Power Factor Explained - The basics what is power factor pf

Summary

في هذا الفيديو، يناقش بول من TheEngineeringMindset.com مفهوم معامل القدرة (Power Factor) بأسلوب مبسط عبر أمثلة تشبيهية، مثل تشبيه الجعة بالرغوة، لتوضيح الفرق بين القدرة الحقيقية والقدرة الظاهرة. يتطرق إلى ما هو معامل القدرة، الفرق بين معامل القدرة الجيد والسيء، ما الذي يسبب انخفاض معامل القدرة، وكيف يمكن تصحيحه باستخدام المكثفات أو المحاثات. كما يوضح كيفية تأثير ذلك على فواتير الكهرباء في المباني السكنية والتجارية، ويشرح أهمية تحسين معامل القدرة لتجنب الرسوم الزائدة وزيادة كفاءة الشبكة الكهربائية.

Takeaways

• ⚡ معامل القدرة هو نسبة القوة الحقيقية إلى القوة الظاهرة في الدوائر الكهربائية ذات التيار المتناوب.
• 🍺 الكيلوواط يمثل القوة الحقيقية (الطاقة المفيدة)، بينما تمثل الـkVAr الطاقة التفاعلية (الرغوة) التي لا يمكن استخدامها ولكن يجب دفع ثمنها.
• 🔢 معادلة معامل القدرة: PF = KW / kVA.
• 🏠 المنازل عادةً لا تُحتسب فيها معامل القدرة بسبب استهلاكها المنخفض للطاقة، بينما تتعرض المباني التجارية والصناعية لعقوبات عند انخفاض معامل القدرة.
• 📉 يعتبر معامل القدرة الجيد بين 1 و0.95، بينما يكون السيء أقل من 0.85.
• ⚙️ الأحمال التحريضية، مثل المحركات، تتسبب في تأخر التيار عن الجهد، مما يؤدي إلى انخفاض معامل القدرة.
• 🔄 تحسين معامل القدرة يمكن أن يتم من خلال إضافة مكثفات للأحمال التحريضية أو أحمال استقرائية عند وجود حمولة سابقة.
• 🏗️ تحسين معامل القدرة يمكن أن يقلل من التكاليف ويزيد من كفاءة النظام الكهربائي في المباني الكبيرة.
• 💰 انخفاض معامل القدرة يؤدي إلى خسائر في المعدات الكهربائية وارتفاع الحرارة، مما قد يقلل من عمر المعدات.
• 📏 يتم تصحيح معامل القدرة باستخدام مكثفات بحساب الفرق بين الطاقة التفاعلية المطلوبة والموجودة في النظام.

Q & A

ما هو معامل القدرة وكيف يتم حسابه؟

معامل القدرة هو نسبة بين القدرة الحقيقية (kW) والقدرة الظاهرة (kVA). يتم حسابه باستخدام الصيغة PF = kW / kVA.

ما هي العلاقة بين الجهد والتيار في الأحمال المقاومة؟

في الأحمال المقاومة، تكون الجهد والتيار في نفس الطور، حيث يمر الجهد والتيار معًا عبر النقاط القصوى والدنيا ويعبرا المحور الصفري في نفس الوقت.

ما الفرق بين القدرة الحقيقية (kW) والقدرة الظاهرة (kVA)؟

القدرة الحقيقية (kW) هي القدرة المفيدة التي يتم استخدامها لأداء العمل، بينما القدرة الظاهرة (kVA) تمثل الجمع بين القدرة الحقيقية والقدرة غير الفعالة (kVAr).

لماذا تتقاضى شركات الكهرباء رسومًا على القدرة غير الفعالة؟

شركات الكهرباء تفرض رسومًا على القدرة غير الفعالة لأنها تسبب تدفقًا أكبر للتيار في الشبكة الكهربائية، مما يؤدي إلى انخفاض الجهد وتقليل قدرة التوزيع.

