The Power Triangle

Reactive power is measured in units of kVAr (kiloVolt Amperes reactive), whilst ‘true power’ is measured in kW (kiloWatts). In general terms the lower the power factor, the greater the amount of reactive power required. The highest power factor is unity, 1 however some equipment can operate at power factors as low as 0.4. The power factor can be calculated from the power triangle shown above.

Some equipment used in industrial and commercial applications requires an amount of ‘reactive power’ in addition to the ‘true power’ requirements. This reactive power generates the magnetic fields which are essential for inductive electrical equipment (such as transformers, motors and welders) to operate.

Customers wishing to reduce or even eliminate reactive power charges can consider doing so by improving the site’s power factor, to a level close to unity, i.e. 0.95-0.97. This is possible by installing power factor correction equipment (PFC). PFC consists of capacitors with associated control and switchgear. Capacitors draw reactive power, but in an ‘opposing direction’ to that drawn by typical business plant and equipment. The net effect is a reduction in the amount of reactive power, and therefore a lower level of kVA which may in turn lead to a lower available capacity charge each month.