this, it's a simplified
>3 phase, 100 amp PSU circuit from a VFD. Regeneration circuitry omitted.
>Power factor varies from 0.26 at no load to 0.94 at full load.
>
>Plot definition file and log file included.
>
>File 3phrect.asc
>
>
>Version 4
>SHEET 1 1652 864
>WIRE 192 -384 64 -384
>WIRE 288 -384 192 -384
>WIRE 560 -384 288 -384
>WIRE 624 -384 560 -384
>WIRE 944 -384 624 -384
>WIRE 64 -288 64 -384
>WIRE 192 -288 192 -384
>WIRE 288 -288 288 -384
>WIRE -192 -64 -688 -64
>WIRE 288 -64 288 -224
>WIRE 288 -64 -112 -64
>WIRE -688 -48 -688 -64
>WIRE 624 -16 624 -384
>WIRE 752 -16 624 -16
>WIRE -688 32 -816 32
>WIRE 624 32 624 -16
>WIRE 752 32 752 -16
>WIRE 944 32 944 -384
>WIRE -176 112 -688 112
>WIRE 192 112 192 -224
>WIRE 192 112 -96 112
>WIRE -688 144 -688 112
>WIRE 624 160 624 96
>WIRE 752 160 752 112
>WIRE 752 160 624 160
>WIRE -816 256 -816 32
>WIRE -688 256 -688 224
>WIRE -688 256 -816 256
>WIRE -192 288 -688 288
>WIRE 64 288 64 -224
>WIRE 64 288 -112 288
>WIRE -688 368 -688 288
>WIRE 64 368 64 288
>WIRE 192 368 192 112
>WIRE 288 368 288 -64
>WIRE -816 496 -816 256
>WIRE -752 496 -816 496
>WIRE -688 496 -688 448
>WIRE -688 496 -752 496
>WIRE 64 512 64 432
>WIRE 192 512 192 432
>WIRE 192 512 64 512
>WIRE 288 512 288 432
>WIRE 288 512 192 512
>WIRE 544 512 288 512
>WIRE 624 512 624 160
>WIRE 624 512 544 512
>WIRE 944 512 944 112
>WIRE 944 512 624 512
>WIRE -752 544 -752 496
>FLAG 544 512 VLneg
>FLAG 560 -384 VLpos
>FLAG -752 544 0
>SYMBOL diode 48 432 M180
>WINDOW 0 24 72 Left 0
>WINDOW 3 24 0 Left 0
>SYMATTR InstName D1
>SYMATTR Value FWD
>SYMBOL diode 176 432 M180
>WINDOW 0 24 72 Left 0
>WINDOW 3 24 0 Left 0
>SYMATTR InstName D2
>SYMATTR Value FWD
>SYMBOL diode 272 432 M180
>WINDOW 0 24 72 Left 0
>WINDOW 3 24 0 Left 0
>SYMATTR InstName D3
>SYMATTR Value FWD
>SYMBOL diode 48 -224 M180
>WINDOW 0 24 72 Left 0
>WINDOW 3 24 0 Left 0
>SYMATTR InstName D4
>SYMATTR Value FWD
>SYMBOL diode 176 -224 M180
>WINDOW 0 24 72 Left 0
>WINDOW 3 24 0 Left 0
>SYMATTR InstName D5
>SYMATTR Value FWD
>SYMBOL diode 272 -224 M180
>WINDOW 0 24 72 Left 0
>WINDOW 3 24 0 Left 0
>SYMATTR InstName D6
>SYMATTR Value FWD
>SYMBOL ind2 -96 304 M270
>WINDOW 0 32 56 VTop 0
>WINDOW 3 5 56 VBottom 0
>SYMATTR InstName L9
>SYMATTR Value 220u
>SYMATTR Type ind
>SYMBOL ind2 -80 128 M270
>WINDOW 0 32 56 VTop 0
>WINDOW 3 5 56 VBottom 0
>SYMATTR InstName L10
>SYMATTR Value 220u
>SYMATTR Type ind