كيف يؤثر معامل القدرة السيء على الشبكة الكهربائية؟

معامل القدرة السيء يزيد من تدفق التيار عبر الشبكة، مما قد يؤدي إلى انخفاض الجهد، وزيادة الفاقد في المعدات، وزيادة تكلفة التركيب بسبب الحاجة لكابلات أكبر.

ما هي قدرة المحرك الذي لديه معامل قدرة 0.87؟

المحرك الذي لديه معامل قدرة 0.87 يحتاج إلى سحب 11.5 kVA لتوفير 10 kW من القدرة الحقيقية.

كيف يتم تحسين معامل القدرة باستخدام المكثفات؟

يمكن تحسين معامل القدرة بإضافة مكثفات إلى الدائرة الكهربائية لتقليل التأخير بين الجهد والتيار، مما يعيدهما إلى الطور ويزيد من معامل القدرة.

ما هو الدور الذي تلعبه القدرة غير الفعالة (kVAr) في المحركات الحثية؟

القدرة غير الفعالة تستخدم لتوليد المجال المغناطيسي الذي يدير المحرك، لكنها لا تساهم بشكل مباشر في إنجاز العمل.

كيف يمكن حساب القدرة الظاهرة (kVA) من القدرة الحقيقية ومعامل القدرة؟

لحساب القدرة الظاهرة، يمكن استخدام الصيغة: kVA = kW / PF. على سبيل المثال، إذا كانت القدرة الحقيقية 10 kW ومعامل القدرة 0.87، فإن القدرة الظاهرة ستكون 11.5 kVA.

ما هي المعايير التي تحدد ما إذا كان معامل القدرة جيدًا أو سيئًا؟

معامل القدرة يعتبر جيدًا إذا كان بين 1 و 0.95، وسيئًا إذا كان أقل من 0.85. المباني التجارية تكون عادة بين 0.98 و 0.92، بينما يمكن أن تكون المباني الصناعية أقل من 0.7.

Outlines

00:00

⚡ Introduction to Power Factor and its Importance

In this introductory paragraph, the speaker, Paul from TheEngineeringMindset.com, explains that the video will focus on the concept of power factor. Starting with simple analogies, the video will gradually delve into more technical details. Paul introduces the beer analogy to explain the relationship between true power (useful energy) and reactive power (waste energy), and how power factor measures the efficiency of energy usage in alternating current circuits. The formula for power factor, PF = KW / kVA, is also mentioned, emphasizing its relevance in both individual equipment and entire building energy consumption.

05:01

🍺 The Beer Analogy for Power Factor Explained

This paragraph dives into the beer analogy in detail, where true power (useful energy) is compared to beer, and reactive power (waste energy) is likened to foam. The power factor is the ratio of beer to foam, representing how efficiently energy is used. Paul explains that even though reactive power (foam) is unavoidable, reducing it leads to better efficiency and value for money. The concept of power triangles and trigonometry is introduced to explain power factor in electrical engineering, though the video focuses on simpler explanations for now.

10:03

🏢 Power Factor in Commercial and Industrial Settings

Paul discusses how power factor is typically not a concern for residential users but is crucial for commercial and industrial buildings. He explains that poor power factor can lead to additional charges on electricity bills due to the increased current flow through the electrical grid. This additional current can strain the network, cause voltage drops, and even overload cables. Penalty charges are often imposed when power factors drop below 0.95, especially in large buildings, affecting electricity suppliers’ ability to distribute power effectively.

🔧 Example: Comparing Two Motors with Different Power Factors

This paragraph presents an example comparing two induction motors, both delivering 10 kilowatts of power but with different power factors. One motor with a lower power factor (0.87) consumes more electricity than the other (0.92) to do the same amount of work, meaning it’s less efficient. Paul explains how to calculate kilovolt-amperes (kVA) and reactive power (kVAr), demonstrating how a lower power factor results in higher overall energy consumption and costs.

🌀 Causes of Poor Power Factor

In this section, Paul explains that poor power factor is often caused by inductive loads such as induction motors, which create a phase shift between voltage and current. He contrasts this with resistive loads, where voltage and current are in sync, resulting in a perfect power factor of 1. He also explains how reactive power is necessary to create magnetic fields in motors, although it doesn't contribute to doing actual work, leading to inefficiencies.

