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Operating Mechanisms

Operating mechanisms of type HMB and HMC from Hitachi Energy are designed for reliable switching in the entire product range of high voltage circuit-breakers from 52 kV to 1,100 kV.

The circuit-breaker constitutes the last link in the chain of different apparatus which form part of the protection equipment for power supply system. The operating mechanism is, besides the interrupter, the most important component of the breaker.

HMB and HMC allow for simple and easy adaptation to all circuit-breaker types, thus covering a wide range of applications.


  • Live tank breakers (LTB)
  • Gas-insulated switchgear (GIS)
  • Dead tank breakers (DTB)
  • Hybrid systems
  • Operating mechanisms of type HMB and HMC are also used for breakers outside the high-voltage application: Generator circuit-breakers (GCB)

Why Hitachi Energy?

  • 30 years of experience in design and manufacturing of operating mechanisms
  • More than 110,000 mechanisms of HM type  put in service
  • Highly adaptable products - more than 100 different applications
  • Low life cycle costs due to minimum maintenance requirements and modular design
  • Highest power density in the market for compact switchgear designs
Type HMB and HMC from Hitachi Energy

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