Short Description

Gerapid high-speed DC circuit breakers are single-pole circuit breakers designed for use in railway propulsion-power distribution systems with operating currents up to 6000 A and operating voltages up to 800V dc. They have a very high interruption capacity combined with a current limiting characteristic.

Closing of the circuit breaker is performed through a high-power activation magnet. During inspections, opening and closing may be carried out by means of a hand lever, which can be mounted onto the armature of the activation magnet. Overload tripping is achieved directly via a short circuit trip or, depending on the rate of current rise, by an external current-rise release with an internal capacitor trip (ed - trip available as an accessory). Indirect remote tripping can be achieved by means of a shunt trip or an undervoltage release. The arc chute works on the basis of a highly sophisticated, asbestos-free, arc splitting principle. A wide variety of accessories and spares parts is available for maintenance, repair, or possible extension.

Structure and Components

Type Gerapid high speed DC circuit breakers have a compact and enclosed construction. They are IP 00 protected. All parts are mounted on thick-walled, non-breakable and fireproof insulation panels, whose large covers protect the breaker’s mechanism from damage. Transparent plastic side covers are available as an optional accessory to protect metal connecting elements on the panel.

Gerapid breakers are equipped with a two-stage contact system.  The main contacts are coated with a silver composite material; the arcing contacts are made from copper and can be easily replaced. The flexible contact is linked to the connection by means of very tight braids.

An attachment set is used to mount the various arc splitting systems for different operating voltages to the breakers. The arc chutes consist of a highly durable, arc-proof material, into which the arc plates have been integrated. The arc plates of split the arc into partial arcs and increase the arcing voltage by multiplying the anode and cathode voltage drop. Because of their high heat capacity, the plates and arc chute walls absorb a large amount of the arc’s energy.

The overload trip design uses a release magnet with twin magnets, optimizing the twin magnetic field principle. This technology ensures equally fast tripping in both current directions. The magnetic system does not require an auxiliary voltage. The system consists of the holding circuit, the flexible armature and the tripping circuit. The holding magnet and the tripping magnet are both excited by the main current. Until the static overload release’s response threshold has been reached, the flexible armature is held in position by the holding circuit’s magnetic field and the counter spring. If the main current exceeds the set static response threshold, the tripping circuit’s power takes over and pulls the flexible armature down suddenly.  During this operation, the armature trips the release lever. The main latch and contacts are opened immediately.  The response threshold can be easily adjusted by turning the adjustment nut with a SW6 hexagon wrench. In combination with the transparent side cover accessory, a fixed-mounted insulated knob is available (accessory).

To detect high short circuit currents early and to record leakage currents in long peripheral sections (for railway equipment), whose final values are lower than the highest operating currents, protective relays for monitoring a current increase should be installed.  If a fault occurs, a release signal can be passed on to the capacitor release, which causes the breaker to open rapidly (opening delay <3ms). This tripping mechanism can be ordered as an accessory for the breaker. (Alternatively, or additionally, it is possible to activate a shunt trip or an undervoltage release).

The breaker can be equipped with either a shunt trip or an undervoltage release. The shunt trip can be used for remote actuation.  The undervoltage release can be used for remote actuation and, in combination with an optional electronic trip unit incorporated into the breaker, for voltage control. Both trips work on a voltage level of 24V. A voltage transformer, which is integrated into the device, adapts to other voltage levels by transferring the energy required by the breaker mechanism (except for the drive). The release mechanism is tripped by potential free contacts at 24V level. The shunt trip is designed for short time action and is always connected through an auxiliary contact. This ensures that the shunt trip is only energized during the time until the breaker is opened. The undervoltage release’s winding is designed for continuous operation. In case of a voltage drop, the release mechanism opens the breaker. It is therefore possible to use the release in combination with the electronic trip unit for voltage monitoring, i.e. for motor switches, where an unintended re-start of machines after a temporary voltage breakdown is to be prevented. Due to their operational mode, undervoltage releases are self-monitoring devices, i.e. when the breaker is tripped upon a break of the pilot wire (EMERGENCY-OFF principle).

The activation magnet is mounted at the front of the breaker and is equipped with a grounded casing. The drive includes a self-interrupt control circuit (SU-control). This circuit enables a short activation with a minimum command duration of approximately 300 ms, causing the voltage applied to the magnet to be switched off after approximately 400ms and prevents, during continuous operation, repeated activation (anti pumping) due to an existing short circuit. In addition, the switch-in mechanism is electrically blocked for approximately 10s after activation. This prevents premature activation following a short circuit.

The breaker is equipped with up to ten isolated form C (1 NO/NC) auxiliary contacts. The auxiliary contacts are activated by the movable main contact.  They are wired to 15-pin control plugs. As an accessory, the circuit breaker can be equipped with auxiliary switches for indication of short circuit tripping and for the presence of the arc chutes.

Installation and Operation

Transportation

The circuit breaker must always be transported to the installation site properly and fully packed. The packaging protects the device against damage and dust; it should only be removed prior to installation. If the packaging is damaged, the breaker and the arc chutes must be inspected for damage.  Ensure that all packaging materials have been carefully removed prior to breaker installation.

Installation

The breakers, as delivered, are IP00 protected. They must be installed in a dry, preferably dust-free room. They must not be subjected to strong vibration.

The lower and upper connections must be connected directly to the main cables and busbars.

The breaker must only be used in an upright operating position with the arc chute in place and fully secured.  After installation, both the arc chute and special threaded joints must be checked for tightness.

The safety distances as shown in the dimensional drawings [Fig.9,10,11] must be maintained to grounded or insulated parts.  Suitable measures must be taken to protect personnel from arcs.

Strong, external magnetic fields caused by improperly located supply conductors or stray fields from other devices, can lead to a shift of the trip setting thresholds. This may result in premature tripping, or no tripping at all, during low-level short circuit current events. This has to be accounted for when installing and operating the device with shielding added if appropriate.

The control wires must be connected as shown in the schematic circuit diagram [Fig.23]. The protective grounding wire must be connected at the marked terminal.

Setting the Overload Release

The adjustment of the static overload release [Fig.1] within a specific adjustment range is made by turning the regulating screw. This procedure requires an SW6 hexagon wrench. The adjustment must only be carried out after the breaker has been disconnected from the main circuit and has been grounded.

Turning the adjustment screw clockwise decreases the trip threshold, turning the screw counter-clockwise increases the tripping threshold.  Adjustment is performed by aligning both the arrow and the marking line to one line.

Operation

Maximum operating voltage and current ratings are as shown on the breaker nameplate.

During continuous operation, it must be loaded with its rated operating current at maximum. Load currents in excess of breaker nameplate rating are allowable for brief periods. Refer to the short time currents listed in Table 1.  Do not exceed the rated operating voltage shown on the breaker nameplate.

The drive and auxiliary trips function within the specified control voltage range. The auxiliary trips must be loaded with the values listed in Table 1 at maximum.