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Operating mechanism HMC

Designed for reliable switching

30 years of experience in design and manufacturing of operating mechanisms, with more than 100,000 units delivered to more than 100 different applications has resulted in the new HMC:

  • Highest switching reliability by using new design principles such as
    • cylinder made from gray cast iron and steel
    • new robust valve technology
    • wiper protected sealing systems
    • gearless pump unit
    • integrated close-interlocking with damage-free design
  • Lowest life-cycle cost due to
    • being maintenance-free for 10,000 CO-operations
    • easily accessible and exchangeable modules
  • Shortest time-to-market due to
    • simple and easy adaptation to all circuit-breaker types
    • compatible interface with HMB
    • nearly identical travel curve as HMB, allowing alternative operating mechanisms test according to IEC62271-100


  • Suitable for circuit-breaker applications up to 245 kV (HMC-1 and HMC-2) and up to 550 kV (HMC-4)
  • Live tank breakers (LTB)
  • Gas-insulated switchgear (GIS)
  • Dead tank breakers (DTB)
  • Hybrid systems
  • Operating mechanisms of type HMC can be also used for breakers outside the high-voltage application: Generator circuit-breakers (GCB)

Why Hitachi Energy?

  • 3rd generation of well proven operating mechanisms
  • State-of-the art technology with new design principles
  • Highest power density in the market for compact switchgear design
  • Modular design for high accessibility
  • Easy and fast adaptation to all circuit-breaker applications
  • Maintenance-free for 10,000 CO-operations
   HMC-1 HMC-2 HMC-4
Stored operating sequence  O-CO O-CO O-CO
Stored energy, last O [kJ]  up to 1.2 up to 2.2 up to 5.1
Stored energy, last C [kJ]   up to 0.6 up to 1.1 up to 3.5
Stroke [mm]  90 / 135 90 / 135 205 / 230

O = Opening of the circuit-breaker; C = Closing of the circuit-breaker
Specifications are subject to change without notice

Contact us

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