What unit contains a hold-in winding and a pull-in winding?

The starter solenoid is the component that contains both a hold-in winding and a pull-in winding. In the context of starting systems in vehicles, the starter solenoid serves a crucial purpose by acting as a relay that engages the starter motor when the ignition key is turned.

The pull-in winding is a high-current coil that generates a magnetic field to pull the solenoid's plunger into the engaged position when the ignition is activated. This action pushes the contacts together to complete the circuit to the starter motor, allowing it to start the engine.

Once the solenoid is engaged and the starter motor is running, the hold-in winding takes over. This winding provides a lower current to maintain the solenoid’s plunger in the engaged position, ensuring that the connection remains closed until the starter motor stops cranking.

In contrast, the field coil is involved in generating a magnetic field in an alternator or generator, the armature is a rotating part of motors and generators that interacts with magnetic fields to produce torque, and the ignition switch is simply the mechanism used to turn the ignition system on or off without the specific winding functions seen in the starter solenoid.