Understanding Solid State Frequency Converters

If solid state is determined to be the solution to your needs, then the rectifier design must be considered.


SSFCs with SCR rectifiers contain a risk that some components might be damaged during a reverse power condition. In this case, additional hardware (chopper with resistor, etc.) must be used to “burn” the reverse power, since it can not be transferred to the utility directly. Even with additional hardware, the inner components are stressed by higher voltages during the transition phase. This higher stress and a number of additional components will decrease the reliability of these units.

SSFCs with IGBT rectifiers will transfer the reverse power directly to the utility and thus do not need any additional hardware. Since no components are stressed by higher voltages created by the reverse power, the reliability of the unit is not decreased and there isn’t any additional risk of malfunction.

Conclusion
While 6-pulse SCR rectifier SSFC units are slightly cheaper than IGBT rectifier SSFC units, they have some significant drawbacks due to their effect upon the total system.
As energy prices continue to increase and power quality considerations and system reliability become more important, the construction of the input rectifier becomes a more important factor. IGBT rectifiers will optimize the energy consumption of the system and will reduce long-term operating costs providing users payback within a short time. The long- term investment for IGBT rectifiers is secured by eliminating the risk of “electrical pollution” and the negative influence to any other equipment on the same power system. In addition, they can handle reverse power conditions without any decline in the operating life time.

For further information please go to the White Paper section at www.piller.com.

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