obviously this guy is a liar too, and was paid to lie to everyone about his
meanwhile, I continue to worship at the feet of all you smart guys on this
newsgroup who have never done any experimentation, but still know
conclusively that the science and the technology are fake.
thanks for all your good advice.
think I'll go walk to the end of the flat earth and watch the universe
revolve around me.
Gotta love that scientific process! Hahaha. No controls. No metering.
Wow, this guy needs to work in the medical field. He could put MRIs out of
If this is the best you have, you are in a sad state.
Charles Perry P.E.
There's nothing wrong with the well known science and technology involved
with capacitances for power factor correction.
What is wrong are some of your claims and some of your version of the
science (part of which is merely misleading and part of which is simply
I could detail a number of points from your own literature but I have dealt
with these before as have others who have shown far greater technical
competence, knowledge of both practice and theory, (and honesty) than you
Don Kelly firstname.lastname@example.org
remove the X to answer
Oddly enough I am in the midst of a situation that bears some resemblance to
the demonstration, albeit a much larger scale..
The load is about 60 kW with a PF of .991 (measured). It is 180 amps 3
phase. Everything is fine on mains power but when switched to generator
power harmonic distortion of the AC rises to 10%. The equipment (load) DC
power supply voltage drops 5 to 10%.
AC generator line voltage shows the same as line voltage with both standard
and true RMS DVMs.
Here's the resemblance: although stuff seems to be working there is 5 to 10%
less power transfer to a slightly reactive load.
The generator tests fine on an 80 kW non-inductive load. Rating is 130 kW.
A few comments:
Gensets can handle only a relatively small amount of capacitive
loading (leading pf), they go unstable. Rough rule of thumb,
capacitive kVAR equal to 10% of kVA rating is the limit, IIRC. Could
be more or less.
Gensets can handle only a moderate amount of harmonic current load.
The genset mfr can probably advise on capacitive current limitations
and - somewhat - on harmonic current limitations.
Maybe the impedance of the genset is an issue. Trying to draw
significant currents - at higher frequencies (5th, 7th, 11th, 13th) -
through the synchronous (inductive) reactance of the genset may cause
a fair voltage drop or flat topping of the voltage waveform and a
reduction of RMS voltage.
You say the power factor is 0.991, do we know the displacement power
factor, distortion power factor, and total power factor? Is the
displacement pf leading or lagging? Do we have an idea of the
harmonic spectra - mostly 5th, 7th, 11th, 13th? no dc? no even
harmonics? no triplens? Nicely balanced between phases? These
questions about harmonic spectra are just a bit of a fishing
I have some reservations as to the benefits of adding more resistive
load. Mathematically this sounds nice because you are bringing the pf
closer to unity and reducing the % harmonic current. However you are
not reducing the actual number of amps of capacitive (or inductive as
the case may be) current nor the actual number of amps of harmonic
current and I suspect the actual number of amps of current is what is
most critical in each case. It is worth a shot though, a genset
company can bring around some resistive test loads easily enough, if
you have a splitter, breaker, or some place to connect them to while
the plant is still running.
If you put harmonic line filters on the output of the genset, be
careful. Simple filters are normally quite capacitive and can be bad
news for a genset as the genset does not like a capacitive load. Some
filters come on in stages, some are active harmonic cancellation, I
suspect these would be better suited to application with a genset.
The UPS guys learned this the hard way. Gensets had to be drastically
oversized to handle UPS because the gensets didn't like the harmonics
that UPS drew. So the UPS guys put filters on the front ends. That
cleared up the harmonics but now the gensets didn't like the
capacitive load that the UPS filter presented.
First thing I would try is to get a generator mfr / service guy to
come down and take a look for free, or for a bit of money if he's
bringing test banks too. Next thing would be to check out costs to
get filtering supplied and installed ($20-40k?). I would look for a
power quality type consultant if one could come down cheap enough that
it is worth the risk of getting non-conclusive results, maybe $5k.
