Switching ON catenary voltage with no need of auxiliary power

Innovative AC Vacuum Circuit Breaker

Munich. For AC driven electric locomotives and multiple units Schaltbau has introduced an innovation of a special kind. It is an AC vacuum circuit breaker that can do almost 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.

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 10 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 energize 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 15 kV (16⅔ Hz) and 25 kV (50 and 60 Hz), the CVB Series vacuum circuit breaker is compliant to standards EN 60077-4, EN 50124-1, EN 60694, EN 50155 as well as EN 50121-3-2 and 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)
• Light-weight epoxy resin insulators
• Real-time monitoring and storage of operating data
• Rugged, reliable design, long service life, and low LCC costs

The switching element is a long-life vacuum switch tube with a hollow cylinder insulator member which is environmentally sealed at the ends. The breaker includes two M12 terminals for the connection to the line input from the pantograph and the main transformer as well as two corresponding cage clamps for the blade contacts of the earthing switch. The design and mechanism ensures maintenance-free operation at constant high contact pressure over the entire life cycle of the CVB without the need for readjustments.

The breaker’s drive and control system, which registers, among other things, multiple switching on/off and provides efficient short-circuit protection against it, works in the following way: Energy is stored by compressing a large powerful coil spring by means of an electric motor when the supply voltage is switched on. The mechanism is then latched without the need of any power being supplied. Once the spring is charged (<10 s) the CVB is ready for the next closing operation. All it takes to trip it is an electric impulse.

The trip latch mechanism makes use of the stored energy for a controlled closing operation (high acceleration, rapid movement damping) of the main contacts of the vacuum tube. With operating voltage being applied, a solenoid trip coil is energized holding the main contacts in closed position. Any interruption of the supply or operating voltage results in the de-energizing of the trip coil, which in turn triggers the controlled movement of a set of return springs as a positive means of opening the contacts and disconnecting the loads from the line input.

Contact

Schaltbau GmbH

Klausenburger Straße 6
D-81677 München

Press and Marketing

Phone +49 (0)89/93005-158
Fax +49 (0)89/93005-156
presse@schaltbau.de

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