Distortion rather than displacement

[fkelly]

Is there a PF to consider in CFL?
Distortion rather than displacement.

This was a response to a different post on considering PF in CFL use. Could somebody explain this to me?
I understand that most CFL's have a PF of about .65. I think in my case that is not charged to me by the power company, however, what would happen on a solar / battery / inverter system? Would I use more power than the rated watts of the bulb or would that "unused" (PF) power go back into the system?

 

[glene77is]

Fkelly,

The CFL should have a small switcher supply inside.
It puts out a lot of hash, which has high harmonic content.
So, the answer to your question, in general, is yes.

I have read a 'green' article considering the consequences
of "everybody in the world" using CFL's, and how the power grid would suffer.
PF growing by leaps and bounds. Seems far fetched.
Not everybody will use CFL's.
I certainly prefer my candle, with it's PF = 1.

Welcome to the Forums!

 

[winnie]

Distortion power factor causes similar losses to displacement power factor. The supply system suffers the losses associated with the higher RMS current flow, but only delivers the real power to the load. For an inverter fed system, this will manifest as extra heating in the transistors, and possible output voltage distortion. Apart from these increased losses, the power that the system needs to supply is the real power consumed by the CFL.

-Jon

 

[Besoeker]

Is there a PF to consider in CFL?
Distortion rather than displacement.

This was a response to a different post on considering PF in CFL use. Could somebody explain this to me?

Well, I suppose it was a comment posted by me so I'll try to explain.
A CFL ballast has an input bridge rectifier with capacitor smoothing on the DC side. As a result, the input current is non-sinusoidal. The peaks are higher and the conduction period shorter. This results in higher RMS current being drawn from the supply for the same useful power than would be required if you had a pure sinewave current.

If you define power factor as W/VA, then the distorted current means that the power factor is less than 1.0.

This is different to say, a motor, where the current may be a perfect sinewave but it lags behind the voltage i.e there is a displacement between the two resulting in lagging power factor.

A significant difference between the two is that you can correct lagging displacement with power factor correction capacitors. That doesn't work with distortion PF.

 

[fkelly]

OK, my head hurts now!
Thanks for the responses. I think I am understanding the basic concept. The bottom line seems to be, from a practical standpoint (i.e., being my own "power company"), that I will have some minor loss associated with the higher current flow but no more 'actual use' than the rated wattage of the bulbs.
On a large scale, I guess this could be a big problem but on a small scale shouldn't make much difference.

 

[weressl]

Well, I suppose it was a comment posted by me so I'll try to explain.
A CFL ballast has an input bridge rectifier with capacitor smoothing on the DC side. As a result, the input current is non-sinusoidal. The peaks are higher and the conduction period shorter. This results in higher RMS current being drawn from the supply for the same useful power than would be required if you had a pure sinewave current.

If you define power factor as W/VA, then the distorted current means that the power factor is less than 1.0.

This is different to say, a motor, where the current may be a perfect sinewave but it lags behind the voltage i.e there is a displacement between the two resulting in lagging power factor.

A significant difference between the two is that you can correct lagging displacement with power factor correction capacitors. That doesn't work with distortion PF.

• Distortion referst to non-sinusodial voltage or current and has NOTHING to do with power factor.
• Displacement refers to the relationship between current and voltage phase angles and it is refered to power factor and has NOTHING to do with distortion.

Even though they are separate phenomena they often occur simultaneously.

 

[winnie]

Distortion referst to non-sinusodial voltage or current and has NOTHING to do with power factor.

I disagree with your language but not the underlying concept.

I entirely agree with you that distortion and displacement are two different things.

I have seen the same language that Besoeker describes: these two different things called 'displacement power factor' and 'distortion power factor'.

The broadest definition of power factor is:
{real power delivered} / ( {RMS voltage} * {RMS current} )
This same definition clearly encompasses both distortion and displacement.

-Jon

 

[Besoeker]

• Distortion referst to non-sinusodial voltage or current and has NOTHING to do with power factor.
• Displacement refers to the relationship between current and voltage phase angles and it is refered to power factor and has NOTHING to do with distortion.

Even though they are separate phenomena they often occur simultaneously.

