Intermediate circuit
An intermediate circuit is an electrical device that, as an energy store, electrically couples several electrical networks on an interposed current or voltage level via a converter .
Use cases:
- Electrical consumers often need the energy at very short intervals (e.g. starting an engine), but the supplying sources (public energy supply networks / emergency generators / power supplies / batteries, etc.) can only provide the energy to a limited extent for very short intervals provide.
- Different alternating current networks do not have the same frequency and are therefore not synchronous. (For example, the public energy supply network in Europe works with 50 Hz, whereas the traction current network in Germany works with 16.7 Hz; an elevator drive must be supplied with a frequency of e.g. 0 to 400 Hz.)
- Different alternating current networks (e.g. energy supply networks of different countries) have the same frequency, but are in different phase positions.
- DC voltage networks can work at different voltage levels (e.g. 1.5 kV and 3 kV traction current networks).
- Uninterruptible power supply that supplies a load from an accumulator in the event of a power failure .
For this reason it is necessary to check the voltages or currents of the different networks
- adjust their effective values (see up-converter , down-converter for direct voltage systems / transformers , four-quadrant controllers for alternating-voltage networks);
- rectified in the event that energy is fed into the intermediate circuit (see rectifier );
- Inverters to be provided for networks that are fed from the intermediate circuit;
- the energy in an energy storage device ( electric capacitance / inductance / accumulator) - that is the intermediate circuit - latch.
There are three different procedures:
- DC voltage intermediate circuit: by means of an intermediate circuit capacitor with constant voltage and variable current (see also U converter (Voltage Source Inverter, VSI)).
→ E.g. application in most industrial converters ( frequency converters ) for small and medium power - DC link by means of a link choke with constant current and variable voltage (see also I converter (Current Source Inverter, CSI)).
→ E.g. use in HVDC transmission or (drive) converters with high output - Z-source -Zwischenkreis: the intermediate circuit is a capacitor / Induktivitätsnetzwerk which can be used for voltage boosting and voltage reduction. It is mainly used when the supply voltage is subject to strong fluctuations. In contrast to conventional intermediate circuit topologies , a downstream inverter must ensure that the intermediate circuit voltage is maintained by means of through commutation , since the intermediate circuit network must be operated as a forward converter or flyback converter , depending on the voltage requirement.
Individual evidence
- ↑ Comparison of Traditional Inverters and Z-Source Inverters for Fuel Cell Vehicles ( Memento of the original from December 5, 2008 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 200 kB), Miaosen Shen, Alan Joseph, Jin Wang, Fang Z. Peng, and Donald J. Adams
- ↑ Z-Source for Motor Drives (PDF; 555 kB) Power Drives and Motor Drives Laboratory at Michigan State University