Cos ϕ vs. Power Factor λ

In power measurement technology, it is necessary to always integrate the power over the area. In the 50 hertz network, the smallest measurement interval is one sine half-wave, thus 10 milliseconds. To calculate the power, the area under the power curve is integrated over this period. In this example, integrating the green power curves above the zero line gives a value of 118 watts, while the larger red curve below the zero line has a value of minus 118 watts. The integral of the total power over 10 milliseconds gives a value of zero, indicating oscillating power, which is defined as reactive power. Although this reactive power loads our line and the transformer, it does not have to be generated as active power. In practice, all current harmonics are multiplied by the voltage fundamental oscillation to calculate the distortion reactive power. Since the basic voltage oscillation dominates and the other voltage harmonics usually do not play a major role, this can be neglected in the measurement technique.

Reactive power is a type of power that is present in an electrical network that is not used, but only serves to increase the network load and losses in the network.

There are the following types of reactive power:

• Fundamental reactive power
• harmonic reactive power/distortion reactive power
• unbalance reactive power
• modulation reactive power

There are different remedies for each type of reactive power.

Reactive power refers to the deviation between the apparent power displayed in a network and the actual active power used by the equipment.

Unbalanced reactive power occurs when loads in a three-phase network are loaded unbalanced. This can occur, for example, due to different power on the three phases L1, L2 and L3. Although the apparent power and the active power per phase are equal in this case, a reactive power results in the overall system, which is called unbalanced reactive power. To reduce this reactive power, one can use, for example, an unbalance compensation system that compensates for the unbalanced currents and thus minimizes the reactive power

Modulation reactive power is caused by large fluctuations in the modulation of the current, such as in oscillation pack controllers. Today, there are many different types of reactive power, which modern power analyzers such as the PQ-Box evaluate and record individually.

The collective total reactive power is the square sum of all reactive power types.

This collective total reactive power thus explains the deviation between active and apparent power. It should be noted that the collective reactive power never has a sign, since all reactive power types are summed squared and consequently the sign is always positive. Only the fundamental reactive power can have a sign. A minus sign if this is capacitive and a positive sign if this fundamental reactive power is inductive.

The use of a frequency converter serves as a practical example. In this case, a B6 bridge rectifier circuit with 4 diodes is installed before the drive. The three-phase voltages or currents are hereby rectified and sent to the input of the inverter. In Fig. No. 7, it is easy to see that the current and voltage are in phase, expressing a cosine phi of close to 1. However, power analyzers will indicate a large reactive power for this load, since the power factor (ratio of P to S) is 0.85. An analysis of the current shows that the fifth and seventh current harmonics are present in this case, up to 160A. These current harmonics result in a distortion reactive power.

Another video shows, on a practical example, the reactive power types on the basis of a phase angle control.