Look for one with tons of experience with gensets, UPS, transformers,
harmonics, and power quality, and with a quality 3 phase power
monitoring / waveform capturing / transient capturing logger like a
Dranetz, BMI, RPM, or whatever.
Isn't 0011, 3? Then I guess the answer would be "no." :)
The buiilding measures .991 inductive. The major load is speced at .94.
additional loads are lighting, obstruction beacons (1,800 W, flashing), 2
cell companies with a/c cooling, building HVAC and 5,400 watts of antenna
5th an 7th, no even
pretty well ballanced... the cell sites are single phase and were measuring
50 to 60 amps on a hot day with thier A/C running. The gen tests were on a
I realize i have incomplete data at this time. It's just a problem i am
facing that seemed to relate to the way the gizmo that made the W-H meter
slow down. Thats assuming the whole test jig wasnt rigged.
No noticable effect, still had 5 to 10% reduction in power supply voltage
and the consiquent reduction in output power.
This location loses power several time a year. It also has had a couple of
mysterious 'brownouts" the power co. can't or won't explain. voltage on all
3 legs drops from a nominal 208 to 190. My equipment just shuts itself down
then. They told me their PF capacitor banks are non switching.
He was there. He pretty much demonstrated the that genset is performing to
'Corporate says: "we have these things running all over the country and
don't have this problem elsewhere"
> I would look for a
With a large 3 phase diode rectifier I could believe a dispalcement
power factor near unity if I had to. This rules out problems due to
leading pf. (Strangely, yesterday as I read '0.991' power factor, and
typed '0.991' power factor, I was thinking '0.911' power factor).
However there ought to be a whole bunch of harmonic current, and a
horrible distortion power factor. Normally that would be my first
suspect. I would expect that a genset supplying a bare (no filters or
harmonic mitigation) 3 phase rectifier might have to be rated between
1.4x and 4x the rectifier rating - these are derating numbers I had
heard from UPS mfrs, maybe 6 years ago, in regards to sizing gensets
that would feed UPS with their rectifying, high harmonic, front ends.
If you have a step up transformer in front of your rectifier, this
should act as a bit of harmonic filtering, like a series choke or
series inductor. Sometimes large rectifiers are fed via TWO
transformers, with some phase shifting (e.g. one Y-D transformer and
one D-D transformer) as this tidily causes a bunch of harmonic
cancellation. I think this would not be the case at your site as this
setup should remove the 5th and 7th harmonics.
If there are similar sites around the country with the same rectifier
and the same genset with the same controller, regulator, alternator,
and excitation, and no voltage problems, then I would have to suspect
a problem with THIS genset. If you know the current distortion you
might be able to ask the genset mfr if the genset ought to be able to
handle it. If the genset people say yes, the genset ought to be able
to handle it, then maybe there is a problem with the unit. If the
genset people say no, this genset can't handle those harmonics, then
maybe they can tell you what exactly the difference is between this
site and other sites where the gensets can handle it? (It's worth
knowing for future installations).
Another possibility is a resonance condition. If there is a
significant capacitor somewhere in the distribution (fed by the
generator) there is a chance that it makes a parallel resonance with
the genset inductive impedance at a critical frequency (e.g. somewhere
around 5th to 7th harmonic or even 11th to 13th). Voltage distortion
would be terrible (as it is seen to be). It is a slim chance and I
don't see anything that looks like a capacitive load in your
description of loads. I would continue to look into the genset first
before investigating this. If you are able to run the convertor on
genset power, with all the breakers to all other equipment open, and
the voltage problems persist, then resonance is very likely not the
Well, is 10% voltage THD and 10% voltage drop 'to spec'? Or did he
show that the genset is operating 'to spec' under linear loads only?
These are rhetoric, and are the same issue as discusse above re:
should this genset be able to handle the current harmonics it is being
Corporate has a point. I would discuss this with the genset people.