⚙️ Correcting Poor Power Factor

Paul outlines solutions for correcting poor power factor, primarily through the use of capacitors or inductors. For lagging power factors (caused by inductive loads), capacitors are added to realign current with voltage. Conversely, inductive loads are added to correct leading power factors (caused by capacitive loads). The goal is to bring the power factor closer to 1, reducing energy waste and avoiding penalties from electricity suppliers.

💡 Why Fixing Power Factor is Important

This paragraph stresses the importance of improving poor power factor to avoid higher energy costs and penalties from electricity suppliers. Paul highlights how poor power factor can lead to larger installations, increased heat losses, and reduced equipment lifespan. Fixing the power factor can improve energy efficiency, reduce losses, and extend the lifespan of electrical systems.

📐 Capacitor Calculations for Power Factor Correction

In the final paragraph, Paul walks through a simplified example of how to calculate the size of a capacitor needed to correct a building's power factor. Starting with a building that has a power factor of 0.78, the aim is to improve it to 0.96 to avoid penalty charges. He calculates the required reactive power and explains how the capacitor compensates for the difference, using specific formulas to find the correct size for the capacitor.

👋 Conclusion and Further Learning Resources

Paul wraps up the video by encouraging viewers to continue learning through other related videos. He invites questions in the comments section and reminds viewers to follow TheEngineeringMindset.com on social media platforms for more educational content.

Keywords

💡معامل القدرة

معامل القدرة هو رقم بدون وحدة يستخدم في دوائر التيار المتردد. يمثل نسبة القدرة الحقيقية إلى القدرة الظاهرية. في الفيديو، يُشبَّه معامل القدرة بنسبة البيرة إلى الرغوة في كأس، حيث البيرة تمثل القدرة الحقيقية التي نقوم بالدفع مقابلها والرغوة تمثل القدرة التفاعلية غير المفيدة.

💡القدرة الحقيقية

القدرة الحقيقية، أو الكيلوواط، هي القدرة التي تقوم بعمل فعلي. في الفيديو، يُشار إليها بالبيرة في تشبيه الكأس. هذه هي القدرة التي نحتاجها ونستفيد منها وتقوم بالعمل المطلوب.

💡القدرة الظاهرية

القدرة الظاهرية، أو الكيلو فولت أمبير، هي مجموع القدرة الحقيقية والقدرة التفاعلية. يتم دفع هذه القدرة ولكنها تشمل القدرة غير المفيدة أيضاً. في تشبيه الكأس، هي مجموع البيرة والرغوة معاً.

💡القدرة التفاعلية

القدرة التفاعلية، أو الكيلو فولت أمبير التفاعلية، هي القدرة غير المفيدة التي لا تقوم بعمل فعلي ولكنها ضرورية لإنشاء والحفاظ على المجال المغناطيسي في المحركات الحثية. في تشبيه الكأس، تمثل الرغوة.

💡الرغوة

الرغوة في تشبيه الكأس تمثل القدرة التفاعلية. هي الجزء غير المفيد من القدرة التي لا تقوم بعمل فعلي ولكنها موجودة ونضطر للدفع مقابلها.

💡المحركات الحثية

المحركات الحثية هي مثال على الأحمال الحثية التي تؤدي إلى معامل قدرة سيء. تحتاج هذه المحركات إلى القدرة التفاعلية لإنشاء المجال المغناطيسي الذي يدير المحرك، مما يؤدي إلى فرق زاوي بين التيار والجهد.

💡التصحيح القدرة

تصحيح القدرة يتضمن إضافة مكثفات أو محاثات إلى الدائرة لتحسين معامل القدرة وتقليل الفاقد التفاعلي. الهدف هو إعادة التيار والجهد إلى تزامن أفضل وجعل معامل القدرة أقرب إلى الواحد.