>SYMBOL ind2 -96 -48 M270
>WINDOW 0 32 56 VTop 0
>WINDOW 3 5 56 VBottom 0
>SYMATTR InstName L11
>SYMATTR Value 220u
>SYMATTR Type ind
>SYMBOL cap 608 32 R0
>SYMATTR InstName C1
>SYMATTR Value 5600u
>SYMATTR SpiceLine V=400 Rser=.5
>SYMBOL current 944 32 R0
>WINDOW 123 0 0 Left 0
>WINDOW 39 24 116 Left 0
>SYMATTR SpiceLine load
>SYMATTR InstName I1
>SYMATTR Value 0
>SYMBOL voltage -688 48 R180
>WINDOW 123 0 0 Left 0
>WINDOW 39 24 -12 Left 0
>SYMATTR SpiceLine Rser=.1
>SYMATTR InstName V1
>SYMATTR Value SINE(0 163.293 60 0 0 0)
>SYMBOL voltage -688 240 R180
>WINDOW 123 0 0 Left 0
>WINDOW 39 24 76 Left 0
>SYMATTR SpiceLine Rser=.1
>SYMATTR InstName V2
>SYMATTR Value SINE(0 163.293 60 0 0 120)
>SYMBOL voltage -688 464 R180
>WINDOW 123 0 0 Left 0
>WINDOW 39 24 76 Left 0
>SYMATTR SpiceLine Rser=.1
>SYMATTR InstName V3
>SYMATTR Value SINE(0 163.293 60 0 0 240)
>SYMBOL res 736 16 R0
>SYMATTR InstName R1
>SYMATTR Value 5.6k
>TEXT 416 24 Left 0 !.ic v(VLpos) 140\n.ic v(VLneg) -140 \n *precharge
>TEXT -680 -344 Left 0 !.model FWD D Ron=10m Roff=100e6 Vfwd=0.35 Vrev=600
>TEXT -512 536 Left 0 !.tran 0 1 0
>TEXT -512 584 Left 0 !.meas tran TP avg(V(n001)*I(V1)) *True power
>TEXT -512 640 Left 0 !.meas tran VRMS rms(V(n001))
>TEXT -512 688 Left 0 !.meas tran IRMS rms(I(V1))
>TEXT -512 744 Left 0 !.meas tran AP avg(VRMS*IRMS) *Apparent power
>TEXT -512 800 Left 0 !.meas tran PF param TP/AP *Power factor
>TEXT -616 0 Left 0 ;200V between phases
>TEXT 768 192 Left 0 !.step I1 0 100 10
>TEXT -232 -144 Left 0 !k1 L9 L10 L11 0.5
>TEXT 696 576 Left 0 !.meas tran VL avg(v(VLpos)-v(VLneg))\n.meas tran Pout param VL*I(I1)
>TEXT -200 -184 Left 0 ;Line reactor
>
>
>File 3phrect.plt
>
>[Transient Analysis]
>{
> Npanes: 3
> Active Pane: 2
> {
> traces: 1 {34603010,0,"I(V1)"}
> X: (' ',1,0,0.1,1)
> Y[0]: (' ',0,-120,20,120)
> Y[1]: ('_',0,1e+308,0,-1e+308)
> Amps: (' ',0,0,0,-120,20,120)
> Log: 0 0 0
> GridStyle: 1
> },
> {
> traces: 1 {524291,0,"V(n001)"}
> X: (' ',1,0,0.1,1)
> Y[0]: (' ',0,-180,30,180)
> Y[1]: ('_',0,1e+308,0,-1e+308)
> Volts: (' ',0,0,0,-180,30,180)
> Log: 0 0 0
> GridStyle: 1
> },
> {
> traces: 1 {524292,0,"V(VLpos,VLneg)"}
> X: (' ',1,0,0.1,1)
> Y[0]: (' ',0,225,5,280)
> Y[1]: ('_',0,1e+308,0,-1e+308)
> Volts: (' ',0,0,0,225,5,280)
> Log: 0 0 0
> GridStyle: 1
> }
>}
>
>
>Log file from a run:
>
>Circuit: * H:\Spice\test.asc
>
>.step i1=0
>Direct Newton iteration for .op point succeeded.
