--- In ham_amplifiers@..., "Robert B. Bonner"
<rbonner@...> wrote:
Guys,
My first job out of my undergrad program was with a building
automation (energy) company. We installed PFC caps on buildings
all over the place.
For the Super Big guns that are running 100 AMP primarys with
three phase power supplies doing PFC will just make the power to
the primary smoother and your power company happier. I don't think
it is worth the expense for correction caps. Either way I would
install them on the amplifier not the building.
### On HV supplies with resonant choke filters.... they all have
a better power factor... compared to a simple C input filter.
When you increase the C in a C filter HC supply... the power
factor gets WORSE. Sounds to me like this 90 deg lag is not a
fixed thing... but vary's... depending on power factor itself...
IE: .8 pf vs .9pf vs .98pf
### Since a simple C input filter has a WORSE PF than a resonant
choke filter.... my electrician buddy is suggesting the huge C is
responsible for the worsening pf.... and NOT the XL of either
the pri/sec of the plate xfmr. If that's the case... Dahl is
probably right, he should know. Dahl is telling me on a large C
input filter, that you can't use PF correction caps on the pri
of the plate xfmr. It just makes the PF worse still... and
magnetizing current increases. Since the C filter on the output
side is responsable for the lousy PF on a C input filter... probably
what's needed is a choke.. or XL across the plate xfmr pri.... or
perhaps in series with the plate cfmr pri ??
### Even if it could be done... the load is not constant on the HV
supply... it's nil [except for magnetizing current and bleeder] on
RX.... and vary's on TX from ZSAC... to full bore. Any
compensation would probably have to be relay switched out on RX...
and optimized for an average load on TX... on ssb anyway.
BOB DD
WILL SEZ... I looked through about every book I have on
transformers and power supplies, and never found anything about
using a cap for power factor correction. There's plenty about using
a cap with an AC motor, but nothing about transformers. The
Standard Handbook For Electrical Engineers only show adding them to
motor circuits or circuits feeding motor loads. Nothing under the
transformer section.
### That's what I suspected. I don't see any PFC caps on SW
broadcast TX either... not at 1st glance anyway. None of them are
using C input filters I believe.... might be wrong. With 3 phase
HV... ripple is only 4.8 % b4 any filtering. A simple C input
filter would reduce the ripple to zip. However a resonant
choke would do the same thing.. and have a better power factor at
the same time. For 24/7 operation.. and huge power... any
savings would add up.
WILL SEZ... The only way to cut back on magnetizing current is to
use more iron in the core lowering its flux density. The more iron
for the same amount of turns, the current drops. I researched
magnetizing current in C-core Hipersil (or M-6) transformers some
time back, and seen they had a good bit more magnetizing current
than most EI cores using M-19 steel. The reason being is they run
Hipersil from 15 to 17 kilogauss. M-19 and M-22 are ran from 14 to
10 kilogauss. Over 15 kilogauss in Hipersil, the current really
shoots up. The way to cure this is to have a transformer wound with
the same number of turns, but with a larger core area in either a C-
core or an EI core. One would have to tell the winder to use a
lower flux density of say 12 to 10 kilogauss using a C-core with
Hipersil or M-6 for a low magnetizing current. M-19 for an EI core
may be a better choice if available as it will be a good bit
cheaper. The core loss isn't much greater than M-6 either.
### I'm gonna ask Dahl what kind of hypersil he uses. The 120
lb 10 kva hypersil pole pig I have has 1.9 A of magnetizing
current at all times. The 253 lb Dahl hypersil has only 1.6
A of magnetizing current [it's a 3 A CCS sec = 15.5 kva CCS] I
was expecting a LOT more magnetizing current from the 253 lb
xfmr. [esp since it's double the weight of my pole pig]. The
1.6 x 240v = 384 Va of magnetizing va is small... compared to the
4.5 A int load you can pull off the sec. Still.. that's 384-va
on RX all the time.
### BTW... it's 384 va... whether FWB/caps/bleeder connected...
OR disconnected.. makes no difference.... even when sucking 100
w of bleeder diss. Ditto with pole pig supply.
### Dahl tells me the A-540 core he uses on all the 253 lb'ers is
good for 20 KVA CCS. Once u get a sec over 4 kv... the CCS I
rating drops from 4 A... down to 3 A. At 7.5 kv sec... it's
then down to 2.5 A CCS. My xfmr [due to wire ga on sec] is
rated at 15.5 kva..... however the core itself is good for 20 kva.
later... Jim VE7RF
Best,
Will
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