💡الجهد والتيار

في الأحمال المقاومة، يكون الجهد والتيار متزامنين، مما يعني أن معامل القدرة يكون واحداً. في الأحمال الحثية أو السعوية، يتخلف التيار عن الجهد أو يسبقه، مما يؤدي إلى معامل قدرة أقل.

💡المكثفات

المكثفات تُستخدم لتحسين معامل القدرة في الأحمال الحثية. عند إضافتها، تعوض القدرة التفاعلية السالبة، مما يقلل من الفاقد التفاعلي ويحسن معامل القدرة.

💡الأحمال الحثية

الأحمال الحثية مثل المحركات الحثية والمصابيح الفلورية تتسبب في تخلف التيار عن الجهد، مما يؤدي إلى معامل قدرة متأخر. تحتاج إلى القدرة التفاعلية لإنشاء المجالات المغناطيسية اللازمة لتشغيلها.

Highlights

Introduction to power factor using simple analogies and then advancing into electrical engineering concepts.

Power factor is a unitless number used in alternating current circuits, representing the ratio between true power (kW) and apparent power (kVA).

The beer analogy is used to explain power factor: beer represents true power (kW) and foam represents reactive power (kVAR), with the glass as the total apparent power (kVA).

A good power factor means more true power (beer) and less reactive power (foam), providing better value for the electricity consumed.

Power factor expressed using the power triangle, where true power (kW) is the adjacent line, reactive power (kVAR) is the opposite, and apparent power (kVA) is the hypotenuse.

Industrial and commercial buildings often see reactive power charges if their power factor falls below 0.95, leading to increased current flow and voltage drops in the electricity network.

In commercial buildings, good power factor ranges from 1 to 0.95, poor power factor is between 0.95 and 0.85, and bad power factor is below 0.85.

Example comparing two induction motors: both provide 10 kW of work, but the one with a lower power factor requires more kVA, leading to higher electricity costs.

Inductive loads like induction motors cause a lagging power factor, as the magnetic field in the coils delays the current relative to the voltage.

Reactive power (kVAR) is necessary to create magnetic fields in motors but does not perform useful work, resulting in inefficiencies.

Correcting poor power factor involves adding capacitors to counteract inductive loads or adding inductors for capacitive loads, bringing the power factor closer to 1.

A poor power factor means drawing more power from the grid to do the same amount of work, leading to higher costs, larger cables, and potential penalties from electricity suppliers.

Capacitor calculations for power factor correction: using formulas to improve the power factor of a building from 0.78 to 0.96, requiring a 25.5 kVAR capacitor.

Importance of power factor correction to avoid penalties, reduce energy losses, and extend the life of equipment by reducing voltage drops and overheating.

Closing remarks encouraging further learning through additional videos and interaction on social media platforms.

Transcripts

Hey there guys.

Paul here from TheEngineeringMindset.com

In this video, we're going to be discussing

power factor, we're going to start off really

easily with some simple analogies

to help you understand the basics, and then

we'll advance it into electrical

engineering terms with some work examples

as well as looking at what is power factor,

what is a good and bad power factor,

what causes bad power factor,

and how to fix bad power factor.

So what is power factor?

Power factor is a unitless number

using alternating current circuits.

It can be used to refer to a single piece of

equipment such as an induction motor or through

electricity consumption of an entire building.

In either case, it represents the ratio between

true power and apparent power.

The formula being PF equals KW divided by kVa.

So what does that mean?

My favourite analogy to explain this

is to use the beer analogy.

We pay for beer by the glass, but inside the glass

there is both beer and foam.

The more beer we have, the less foam there will be, so

we get very good value for money.

If there is a lot of foam, then there's not a lot of beer,

and so we're not getting very good value for money.

The beer represents our true power or kW, our kilowatts.

This is the useful stuff you want and need.

This is what does the work.

The foam represents our reactive power, or our

kVar, Kilovolt-Amps Reactives.

This is the useless stuff, there will always

be some, we have to pay for it, we can't use it

so we don't really want much of it.

