MAGNETO

permanent-magnet alternating generator employed when the output of energy required is very small. It is primarily designed to generate current for the ignition of compressed gases in various types of internal-combustion engines, such as those used in aircraft, marine, tractor, and motorcycle engines. The major parts of the high-tension magneto are a permanent-magnet rotor, an armature with a primary winding containing a small number of turns of coarse wire, a secondary winding with a large number of turns of fine wire, a cam-type circuit breaker, and a capacitor. As the magnetic rotor turns, it induces in the primary winding a current that charges the capacitor. The cam breaks the circuit of the primary winding when the induced current reaches its peak, and the magnetic field around the primary winding collapses. The capacitor discharges its stored current into the primary winding, inducing a reversed magnetic field. The collapse and reversal of the magnetic field induces a high-voltage current in the secondary winding that is distributed to the spark plugs for ignition.