Notes on selection

The following conditions should be maintained when selecting the overvoltage protection:

• The limit voltage of the overvoltage protection V_RRM55 must not exceed the highest periodic and permissible peak blocking voltage of the power semiconductor to be protected.
• The rated supply voltage of the overvoltage protection must not be exceeded.
• Commutation overvoltages of the converter that periodically occur must remain below the response voltage of the overvoltage protection. The energy absorption capability of the selected overvoltage protection should be checked. A distinction must be made between two operating cases:
  
  • Transformer is shut down under no-load conditions
  • Transformer is shut down under load

Detailed notes on configuration, standards and connection of the overvoltage protection are provided in the operating instructions or on the Internet at
http://support.automation.siemens.com/WW/view/en/18260008/130000.