It does actually have a use and a purpose,

but we'll see why later in the video.

The combination of these kW are kilowatts

and the kVar are Kilovolts-Amp Reactive,

is our apparent power or our kVA, meaning

the kilovolt amps.

Power factor is therefore

the ratio of useful power or true power

in kilowatts, or kW divided by what we're

charged for in kVA, kilovolt-amps.

So it's telling us how much value for money

we're getting for the power we consume.

If we briefly touch on electrical engineering,

and I will keep this part brief, then we might

see this express as a power triangle.

In this case I'll draw it as leading

power factor as it's easier to visualize.

The beer or true power is the adjacent line.

Then we have the foam which is the reactive

power on the opposite.

Then for the hypotenuse side, which is the

longest side, we have the apparent power.

This is at an angle from the true power, the

angle is known as theta.

You see as the reactive power or the foam

increases then so does the apparent power

of the kVA.

WE could then use trigonometry

to calculate this triangle.

I won't in this video as I'm just covering the basics,

so we'll just see the formulas you need,

but we'll do some calculations

and worked examples later in this video.

If we look at a typical residential

electricity bill, then we'll typically see

just a fee for the amount of kilowatts

hours used, because the power factor

and the electricity consumption will

be very low.

So the electricity companies

tend to not worry about this.

However on commercial and industrial electricity invoices,

especially buildings with smart

or interval electricity meters, then we'll

likely see charges and information

for the amount of kilowatts, kilowatt hours,

kilovolt amps, and kilovolts-amps reactive used.

Large buildings in particular will often

see reactive power charges in there.

But this depends on the electricity supplier,

and the agreement they have with the consumer.

They reason they charge a penalty for this

is because when large consumers have bad

power factors, they're increasing

the current flow through

the electricity network, and causing voltage drops,

which reduces the supplier's distribution

capacity and has a knock on effect

for the other customers.

Cable are rated to handle

a certain amount of current flowing for them.

So if a lot of large consumers connect

with bad power factor, then the cables could overload.

It could also struggle

to meet the demands and the capacity agreements,

and then no new customers will be able

to connect, until they either replace the cables,

or install additional cables.

Reactive power charges occur when the

power factor of a building falls below

a certain level.

This level is defined by

the electricity supplier, but it typically

starts around 0.95 and below.

A perfect power factor would be one, however

in reality, this is almost impossible to achieve.

We'll come back to this part

later in the video.

In large commercial buildings, the overall

power factor is likely to sit

in the following categories.

Good power factor is generally between one and 0.95

Poor power factor is anything from 0.95 and 0.85.

Bad power factor is anything below 0.85.

Commercial office buildings are usually somewhere

between 0.98 and 0.92.

Industrial buildings could be as low as 0.7.

We'll look out what causes this shortly.

Let's first have a look at an example.

If we compare two induction motors, that

both have an output of 10 kilowatts, and are

connected to a three phase 415/50 hertz supplier,

one has a power factor of 0.87, and the other

with the power factor of 0.92.

Both motors will deliver 10 kilowatts of work,

but the first motor has a lower power factor

compared to the second one.

Meaning we're not getting as much value for money.

The first motor will need to draw

11.5 kVA from the electricity grid to provide

the 10 kilowatts of power, the second motor

will need to draw just 10.9 kVA from

the electricity grid to provide

the same 10 kilowatts of power.

This means the first motor has 5.7kVAr

and the second motor has just 4.3kVArs

Remember our kilowatts is the beer,

and that's the useful stuff.

The kVArs are the foam, that's the not so useful stuff.

The kVA is what we're going to pay for,

and that's the kilowatts and the kVAr combined.

How did I calculate that?

For kVA I use kilowatts divided by power factor

so 10 divided by 0.87 to get 11.5 kVa.

For kVAr I use the square root of kVA squared,

subtract kilowatts squared.

So the square root

of 11.5 kVA squared minus 10 kilowatts squared.

We could've also found the power factor

from the kilowatt and the kVA, using

10 kilowatt divided by 11.5 kVA.