>.step i1=10
>.step i1=20
>.step i1=30
>.step i1=40
>.step i1=50
>.step i1=60
>.step i1=70
>.step i1=80
>.step i1=90
>.step i1=100
>
>
>Measurement: tp
> step AVG(v(n001)*i(v1)) FROM TO
> 1 4.92903 0 1
> 2 870.501 0 1
> 3 1719.76 0 1
> 4 2568.47 0 1
> 5 3406.9 0 1
> 6 4215.87 0 1
> 7 5002.64 0 1
> 8 5809.35 0 1
> 9 6569.61 0 1
> 10 7357.99 0 1
> 11 8134.66 0 1
>
>Measurement: vrms
> step RMS(v(n001)) FROM TO
> 1 114.699 0 1
> 2 114.415 0 1
> 3 113.542 0 1
> 4 112.69 0 1
> 5 111.896 0 1
> 6 111.095 0 1
> 7 110.262 0 1
> 8 109.522 0 1
> 9 108.701 0 1
> 10 107.999 0 1
> 11 107.301 0 1
>
>Measurement: irms
> step RMS(i(v1)) FROM TO
> 1 0.165922 0 1
> 2 10.1219 0 1
> 3 18.3089 0 1
> 4 25.879 0 1
> 5 33.501 0 1
> 6 41.1342 0 1
> 7 48.7225 0 1
> 8 56.68 0 1
> 9 64.3137 0 1
> 10 72.3274 0 1
> 11 80.387 0 1
>
>Measurement: ap
> step AVG(vrms*irms) FROM TO
> 1 19.0311 0 1
> 2 1158.09 0 1
> 3 2078.83 0 1
> 4 2916.3 0 1
> 5 3748.64 0 1
> 6 4569.8 0 1
> 7 5372.22 0 1
> 8 6207.71 0 1
> 9 6990.94 0 1
> 10 7811.25 0 1
> 11 8625.57 0 1
>
>Measurement: pf
> step tp/ap
> 1 0.258999
> 2 0.751669
> 3 0.827272
> 4 0.880729
> 5 0.908837
> 6 0.92255
> 7 0.931206
> 8 0.935827
> 9 0.939733
> 10 0.941973
> 11 0.943087
>
>Measurement: vl
> step AVG(v(vlpos)-v(vlneg)) FROM TO
> 1 280.846 0 1
> 2 269.649 0 1
> 3 264.674 0 1
> 4 261.622 0 1
> 5 259.052 0 1
> 6 256.417 0 1
> 7 253.744 0 1
> 8 251.29 0 1
> 9 248.669 0 1
> 10 246.405 0 1
> 11 244.15 0 1
>
>Measurement: pout
> step vl*i(i1)
> 1 0
> 2 2696.49
> 3 5293.48
> 4 7848.67
> 5 10362.1
> 6 12820.9
> 7 15224.6
> 8 17590.3
> 9 19893.5
> 10 22176.5
> 11 24415
>
>
>Date: Sat Jan 16 05:28:55 2010
>Total elapsed time: 21.350 seconds.
>
>tnom = 27
>temp = 27
>method = modified trap
>totiter = 34546
>traniter = 34542
>tranpoints = 15714
>accept = 10511
>rejected = 5203
>matrix size = 11
>fillins = 12
>solver = Normal
>Matrix Compiler1: off
>Matrix Compiler2: off
Thanks Fred. I am learning some stuff about spice from this.
It seems the power factor is not so bad as the harmonics.
JosephKK
>On Tue, 19 Jan 2010 04:26:37 -0800, JosephKK wrote:
>
>> Thanks Fred. I am learning some stuff about spice from this. It seems the
>> power factor is not so bad as the harmonics.
>
>The way true and apparent power were calculated should include the effect
>of harmonics.
While is most certainly does include the power in the harmonics, it does not
calculate the spectral power of each of the various harmonics. I am
interested in the harmonic power by harmonic number.
MooseFET
It is often better to start off with knowing the real power.
Stripping that out
of the waveform makes the wave form you need to process much easier to
deal with.
Only if the FFT in spice works on exactly an integer number of cycles
does it
make the FFT into a single spike. The tail of the skirt on the
fundamental shifts
the other harmonics up.
JosephKK
I studied the impacts of various windowing schemes some 25 years ago.