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Operating mechanism HMC

Designed for reliable switching

  • 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

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