Energy should be transmitted from the producer to the consumer in electric power supply networks. In networks operated with alternating current or three-phase current there is also a power that flows between the producer, the power station and certain electric consumers such as electric machines. This power is needed to generate the magnetic field of these machines. The level of this power is determined by the reactive power. However, reactive power makes no contribution the real power, i.e. the active power, so it cannot be utilised. The results of reactive power are the costs for the work it involves and transmission losses. This in turn can lead to a network expansion and its resulting higher CO2 emmissions.
The reactive-power requirement should be kept to a minimum. The inductive reactive-power requirement of an asynchronous machine can be compensated with a capacitor bank, a synchronous machine or a special current converter (power factor correction). This is defined as reactive power compensation. The energy required for generating the magnetic field then no longer flows in the supply network to the generator but only between the asynchronous machine and the capacitor bank or synchronous machine. This reduces the resulting current that is drawn for operation from the network by the drive.
There are different types of reactive power:
Displacement reactive power
This is caused by displacement of the angle between current and voltage
- Charged monthly on an average basis (contract with the power provider)
- Nowadays mostly compensated by reactor protected capacitors
Distortion reactive power
This is caused by harmonics in current and voltage
- Provided for when connecting high-performance current converters
- Compensation through filter circuits (passive, active)
Modulation reactive power
This is caused by periodic load fluctuations
- Caused by the connection of high-power welding machines, arcing furnaces etc.
- Compensation through dynamic compensation (SVC)
Asymmetric reactive power
This is caused by one and two-phase loads
- Provided for when connecting high-power converters such as welding machines and electric railways
- Balun as per Steinmetz, mostly dynamic with capacitors and reactors
The reactive-power compensation systems from PQM use capacitors to provide the inductive consumers with the reactive power they need thus reducing CO2 emissions, costs and transmission losses.