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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.

The only power supplies to use a power factor correction cap was a
few switching power supplies. It was used after the rectifier and
before the choke though. It was never placed in the AC line. I did
see some series regulated supplies in transceivers that had a cap
across the secondary in a bridge rectifier supply, but it was for a
filter. Their values ran from 0.001 uF to 0.01 uF. Nothing of any
size.

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.

The links below go to several webpages and a couple of PDFs on the
subject.








power_optimizing_singlestage_power/









Best,

Will

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.
At that time I wasn't the engineer doing this, but I was around it enough.
There's formulas for balancing the act.. How much capacitance to add etc
depending on the current PF and how many HP of motor load...

PFC is used because Electric motors exhibit a HELACIOUS Inductive load on
the mains while converting to work.

In an inductive circuit the voltage leads the current by 90 degrees. This
inductive load tosses the power company out of SYNC. They are busy trying
to match things up at the power plant.

They generate 3 phases of power. The load on the generators' phases needs
to be balanced. A way off power factor screws the system. If everybody
allowed the PF to get away from them you'd have a real mess... The idea is
to make the current flow run in sync with the AC sign wave.

Commercial power is sold with a base rate for so many KWH, the demand (how
fast you use it) and a premium penalty for power factor varying from 100%.

I worked with an injection molding plastics factory. The big injection
machines had very large motors and that place's PF was way the heck out
there.

Instead of correcting the building.. We installed smaller correction banks
on each machine (about 40 of them at that time) as you can have too many
caps installed and shift the PF the other way.

We generally don't measure PF in residential as there isn't a huge supply of
big motors throwing things off. Some areas with demand limiting of energy
conservation do-do demand metering and control. None I've seen here do PF
measuring at the residential level.

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.

BOB DD

When I worked as an industrial electrician for several years after I
moved up here, we had them several places within the plant. However,
they were all on circuits that had several motors running. The push-
in jig at ACF Industries has about 16 hydraulic units on it, each
with about a 5 HP, 3 phase motor. That was where one large cap was
mounted overhead. I used to have to check it once a month on P.M. as
it had PCB's in the oil. We had to check it for leaks. There was a
few others, one in the power house where some M-G units were that
made the DC for some overhead cranes. That's about the only ones I've
been around besides some that were in plants where I was working in
engineering, and didn't have to fool with them anymore. I've never
seen any used with a transformers secondary. The reactance created by
motors can drop the power factor down a good bit. They were only
recommended to be used at a PF of under 0.80. Then, you spec them by
kVAr instead of capacitance. You find the recatance of the circuit in
question to calculate them, but they are sized and bought really by
specing a kVAr rating. What the kVAr rating is compared to
capacitance, I don't know. One might look into a catalog for them to
see. Then you also have to worry about harmonics too. They make these
up as PF corrector-harmonic filters also. They attach to each of the
three line legs of the 3 phase circuit. Some use a power monitor to
kick in and out the bank of caps when needed.

I think it would end up costing more, and placing more of a load on a
transformer by connection a cap across the secondary. It would be
similar to connecting a resistance of some amount in parallel with
the winding acting like a leak raising the current.

Best,

Will



--- 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.

At that time I wasn't the engineer doing this, but I was around it

enough.

There's formulas for balancing the act.. How much capacitance to

add etc

depending on the current PF and how many HP of motor load...

PFC is used because Electric motors exhibit a HELACIOUS Inductive

load on

the mains while converting to work.

In an inductive circuit the voltage leads the current by 90

degrees. This

inductive load tosses the power company out of SYNC. They are busy

trying

to match things up at the power plant.

They generate 3 phases of power. The load on the generators'

phases needs

to be balanced. A way off power factor screws the system. If

everybody

allowed the PF to get away from them you'd have a real mess... The

idea is

to make the current flow run in sync with the AC sign wave.

Commercial power is sold with a base rate for so many KWH, the

demand (how

fast you use it) and a premium penalty for power factor varying

from 100%.

I worked with an injection molding plastics factory. The big

injection

machines had very large motors and that place's PF was way the heck

out

there.

Instead of correcting the building.. We installed smaller

correction banks

on each machine (about 40 of them at that time) as you can have

too many

caps installed and shift the PF the other way.

We generally don't measure PF in residential as there isn't a huge

supply of

big motors throwing things off. Some areas with demand limiting of

energy

conservation do-do demand metering and control. None I've seen

here do PF

measuring at the residential level.

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.

BOB DD

-----Original Message-----
From: ham_amplifiers@...

[mailto:ham_amplifiers@...]

On Behalf Of craxd
Sent: Friday, November 17, 2006 6:22 PM
To: ham_amplifiers@...
Subject: [ham_amplifiers] Power factor correction for transformers

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.

The only power supplies to use a power factor correction cap was a
few switching power supplies. It was used after the rectifier and
before the choke though. It was never placed in the AC line. I did
see some series regulated supplies in transceivers that had a cap
across the secondary in a bridge rectifier supply, but it was for a
filter. Their values ran from 0.001 uF to 0.01 uF. Nothing of any
size.

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.

The links below go to several webpages and a couple of PDFs on the
subject.

switch_mode_power_supplies/

power_optimizing_singlestage_power/









Best,

Will





Yahoo! Groups Links

--- 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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