The Magnetron ignition coil was produced by Briggs & Stratton as its first fully electric ignition system. These systems began to replace the older breaker point ignition designs in small, air-cooled engines when Briggs & Stratton produced them in the 1980s. As of 2011, the Magnetron ignition coil design has completely replaced the older design in these smaller engines.
Ignition coils operate on the physical phenomenon known as induction. This is the process whereby magnetic fields generate electric fields, and electric fields generate magnetic fields. This effect is magnified when the fields are moved past each other. Ignition coils generate an electrical field by rotating a coil, with a current-induced magnetic field, around a wire carrying an electrical current.
The action of an ignition coil acts as a closed circuit, keeping the current on the ignition coil itself. Breaker point systems work through a spinning distributor shaft with cams, or lobes, to push down stationary breaker points. When the cams push down the breaker points, the ignition coil's circuit is complete. When the cams rotate away and release the breaker points, then the circuit is broken. When the circuit breaks, the electrical field is no longer grounded and travels through the coil to the distributor cap.
The mechanics of a Magnetron ignition are almost identical to the workings of a breaker-point ignition: a complete circuit on the ignition coil grounds the electrical field it is generating so it stays on the circuit. But, whereas the breaker point system uses a mechanical set of breaker points and cams to push them down, the Magnetron coil uses a transistor to break and close the coil circuit.
Ignitions that use Magnetron coils are primarily found in low-horsepower engines. These engines can be adapted to work in push lawnmowers, riding lawnmowers, and other outdoor utility devices, such as snowblowers. Hobbyists also use them in motorized karts. The design of the Magnetron coil makes maintenance for these devices simpler, since its solid state design eliminates most of the moving mechanical parts. This leaves fewer items that can fail or need adjustment.
