# Power supply power factor correction and the US

R

#### Raveninghorde

Jan 1, 1970
0
I'm just reviewing a 120W psu spec. In the EU this would require power
factor correction for the input. The spec I have doesn't mention it
but does refer to MIL-STD-461.

I've had a quick search of the pdf for 461F doesn't mention power
factor correction. So does the US care about PFC on power supplies?
Or is it known by another name?

R

Jan 1, 1970
0
R

#### Rich Grise

Jan 1, 1970
0
I've got a copy of the pdf and can't find anything.

But the Americans and British call things by different names and I don't
want to miss something due to not knowing their language

Earth/ground, DJ/tux, fag/cigarette, petrol/gas ...

Power Factor/Power Factor ;-)

But seriously, sometimes you'll see rectangular cans on the power poles;
they tell me these are capacitors to correct for the power factor of
inductive stuff, like refrigerator motors and A/C motors and stuff.

But I've never heard of a requirement for PFC (power factor correction)
on stuff for household use. Industrial, I haven't investigated, but they
do have a lot of inductive loads, but you'd probably work that out with

Hope This Helps!
Rich

S

#### Spehro Pefhany

Jan 1, 1970
0
I'm just reviewing a 120W psu spec. In the EU this would require power
factor correction for the input. The spec I have doesn't mention it
but does refer to MIL-STD-461.

I've had a quick search of the pdf for 461F doesn't mention power
factor correction. So does the US care about PFC on power supplies?
Or is it known by another name?

This might be useful:
http://grouper.ieee.org/groups/harmonic/docs/usccemc9901.pdf

R

#### Raveninghorde

Jan 1, 1970
0
Power Factor/Power Factor ;-)

But seriously, sometimes you'll see rectangular cans on the power poles;
they tell me these are capacitors to correct for the power factor of
inductive stuff, like refrigerator motors and A/C motors and stuff.

But I've never heard of a requirement for PFC (power factor correction)
on stuff for household use. Industrial, I haven't investigated, but they
do have a lot of inductive loads, but you'd probably work that out with

Hope This Helps!
Rich

Over here almost any PSU over 75 Watts (from memory) needs to be unity
power factor. That is sinusoidal current consumption in phase with the
voltage.

http://en.wikipedia.org/wiki/Power_factor#Active_PFC

So for the EU I need a more complex PSU than some other countries.
This project is for Asia but calls up US military standards. The only
place the requirement could be hiding is in 269 pages of the EMI/EMC
spec.

H

#### Holloway,Graham $$UK$$

Jan 1, 1970
0
Raveninghorde said:
I'm just reviewing a 120W psu spec. In the EU this would require power
factor correction for the input. The spec I have doesn't mention it
but does refer to MIL-STD-461.

I've had a quick search of the pdf for 461F doesn't mention power
factor correction. So does the US care about PFC on power supplies?
Or is it known by another name?

Is it a military PSU? If they're quoting MIL STD 461 for EMC, it probably
is. The relevant document for electrical supply quality is then MIL STD
704(F?) by association. It says there is no need for power factor correction
below 500watts. The only noteworthy comment is that you can't use half-wave
rectification. Don't laugh, I know someone who did.

Graham H

R

#### Raveninghorde

Jan 1, 1970
0
Is it a military PSU? If they're quoting MIL STD 461 for EMC, it probably
is. The relevant document for electrical supply quality is then MIL STD
704(F?) by association. It says there is no need for power factor correction
below 500watts. The only noteworthy comment is that you can't use half-wave
rectification. Don't laugh, I know someone who did.

Graham H

Asian military.

And thanks that's the answer I needed. I'll find MIL-STD-704 for
reference.

N

#### Nobody

Jan 1, 1970
0
Over here almost any PSU over 75 Watts (from memory) needs to be unity
power factor.

Nope. There are some constraints upon the power factor, but they're so
lax that you would have trouble violating them if you tried.

J

#### JosephKK

Jan 1, 1970
0

That pretty well says what is what, in the US, for regulation, however
there are some limits for meeting the "energy star" compliance here. I
have also seen industrial loads where the utility required active
power factor / harmonic correction. Otherwise, there are requirements
that are part of equipment purchases and some manufacturer's
associations that are putting out voluntary compliance standards.

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