TENSOREX C+ Automatic Tensioning System for Rail Overhead Lines

The overhead contact system (also called overhead line equipment) for electric railways is subject to expansion and contraction of the wires due to temperature variation. To guarantee continuous electrical energy to the train, the contact wire height must remain constant. Tensioning systems are used to compensate for the expansion and contraction of the contact wire.

PFISTERER TENSOREX C+ is an automatic tensioning system that exerts a constant pulling force on the contact wire to maintain its tension. The main components are a spiral spring and a cam (pulley with variable radius).


How it Works

By means of a support cable, TENSOREX C+ exerts a constant tension on the contact wire, regardless of any changes in length due to temperature. The special spiral spring is firmly connected to two cams on the same shaft. The degree of rotation of the shaft results in a linear variable torque/moment, which is compensated for by the combination with the variable radius of the cam. This produces a constant pulling force over the entire device working range.

The compensating length of TENSOREX C+ ranges from 250 mm to 1100 mm, with the line tension force ranging from 4.5 kN to 40 kN. The current operating point can be read off at any time from the scale of the TENSOREX C+.


  • For railways and tramways;
  • Best solution for space-limited areas such as stations, tunnels and bridges;
  • Improve aesthetics.

Advantages of TENSOREX C+

  • Compact and lightweight: Easy handling and transportation
  • Maintenance-free: no spare parts, lubrication, or oiling is required
  • High precision hence high reliability
  • Easy to install: Delivered ready to install, no tensioning weights or assembling required – lower installation costs
  • Reduced risk of theft/vandalism since no tensioning weights are required
  • Reusable in the event of wire failures.

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