Does this genset have a lesser spec, or a lesser controller,
regulator, alternator, or excitation? Round up some detailed specs or
shop drawings for a couple of similar installations (similar loads,
similar load ratings, and similar genset) if you can.
That doesn't make much sense. What you are interested in is an
instantaneous reading of both the harmonic currents and voltage
distortion. That will give you an idea of the source impedance at the
The neutral current is only one problem caused by harmonic currents. The
above is correct, albeit somewhat poorly worded. But high harmonic
currents drawn on the phases can result in voltage distortion.
Particularly if the source has a higher impedance at harmonic
frequencies. This voltage distortion will be seen by every load on the
system and can cause strange load behavior.
The filter vendors will probably have the best ideas about what sorts of
measurements need to be made to specify the correct solution.
Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com
At the time I didn't know what questions to ask. After talking to an
applications engineer today I believe it was 10% voltage distortion.
The applications engineer of a filter vender spoke with me at length. I now
have an assignment to query the generator's aplication engineer about a
I appreciate the thoughtful comments. I was able to study some areas that
are new to me which allowed me to communicate better with the ap eng.
Is there a convertor transformer that steps voltage up from 208V to 7
or 8kV or so? If so the transformer ought to be very much like a
series inductor of a few percent - if the transformer is 5%IZ
impedance then it is somewhat like a series inductor of around 5%. A
little less inductive than a 5% inductor and a little more resistive,
but in the neighborhood.
If an active cancellation filter is deemed to be required, and is
horribly expensive, it may be worth asking the genset people if the
genset can be modified to handle the harmonic current. If it is a
matter of changing the controller it may be 'only' several thousand
By the way, when current harmonic distortion is discussed in
'percentages' (e.g. %THD or "40% current distortion) it is a little
ambiguous as percent current distortion is sometimes measured as
current distortion = (combined total harmonic current of all harmonic
frequencies) / (RMS of total current)
and sometimes as
current distortion = (combined total harmonic current of all harmonic
frequencies) / (RMS of fundamental)
In the first case, a heavily distorted current can show up as, say,
80% harmonic distortion. In the second case the same current waveform
could be way over 100% harmonic distortion. For your waveform at full
load I would expect the discrepancy between the two measurements to be
much less than this and hopefully small enough to not be a concern.
If the utility technician can tell you the amps of harmonic current at
each frequency then that is completely unambiguous.
Two more quick thoughts. It may be that adding a series inductor will
add to the problem. The inductive impedance of the genset (and step
up transformer (if there is one), and cabling) may be contributing to
the poor voltage (low RMS value and heavy distortion) at the rectifier
input. While more inductance may reduce harmonic current draw, I
think it could only do so at an increase of voltage problems. Since
it is the ac voltage peak that 'tops up' the dc capacitor in a
rectifier, the dc voltage would probably be very sensitive to the peak
value of the applied ac voltage. Your ac voltage is probably
'flat-topping', due to the impedances plus a possibly struggling
genset, and causing the low dc voltage. I would mention this to the
filter guy, he should be able to debunk this idea if it is bunk.
Also, you already have the genset people, filter people, and,
somewhat, the utility people involved. You may also want to call up
the vendor of the rectifier equipment. They may be able to say how
much harmonic current the thing is expected to draw, and what voltages
(RMS and distortion-wise) it may be able to tolerate. A four way
teleconference may help get things rolling.
Exactly right. Most nonlinear loads of this type draw nearly constant
harmonic currents. If the voltage source is ideal (zero impedance at the
harmonic frequencies), the system voltage will remain a pure sine wave.
As the source impedance increases, harmonic currents will result in
harmonic voltage drops.
If a blocking filter is placed between the system and the one offending
load to block the currents, other loads may be protected, but the one
producing the currents will see highly distorted voltages. The best
filters offer a combination of a low impedance path for harmonics to
flow (such as a transformer with a tertiary delta winding) plus high
impedance to block the currents from being drawn from a common source
Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com
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