We could've found the kilowatts from

the power factor and the kVA using 0.87

divided by 11.5 kVA to get 10.

So what causes poor power factor?

In most cases the power factor

is affected by inductive loads.

If we have a purely resistive load, such as

an electrical resistive heater, then the voltage

and the current wave forms would be in sync

or very close.

They would both pass through their maximum

and minimum point and then pass through

the zero axis at the same time.

The power factor in this case is one,

which is perfect.

If we drew a phaser diagram, then the voltage and

and current would be parallel.

So all the energy drawn from the electricity

supply goes into doing work.

In this case creating heat.

But if we took an inductive load, such as

an induction motor, then the coils

magnetic field holds back the current and results

in the phase shift where the voltage

and the current waveforms fall out of sync

with each other, so the current passes

through the zero point after the voltage.

This is referred to as a lagging power factor.

Earlier in the video,

I said the foam or the kVAr is useless.

That's not exactly true.

You actually need some reactive power to create

and maintain the magnetic field

which rotates the motor.

The reactive power is wasted in the sense

that we get no work from it.

But we still have to pay for it although we do need it

to be able to do the work in the first place.

If we drew a phaser diagram for a purely

inductive load, then the current would be at an

angle below the voltage line.

Meaning not all the electricity consumed is doing work.

If we took a purely capacitive load,

then the opposite happens

to the inductive load.

The voltage and current are out of phase, except

this time the voltage is held back.

This causes leading power factor.

Again this will mean that not all of the

electricity being used is being used to do work.

But we still have to pay for it regardless.

If we drew a phaser diagram for a

purely capacitive load, then the current line

will be at an angle above the voltage line,

as it's leading.

Correcting poor power factor.

What can we do to correct poor power factor

and reactive power charges?

In most case we come across lagging power factor

caused by inductive loads.

To correct poor power

factor, we can add capacitors or inductors to

the circuit, which will realign the current back

into phase and bring the power factor

closer to one.

If we have a lagging power factor, caused by

high inductive loads in the circuit,

then we add capacitors.

If we have a leading power

factor, caused by high capacitive loads, then we

add an inductive load to the circuit.

These need to be calculated, and we'll see

some example calculations of this

at the end of the video.

So why should we fix poor power factor?

Poor power factor means you need to draw more

power from the electricity network

to do the same amount of work, therefore

the cables need to be larger so the installation

is going to cost more money.

If the power factor becomes too low,

then the electricity supplier might charge you

a penalty fee or reactive power charge.

Poor power factor can cause losses

in the equipment, like transformers,

and leads to high heat gains.

It can lead to voltage drops and can even reduce

the life expectancy of equipment

in extreme scenarios.

Capacitor calculations for power factor correction.

Let's look at a simplified example of calculating

the size of a capacitor to improve

the power factor of a load.

The building has a three phase power supply

and has a total load of 50 kilowatts of work.

It also has a power factor of 0.78, but we

want it to be 0.96 to avoid penalty charges.

Currently the building has a total apparent power

or kVA value of 64.1 kVA and we find that

by just dividing the kilowatts, 50 kilowatts

by the power factor of 0.78.

It also has a reactive power of 40.1 kVAr.

We find that by taking the square root of the

kVA squared and subtracting it from

the kilowatts squared.

So take the squared root

of 64.1 squared minus 50 kilowatts squared.

Then we calculate what the value should be

if we had a power factor of 0.96.

SO our apparent power should be 52.1 kVA.

We find that from 50 kilowatts divided by

0.96 power factor.

Then we find our reactive power which is

the square root of the kVA squared

minus the kilowatts squared.

So the square root

of 52.1 kVA squared minus 50 kilowatts squared

which gives us 14.6 kVAr.

The capacitor therefore

needs to make up the difference between these.

So 40.1 kVAr minus 14.6 kVAr which equals

a 25.5 kVAr capacitor.

Okay guys, that's it for this video,

but if you want to continue your learning,

check out these videos here.

I'll catch you there for the next lesson.

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