Interesting POV there, Laszlo.
I think Winnie has it right.......kW/kVA

A term used to describe how effectively an electric load converts power into work that is useful. Power factor (PF) can be calculated using the equation: PF = active power/rms x current Note: Current distortion and phase displacement are both known to reduce the power factor.www.ebunit.com/terms.html

Power Factor: a measure of the effectiveness with which an electrical device converts volt-amperes to watts; devices with power factors >0.90 are "high power factor" devices.
http://www.sylvania.com/BusinessProducts/Glossary/

The ratio of watts to volt-amperes of an ac electric circuit
http://www.joliettech.com/easa_engineering_handbook-glossary.htm

Watts divided by volt amps, KW divided by KVA. Power factor: leading and lagging of voltage versus current caused by inductive or capacitive loads, and harmonic power factor: from nonlinear current.
www.powertransformer.us/transformerterms.htm

 

[weressl]

I disagree with your language but not the underlying concept.

I entirely agree with you that distortion and displacement are two different things.

I have seen the same language that Besoeker describes: these two different things called 'displacement power factor' and 'distortion power factor'.

The broadest definition of power factor is:
{real power delivered} / ( {RMS voltage} * {RMS current} )
This same definition clearly encompasses both distortion and displacement.

-Jon

Thanks Jon,

Could you elaborate on what was/is the problem with the "language"?

As I tried to express, both phenomena could exist concurrently, but ARE to be handled as two separate issues. 'displacement power factor' is redundant since power factor IS displacement of TWO distinct parameters, namely Voltage and Amperes. Distortion has NO power factor itslef as it describes the quantitive and qualitive change of a SINGLE parameter, either Voltage OR Amperes.

 

[winnie]

Could you elaborate on what was/is the problem with the "language"?

The language issue is simply that we are using the term 'power factor' differently.

You are using the term 'power factor' to specifically mean displacement between the voltage and current in an AC circuit.

I am using the term 'power factor' to mean the ratio of real power delivered to the product of RMS voltage and RMS current. IMHO this is a more general meaning of the term. I believe that this is also an accepted usage, and have seen it in the literature.

If the system and loads are linear, then these two usages are equivalent.

As I tried to express, both phenomena could exist concurrently, but ARE to be handled as two separate issues. 'displacement power factor' is redundant since power factor IS displacement of TWO distinct parameters, namely Voltage and Amperes. Distortion has NO power factor itslef as it describes the quantitive and qualitive change of a SINGLE parameter, either Voltage OR Amperes.

As I said, I entirely agree with you on the underlying physics; displacement of the current waveform relative to the voltage waveform is one thing, distortion of the current waveform is another.

What term do you use to describe the 'thing that is like power factor but is caused by distortion of the current flow'? In other words, if you have a given RMS current and RMS voltage, and take the product, you will have a measure of apparent power. If the real power is different from the apparent power, and the cause of this difference is non-sinusoidal current flow, what do you call the ratio of real to apparent power?

I would call this 'distortion power factor'; what would you call it under your usage?

-Jon

 

[weressl]

The language issue is simply that we are using the term 'power factor' differently.

You are using the term 'power factor' to specifically mean displacement between the voltage and current in an AC circuit.

I am using the term 'power factor' to mean the ratio of real power delivered to the product of RMS voltage and RMS current. IMHO this is a more general meaning of the term. I believe that this is also an accepted usage, and have seen it in the literature.

If the system and loads are linear, then these two usages are equivalent.



As I said, I entirely agree with you on the underlying physics; displacement of the current waveform relative to the voltage waveform is one thing, distortion of the current waveform is another.

What term do you use to describe the 'thing that is like power factor but is caused by distortion of the current flow'? In other words, if you have a given RMS current and RMS voltage, and take the product, you will have a measure of apparent power. If the real power is different from the apparent power, and the cause of this difference is non-sinusoidal current flow, what do you call the ratio of real to apparent power?

I would call this 'distortion power factor'; what would you call it under your usage?

-Jon

I stand corrected, went to school a looooong time ago in a different language. No excuse though.....

IEEE indeed recognizes displacement and distorted as components of the 'total' power factor, although it is clear by the use of the "" around total that it is a forced defintion, not a naturally derived system as the 'original' definition had to be modified when they recognized that distortion also effects the real power. I guess it came about when semi-conductors and power rectifiers entered the arena.

 

[Besoeker]

Edited on the basis that Winnie made the point much more succinctly that I did.

 

[jghrist]

OK, my head hurts now!
Thanks for the responses. I think I am understanding the basic concept. The bottom line seems to be, from a practical standpoint (i.e., being my own "power company"), that I will have some minor loss associated with the higher current flow but no more 'actual use' than the rated wattage of the bulbs.
On a large scale, I guess this could be a big problem but on a small scale shouldn't make much difference.

There is little difference in the real power requirements, but the distorted current may cause problems with the inverter other than real power limitations.

 

[wirenut1980]

The same amount of current distortion will have a greater effect on the voltage (more voltage distortion) fed from a weaker source such as an inverter, than on the stronger utility source.