A typical ignition coil contains two sets of windings: a primary winding and a secondary winding. The primary winding utilizes thicker enameled wire, typically consisting of 200 to 500 turns of wire approximately 0.5 to 1 millimeter in diameter. The secondary winding employs much finer enameled wire, typically comprising 15,000 to 25,000 turns of wire approximately 0.1 millimeters in diameter. One end of the primary winding connects to the vehicle's low-voltage power supply (+), while the other end connects to a switching device (such as an interrupter). One end of the secondary winding connects to the primary winding, and the other end connects to the high-voltage output terminal to deliver high-voltage electricity.
Based on their magnetic circuit structure, ignition coils are primarily classified into two types: open magnetic circuit and closed magnetic circuit. The core of an open magnetic circuit ignition coil is typically a laminated structure; it exhibits higher magnetic reluctance and greater magnetic flux leakage, resulting in relatively lower energy conversion efficiency. Conversely, the core of a closed magnetic circuit ignition coil is shaped like a square ("口") or a rectangle ("日"); it features lower magnetic reluctance, minimal flux leakage, and high energy conversion efficiency. Furthermore, it is more compact in size and has become the dominant type in modern electronic ignition systems.
Additionally, to ensure high-voltage insulation and effective heat dissipation, the interior of an ignition coil is often filled with a dielectric medium, such as epoxy resin or insulating oil. With technological advancements, some modern ignition coils have become even more highly integrated. Mechanical structural designs also place greater emphasis on protective features-for instance, by incorporating additional protective components to enhance the coil's environmental adaptability and durability.
