FUEL SHUT-OFF SOLENOID PULL-IN COIL CURRENT LIMITER

摘要

The pull-in coil of a fuel shut-off solenoid on an engine is connected to a thermistor circuit for limiting the current to the pull-in coil. The pull-in coil is connected to ground through terminals of a control relay and through a thermistor. The activation coil of the control relay is also connected to the thermistor. When power is initially supplied to the pullin coil, the resistance of the thermistor is low and current flow is sufficient to activate the fuel shut-off solenoid. The initial low resistance also assures that the voltage at the control relay activation coil remains near ground so the control relay initially remains deactivated. As the thermistor heats and resistance increases, pull-in coil current diminishes and voltage at the control relay increases until the control relay activates to interrupt power to the thermistor. The thermistor cools so that upon occurrence of the next pull-in solenoid activation pulse, the solenoid pullin coil will immediately activate.