معامل القدرة

معامل القدرة كما تظهر بالشكل الهندسي هو جيب التمام لزاوية الطور

معامل القدرة هوالنسبة بين القدرة الفعالة إلى القدرة الظاهرة وهومساوِ لجيب تمام زاوية الطور والتي هي فرق زاويتي الجهد والتيار لذا فهوقيمة عددية ليس لها وحدة قياس تتراوح من الصفر إلى الواحد ، في محطات القدرة يحبذ ويتم السعي إلى حتىقد يكون معامل القدرة أكبر ما يمكن حيث أنه بزيادة درجة معامل القدرة يزداد مقدارالقدرة الفعالة وتنخفض القيمة القدرة غير الفعالة أوالقدرة المخزنة وتتراوح قيم معاملات القدرة في محطات القدرة التي تعتمد نظام التيار المتردد بين 0,75 إلى 0,9 أما في محطات التيار المستمر فمعامل القدرة مساوِ واحد دوما لإن فرق زاويتي التيار والجهد يساوي صفر.

الدوائر الخطية

Instantaneous and average power calculated from AC voltage and current with a zero power factor (

ϕ

= 90°, cos(

ϕ

) = 0). The blue line shows all the power is stored temporarily in the load during the first quarter cycle and returned to the grid during the second quarter cycle, so no real power is consumed.

Instantaneous and average power calculated from AC voltage and current with a lagging power factor (

ϕ

= 45°, cos(

ϕ

) ≈ 0.71). The blue line shows some of the power is returned to the grid during the part of the cycle labeled

ϕ

.

الأهمية في نظم التوزيع

75 MVAr capacitor bank in a 150 kV substation

Power factors below 1.0 require a utility to generate more than the minimum volt-amperes necessary to supply the real power (watts). This increases generation and transmission costs. For example, if the load power factor were as low as 0.7, the apparent power would be 1.4 times the real power used by the load. Line current in the circuit would also be 1.4 times the current required at 1.0 power factor, so the losses in the circuit would be doubled (since they are proportional to the square of the current). Alternatively, all components of the system such as generators, conductors, transformers, and switchgear would be increased in size (and cost) to carry the extra current. When the power factor is close to unity, for the same KVA rating of the transformer more load can be connected.

Utilities typically charge additional costs to commercial customers who have a power factor below some limit, which is typically 0.9 to 0.95. Engineers are often interested in the power factor of a load as one of the factors that affect the efficiency of power transmission.

المراجع

^ "Power Factor – Importance, Calculation and Correction techniques". 23 November 2018.

وصلات خارجية

Harmonics and how they relate to power factor, U Texas, http://www.ece.utexas.edu/~grady/POWERFAC.pdf .
NIST Team Demystifies Utility of Power Factor Correction Devices, NIST, December 15, 2009, https://www.nist.gov/pml/div684/power_121509.cfm .
Power factor calculation and correction, US, http://www.powerfactor.us/ .