Electropak Precision Engineering designs and manufactures blowout coils for the rail industry from our facility in Preston, Lancashire in the UK.
A blowout coil is an electromagnetic device used in electrical circuit breakers or contactors—especially in DC (direct current) circuits—to extinguish an arc that forms when a circuit is opened (i.e., when contacts separate under load).
Electropak have designed and supplied coils to UK and International Rail Operators and Engineering Firms.
In DC circuits, when the contacts open, the electric arc that forms is harder to extinguish than in AC circuits because there’s no natural current zero-crossing (as happens in AC 50/60 Hz systems). If the arc isn’t quickly extinguished, it can:
Cause overheating or fire
Prevent the breaker from fully opening
A blowout coil generates a magnetic field that acts on the arc. This magnetic field:
Deflects or stretches the arc away from the contacts
Moves it into an arc chute or splitter plates, where it can be cooled and safely extinguished
Increases the arc length, reducing the current density and aiding in arc extinction
The coil is connected in such a way that current flowing through it produces a magnetic field perpendicular to the arc.
Due to the interaction between the magnetic field and the arc (carrying current), a Lorentz force is exerted, pushing the arc away.
This is a form of electromagnetic blowout—hence the name.
Typical applications for coils include:
Electropak Precision Engineering is a UKC Group company.
On recent products manufactured for UK trains, Electropak developed unique specialist tooling and machinery to pre-heat the copper strip to anneal it as it was wound.
The tightly wound coils this process achieves enables the blowout coils to fit in a small envelope of space and reduce the risk of fire on the trains.
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