Power factor
This article explains the electrical engineering term power factor, other meanings under power factor (work study).
The power factor (also: active power factor) in electrical engineering is the ratio of the amount of active power 
to the apparent power 
. The ratio is expressed in the following formula:
The power factor can be between 0 and 1: 
Measuring device in the machine hall of the Zollern colliery
Impact factor
Exclusively for sinusoidal currents and voltages, the effective factor is defined from the ratio 
. It is equal to the cosine of the phase shift angle φ 
, see the graph opposite.
The amount of the effect factor is defined as the displacement factor.
Non-sinusoidal quantities contain, in addition to the fundamental, harmonics for which no uniform phase shift angle can be specified. In this case, the power factor λ 
cannot be specified as the effective factor 
. Harmonics are to be expected in particular in power supplies with conventional bridge rectifier, switching power supplies and loads containing semiconducting or magnetic components with non-linear characteristics.
In order to designate the characteristics of the load, the correct designation of the reactive power flow direction must be ensured. Clear designations are "inductive acting" and "capacitive acting" ( 
or 
in the load metering arrow system).
Power vector diagram and phase shift angle for sinusoidal voltages and currents in the complex plane
Meaning
In power supply installations, the aim is to achieve the highest possible power factor in order to avoid transmission losses. Ideally, it is exactly 1, but practically it is only about 0.95 (inductive). In motor systems with asynchronous machines, there is a risk of self-excitation if the reactive power is fully compensated. In addition, a capacitive power factor would lead to overvoltages on insulation of lines and electrical consumers. Power supply companies often prescribe a power factor of at least 0.9 for their customers. If the power factor falls below this value, the reactive energy purchased is billed separately. For private households, however, this is irrelevant. Power factor correction systems are used to increase the power factor. Since 1 January 2012, photovoltaic systems in Germany must also be capable of under-excited to overexcited between 0.9 or 0.95, depending on the size of the system, in order to stabilise the local grid voltage according to the requirements of the grid operator.
