Ignition apparatus with secondary winding having reduced breakdown failures

摘要

An ignition apparatus (10) includes a secondary winding spool (28) having a secondary winding (30) wound thereon. The secondary winding (30) includes a low voltage end and a high voltage end (30HV) that is configured for connection to a spark plug (14). The secondary winding (30) at the high voltage end is configured in accordance with a predetermined radial thickness profile (80a or 80b) taken in the direction from the high voltage end towards the low voltage end. The profile is determined as a function of (1) a reflected voltage (26a) associated with the spark gap breakdown of the spark plug and (2) an induced voltage (26b) due to magnetic flux coupled through a central core (16). The profile is determined so as to reduce layer-to-layer voltage levels (26e) in the secondary winding near the high voltage end. The profile can be wound or can be molded in the secondary spool itself.