power factor correction

[The Ranger]

Well time has come to further my knowledge, now I know I was taught these at college but once i left i realised it was all about thinking from the neck down! So I know the rule of thumb is .8 but how do I apply these into calculations:freak:

 

[Inteificio]

Rule of thumb is related to Zs.

use google to learn what both of those mean.

 

[The Ranger]

I know what Zs is i passed my 2391 years ago
Zs = Ze+R1+R2

 

[Inteificio]

That would be an approximation of ZS.

R1+R2 is a measurement of resistance not impedance.

To be fair I was being a little cheeky, no offence meant. Just a gentle poke in the ribs ;-)

 

[The Ranger]

no offence taken!


the reason for the question is I done most of my 2391-20 this year i was all good till the power factor gets thrown in it throws me been searching google for days to no avail

 

[Inteificio]

I must admit, the reason I went to this thread is that although I can get all the power factor questions easily; the issue for me is I have no idea how to apply them to real life!!!!

I was hoping someone else would explain in this thread =-)

 

[micknew]

Power factor is the value given to a capacitive or inductive load.
Power factor of a resistive load is 1.
Putting it simply it is a number that represents the power output of a load to the power being taken from the supply.

 

[Knobhead]

Have a look at Practical power factor correction : POWER FACTOR I've got plenty of painkillers if you need any posting to you.

 

[Inteificio]

Can I tag a small question on to this?

I have a device with two lights next to each other providing heat to a plate (GU10 50w).

As our mains supply is a bit ****, I was thinking of putting a cap in series with the second light pushing the dips in voltage slightly out of phase with the first lamp.
Am hoping this would average out the flicker a bit as both lights will flicker at different times.

This is another power factor question, but any idea what calc I should be doing to get the cap size?

I do not want to push the pf too far out or the light will start to dim (I think), but in turn want a time delay.

So anyone care to help?

 

[Knobhead]

A halogen lamp is incandescent, PF plays no part in it.

 

[Deleted member 9648]

Can I tag a small question on to this?

I have a device with two lights next to each other providing heat to a plate (GU10 50w).

As our mains supply is a bit ****, I was thinking of putting a cap in series with the second light pushing the dips in voltage slightly out of phase with the first lamp.
Am hoping this would average out the flicker a bit as both lights will flicker at different times.

This is another power factor question, but any idea what calc I should be doing to get the cap size?

I do not want to push the pf too far out or the light will start to dim (I think), but in turn want a time delay.

So anyone care to help?

Wot Tony said...Tungsten lamps are a resistive load,you could only produce a lead/lag effect with discharge lighting....ie fluorescent lamps control gear.

 

[ackbarthestar]

Power factor applies to inductive loads, where coils are used to provide a large back emf to fire up discharge tubes and then used to limit the current flow across the tubes. Motors being inductive also require pf correction.

Since a capacitor provides a leading power factor, it counteracts the laging pf of the coil, to a degree. You don't want a perfect correction since this can create large oscillating currents and voltages across the components, usually an acceptable value would be around 0.93.

Most individual components with coils and capacitors as a rule of thumb provide a basic pf correction of 0.85. This in most cases is suitable for small installations but would require further correction, at the main incomer for large installations

 

[The Ranger]

Power factor applies to inductive loads, where coils are used to provide a large back emf to fire up discharge tubes and then used to limit the current flow across the tubes. Motors being inductive also require pf correction.

Since a capacitor provides a leading power factor, it counteracts the laging pf of the coil, to a degree. You don't want a perfect correction since this can create large oscillating currents and voltages across the components, usually an acceptable value would be around 0.93.

Most individual components with coils and capacitors as a rule of thumb provide a basic pf correction of 0.85. This in most cases is suitable for small installations but would require further correction, at the main incomer for large installations

so how do you put this 0.85 into a cable calc?

 

[ackbarthestar]

so how do you put this 0.85 into a cable calc?

For motors the info is on the nameplate kW=XX and Pf=XX, or kVA=XX and pf=XX or kVA=XX and kW=XX
A simple couple of equations are used:

1/ kVA= kW/pf
2/ I = kVA/V

For lighting the power is usually quoted in Watts so apply the above formula without the 'k'

The important thing is the current in the cable which is the apparent power, not the power consumed by the load.

 

[Inteificio]

I am not trying to correct the power factor of a halogen, I am trying to ruin it.

Adding a cap will put a slight delay in the system. This delay will put the flickers out of phase with each other, 'hopefully' reducing the visibility of it.