Munich – Schaltbau has introduced a special innovation for AC-driven electric locomotives and multiple units: an AC vacuum circuit breaker that can almost do without any secondary supply energy for switching on the overhead wire voltage.

The energy needed for this operation is stored in a coil spring instead, which is locked mechanically. To release it a solenoid trip coil is activated which requires only such a small supply of power for its activation that it can be supplied even from a nearly flat battery.


The CVB series vacuum circuit breaker is used as main switch and protection device of AC driven railway vehicles. It is mostly roof-mounted between the pantograph and the main transformer.

The new CVB series is designed for breaking high current circuits, and as a cutout to protect against short circuit and overload conditions. It is predominantly used with new locomotives but also as a replacement of existing air circuit and vacuum circuit breakers. In this case the replacement can be accomplished without any modification of the roof top design. The CVB is also mechanically compatible with BTE-type roof earthing switches.

VACUUM CIRCUIT BREAKER WITH stored energy mechanism

The main feature of the CVB is its stored energy mechanism for fast, positive closing action. The energy necessary to move the main contacts is stored by compressing a powerful coil spring which is attached to the contact assembly of the circuit breaker.

When the stored energy is tripped, the spring is recharged in less than ten seconds by means of an electric motor, and the operating mechanism is latched so that the breaker is ready for the next closing operation. The latch may now be operated to release the spring, and the spring pressure will shut the circuit breaker.


The trip latch mechanism is remotely operated by means of a solenoid trip coil, so all it takes to trip the circuit breaker is the small supply of power needed to energise the trip coil.

Once the main contacts of the circuit breaker are closed, they are held in that position by the electromagnetic trip latch. If, however, there is a breakdown of the control on signal or a fault in the electrical supply system, the operating mechanism is unlatched and a set of return springs mechanically forces the closed breaker contacts open, disconnecting the supply from the electrical load (fail safe principle).

There is an electronic control unit that monitors the state of the main contacts, controls the spring charging motor, and ensures fail-safe operation even in an emergency. An interface to the control circuit of the railway vehicle is provided.


With voltage ratings of 15kV (16Hz) and 25kV (50Hz and 60Hz), the CVB series vacuum circuit breaker is compliant to EN 60077-4, EN 50124-1, EN 60694, EN 50155 and EN 50121-3-2 standards. It also has the following features:

  • Can be operated even with deep discharge vehicle battery
  • No trouble with low or insufficient air pressure
  • No trouble with low or rapidly changing temperatures
  • Fail safe principle: fault in electrical supply system trips a mechanism that causes the breaker contacts to move apart or disconnect, thereby breaking the circuit path
  • Redundant system (return springs)
  • Lightweight epoxy resin insulators
  • Real-time monitoring and storage of operating data
  • Rugged, reliable design, long service life, and low LCC costs