The DCREG, the thyristor converter by Santerno, may be used to power supply high inductive loads, such as electromagnets.
The application issues due to this type of load have been fixed by a control algorithm specifically developed for DCREG4 converters.
CLAMPING UNIT CU400 FOR DCREG
The special algorithm implemented in the DCREG4 allows fixing application issues due to the ohmic resistor series-connected to a high power inductor. The CU400 protects the DCREG4 against overvoltage generated when the magnet current conduction mesh unexpectedly opens. When this happens, the CU400 cuts off power supply to prevent overvoltage conditions from occurring. The energy accumulated in the magnet is “absorbed” and stored to a RC-type clamping circuit, where overvoltage is limited by a capacitor and dissipated by a resistor.
To ensure efficient clamping functionality, the CU400 unit must be connected directly to the DC side of the converter. To suppress the first current peak generated by the capacitor, the capacitor is precharged when the mains voltage (typically 400 VAC) is applied to the relevant terminals. If the conduction mesh opens or the cables connecting the magnet to the converter are cut off, the resulting voltage arc is limited by the clamping circuit, capable of suppressing overvoltage. This configuration is typically required in case of electromagnets installed on bridge cranes.