Magne Blast Circuit Breaker


This is a 3D model of a Magne Blast Circuit Breaker.

3D Model Annotations

Magne Blast Circuit Breaker

A magne blast breaker is an interchangeable interrupter used within metal clad switchgear. It is available for continuous current ratings of 1200 and 3000 amperes. Due to its design, it is relatively easy to remove and install, which reduces downtime should a breaker need to be replaced.

Spring Release Interlock

A series of springs, levers, and cranks, are used to discharge the opening and closing springs when the unit is removed from service (disconnected from the electrical system), or charge the springs when the breaker enters into service (connects to the electrical system).

Positive Interlock Roller and Interlock Switch

The positive interlock roller and interlock switch have several functions. The first function is to prevent the breaker being raised or lowered whilst the breaker is in a closed position. The second function is to prevent the breaker being closed when the breaker is not in the fully raised position. An electrical and mechanical interlock is provided, as the breaker can be operated both mechanically and electrically.


Bushings are used to connect the breaker to the electrical circuit. The purpose of bushings is to ensure current can pass to the breaker without the electrical potential of the breaker casing being raised. Bushings located on the control panel side are referred to as ‘Front Bushings’ whilst those located further from the control panel are referred to as ‘Rear Bushings’.

Closing Spring

The closing spring is used to connect the breaker to the electrical circuit. An electric motor and ratchet wheel are used to charge (compress) the spring. The motor rotates, which causes the ratchet wheel to rotate and the spring to compress linearly. Once the ratchet wheel has rotated approximately 180 degrees, a latch engages, and the driving mechanism is disengaged in order that no residual stress remains upon the ratchet wheel. The latch prevents the spring from releasing its stored residual energy, but it can be removed easily to release this energy and close the breaker. In the event of a power outage (loss of control voltage), the closing spring can be compressed manually using a hand ratchet; the spring is fully compressed when the closing spring indicator shows ‘Charged’.

Opening Spring

The opening spring is smaller than the closing spring and is used for disconnecting the breaker from the electrical circuit. It is possible to open the breaker electrically using a trip coil, or mechanically using a trip lever. Both methods disengage a trip latch, which releases the opening spring’s stored energy, leading to circuit interruption.

Arc Chutes

A series of electrical arc chutes are used to cool and safely extinguish the electrical arcs generated when the breaker interrupts load current (when the breaker moves from the closed to open position).


Ease of interchangeability is made possible using wheels located at the base of the breaker.


Busbars are usually housed within a busbar compartment. Each busbar contains one phase. Busbars are usually constructed of copper or aluminium.

Circuit Breaker Compartment

The circuit breaker compartment houses the main breaker equipment used to close and open the electrical circuit.

Metal Clad Switchgear

The entire switchgear is surrounded by a metal casing which is usually earthed.

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