Shunts replace transformers in large inverters to improve current metering performance

Isabellenhütte, Semikron and Siemens Drive Technologies have cooperated to develop a 3 phase shunt module for the Siemens SINAMICS G120 frequency inverter series. This series is intended for measuring phase currents of up to 20 A through shunts on the circuit board. Apart from this, currents of up to 400 A can be measured with outstanding precision and long-term stability using the jointly developed shunt modules in Semikron’s Semitrans housing.

The PM240 high-performance parts for SINAMICS G120 inverters make it possible to extend the current range of Isabellenhütte’s Type BVR electron-beam welded composite material precision resistors to 800 A and power output to 132 KW. For this purpose, the resistance of shunts used in this area was reduced from 3 to 1 mOhm, and the module’s layout was optimized. The housing’s interior was also adapted to the terminal link design. The isolated shunt installation, integration of 3 phases in one case and optimized power loss heat dissipation by a DCB substrate, as well as the module’s size, were not changed. Generally, the module’s resilience and reliability were improved. This means that users will still have a compactly built product with unprecedented value for money.

This new current measuring module is the first to permit measuring currents > 500 A in industrial serial application with four parallel SMD precision resistors with a deviation of less than 0.3 % in a temperature range between -25 °C and 125 °C. At the same time, the system’s drift throughout its life cycle is < 0.5 %. A prerequisite for this is the shunt’s resistance alloy, which was optimized for this purpose. Using shunt current measuring in this area of performance as well resulted in a very compact frequency inverter that may be used for operating engines with a power rate of up to 132 KW instead of the former 90 KW.

  agency, electronics, shunt