Suulakepuristamalla

Suulakepuristamalla, literally "shorting the coil" in Finnish, refers to a technique in which an electric coil (inductor) is intentionally short‑circuited by placing a very low‑resistance path across its terminals. The abrupt interruption of current flow causes the magnetic field stored in the inductor to collapse quickly. According to Faraday’s law, a changing magnetic flux induces a voltage across the coil that can be many times larger than the supply voltage. The resulting high‑voltage, high‑frequency pulse is used to generate sparks, drive high‑speed relays, or shape short bursts in pulse‑power experiments.

The theoretical basis is the energy stored in the magnetic field, W = ½ LI², where L is inductance and I is current. When the coil is shorted, the energy is released as an electric impulse. The peak voltage Vp can be approximated by Vp = L (di/dt), where di/dt is very large during the brief switch‑off. Practical implementations often use a fast‑blow fuse or a semiconductor switch such as a MOSFET or IGBT to control the short, allowing precise timing and minimizing damage to the coil.

Typical applications include spark gap initiation in high‑voltage test rigs, demonstrating electromagnetic induction in educational labs, and as a driving method for magnetic switches or electromagnetic brakes. In industrial settings, shorted‑coil techniques are sometimes employed in contactless power transfer or as a means of generating high‑impedance loads for testing rectifiers and converters.

Safety considerations are paramount. The high‑voltage spikes can pose shock hazards, and the sudden release of energy can damage components. Protective enclosures, proper grounding, and current limiting resistors are commonly employed. Additionally, the write‑down of the coil’s inductance and careful selection of switching devices prevent overheating and arcing that could otherwise compromise the system’s reliability.