Power Factor [RE-wrenches]

[Hugh Piggott]

<x-flowed>
As I understand it, Power factor is the ratio between the actual 
power delivered to the load and the apparent power which is the 
product of (rms) volts and amps.

At 1:20 pm -0600 20/6/02, Ray Walters wrote:
>  My understanding of PF is that it is representative of the lag 
>between the peak of the voltage wave with respect to the current 
>wave. If both current and voltage peak at the same time, PF = 1.

That is true if the current is sinusoidal.  Power factor is then 
cos(phase angle between current and voltage).  Your explanation fits 
this case, but there are other cases where apparent power or 'VA' is 
greater than real power (watts).

If the current is not sinusoidal (e.g. where it consists of pulses 
with high peaks), then you can have a very high rms current without 
achieving a high power output, so the power factor can be poor for 
this reason rather than due to a leading or lagging phase angle.

For example pwm devices will have poor power factor when using narrow 
pulses.  Brief high peaks of current will have much higher rms value 
than smooth current.

The usual comment about being ripped to shreds apply here.  Enlighten 
me further.
-- 
Hugh

http://www.scoraigwind.co.uk/

- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://www.topica.com/lists/RE-wrenches/

List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com

==^================================================================
This email was sent to: michael.welch at homepower.com

EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9
Or send an email to: RE-wrenches-unsubscribe at topica.com

T O P I C A -- Register now to manage your mail!
http://www.topica.com/partner/tag02/register
==^================================================================


</x-flowed>