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.

 

[ackbarthestar]

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.

This has nothing to do with powerfactor but Intefifciofactor . Use a SMP to change the frequency of the localized lamps.

 

[Inteificio]

As I said, i'm not sure it would work.

I am basing my assumption on the fact that the peak power would no longer be exactly at the same point due to the current lag.

As the two peak powers would not longer be in line it would delay the flicker.

The fact that this also would mess with the power factor was a secondary concern, so not really the best thread for it.

Where is my logic failing?

 

[Inteificio]

Soory for my noobness, SMP?

 

[Knobhead]

So what does SMP stand for?

Significant market power
Special Milk Program
State Management Plan
Service Management Platform
Strategic Management Plan
Safety Management Program
Sex, Money, Power
Simple Minded People
See Me, Please
Smoke More Pot
Standard Maintenance Procedure

All recognised international acronyms (there’s about 70 more).

 

[ackbarthestar]

So what does SMP stand for?

Significant market power
Special Milk Program
State Management Plan
Service Management Platform
Strategic Management Plan
Safety Management Program
Sex, Money, Power
Simple Minded People
See Me, Please
Smoke More Pot
Standard Maintenance Procedure

All recognised international acronyms (there’s about 70 more).

- Must be an investment banker !

SMP stands for Switched Mode Power Supply - Very clever device........

Because you can utilize it to change ac to ac , ac to dc, dc to dc and dc to ac at any frequency you like ! - almost a gift of the gods .....

that is those who can see them !

 

[Inteificio]

I assumed that is what you meant, just wanted to make sure.

No room for an SMP in this device, and the costs would be prohibitive.

Had a simple thought last night, just putting a run cap in parallel with the load would have a smoothing effect.

Another thought is the control circuit for this device has a 12v line, not supposed to be for external use, but have 'borrowed' it for testing before. It might be enough to run a few LEDs.

 

[trebor]

actually mate your 0.8 is not far out, the commonly recognised pf limit for lagging current is 0.85, any thing lower than this will be heavily penalised by vectoral summation metering and charges in rkwh units, lagging curreny caused by inductive loads is normally rectified by installing pf correction equipment (capacitor banks for example to reduce the financial costs
As a point of interest in a building with inductive load and poor pf the main tails etc are normally hotter than expected for the visible real load, hope this helps

 

[trebor]

the only time the pf figure is applied is when a circuit is being designed and there is known pf component, lets say a 10kw 400 V motor with a pf of .8 and eff of 1
the load in amp would be caalculate as

P/V / .8 / 1 = I

10000/400/.8/1 = 31.25 amps /3 = 10.41A per phase

 

[The Ranger]

the only time the pf figure is applied is when a circuit is being designed and there is known pf component, lets say a 10kw 400 V motor with a pf of .8 and eff of 1
the load in amp would be caalculate as

P/V / .8 / 1 = I

10000/400/.8/1 = 31.25 amps per phase

should there not be a 1.732 in there as well?

 

[JUD]

should there not be a 1.732 in there as well?

I thought that too. √3 = 1.73

P ÷ (√3 x V) ÷ pf
10000 ÷ (√3 x 400) ÷ 0.8 = 18A per phase

 

[Engineer54]

What you need to remember about PF correction is that your only correcting up to the point the capacitor(s) are connected!!

So if you have a large motor that has a PF of say 0.60 and you apply correction to the terminals of that motor, your only correcting that lagging current in the cable supplying that motor, ...the motor will still be running at 0.60 lagging!!

Capacitor banks used to circumvent penalty charges from the DNO and normally connected just after the main protective device on the supply side of the installation. They Will do nothing to reduce the overall PF of the installation, that will remain the same. Only the DNO's meter and supply cable, will see the effects of the capacitor bank.

 

[nil26]

Power factor is defined as the ratio of the real power, between 0 and 1. It is the value given to a either inductive or capacitive. The capacitive is applied to electric circuits.