 Damping resistors
Application
Filter circuits are used to avoid negative effects on the grid of power systems. Large-scale induction smelters in aluminum or steel mills generate harmonic waves. These must be prevented from acting on the grid. To this effect filters are used, mostly in the form of T or L elements. A series resonant circuit at the inlet of the medium voltage feed consisting of a series connection of capacity and inductance act as a loader on the harmonic waves, thus damping them.
To prevent hazardous switching overvoltage at the reaction coil and increase the band width of the resonant circuit, the reaction coil L is dampened by a resistance R.
Usually, with the design of the filter the currents I0…n of the base wave and the harmonic wave f0…n and the resistance value are already set.
The resistance capacity is then calculated as follows
Or the complete resistance capacity and the resistance value are indicated.
These values can be used to calculate the current and the direct-axis voltage UL = UR:
When switching on, almost the entire loading current of the capacitor can flow across the resistor depending on the position of the vector, so that a surge load capacity of about
has to be considered.
Designs
Filter resistors are manufactured on the basis of steel grid resistors (chapter 2 of this catalogue).
For the design, the requisite number of elements are assembled to form one or several packages and combined in one or several mounting frames in consideration of the insulation for the system voltage.
The mounting frames are mounted on support insulators and installed with or without housing depending on the required protection class.
Housed resistors can be manufactured mounted on insulators with non-grounded or grounded casing.
Order information
- System voltage
- Insulation voltage (BIL)
- Nominal capacity or currents
- Initial current and time
- Resistance value
- Admissible manufacturing tolerance
- Admissible tolerance cold/hot
- Installation altitude above sea level
- Climatic and atmospheric conditions
- Ambient temperature range
- Indoor or outdoor installation
- Protection class
- Type of terminal connection
References
| Customer / Product |
System, model |
| ABB Capacitor Sweden |
DEH system from 30 kW |
| ABB Switzerland |
48
DEH system from 30 kW |
| Egesim |
DEH system |
| Emsby |
DEH system |
Text © GINO AG |
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