SENDER-TEMPERATURE 5I7578 - Caterpillar

The field winding uses DC voltage to create a magnetic field. The magnetic field magnetizes the rotor. The rotor rotates the magnetic field on the inside of the stator. The stator generates AC voltage. The rectifier changes the AC voltage into DC voltage. Part of the DC voltage returns to the field winding in order to maintain the magnetic field. The remainder of the DC voltage is supplied to the battery and to the electrical systems through battery terminals.Alternator Operation Schematics
Illustration 1 g00825115
Electrical Schematic of the M1 Series Alternator (35 amp)
Illustration 2 g00825116
Electrical Schematic of the M1 Series Alternator (50 amp)
Illustration 3 g00829818
Electrical Schematic of the HDB Series Alternators The illustrations above show the electrical schematics for the alternators.The alternator has two circuits: the charging circuit and the excitation circuit. The charging circuit functions during normal operation. The excitation circuit functions during normal operation and during start-up. An independent circuit exists for each phase of the stator. The phases are noted as "u", "v", and "w". All alternator schematics are similar except for the 35 amp alternator. The 50 amp alternators, the 65 amp alternator, the 80 amp alternator, and the 95 amp alternator have two extra diodes. The diodes are connected to the neutral point of the stator. The diodes add extra current to the output. The 35 amp alternator lacks the extra diodes. The descriptions that follow show the 35 amp alternator.Charging Circuit
The charging circuit supplies current to the battery and to the electrical systems. The stator windings generate three-phase AC voltage. The positive diodes and the negative diodes change the AC voltage into DC voltage. The DC voltage allows current to flow to the battery terminals.
Illustration 4 g00825118
Charging circuit with phase angle of 120°The flow of current at a 120° phase angle is shown in Illustration 4. The voltage is positive at the output of winding "u". The voltage is zero at winding "v". The voltage is negative at winding "w". The current path is described below:Winding "u", positive diode "u", the "B+" terminal, the "B-" terminal, negative diode "w", winding "w" and the neutral point.
Illustration 5 g00825120
Charging circuit with phase angle of 150°The flow of current at a 150° phase angle is shown in Illustration 5. Voltage is positive at the output of winding "u", positive at winding "v" and negative at winding "w". The current path is described below:Winding "u" and winding "v", positive diode "u" and positive diode "v", the "B+" terminal, the "B-" terminal, negative diode "w", winding "w" and the neutral point.Excitation Circuit (Normal)
The excitation circuit supplies current to the field winding (exciter) during normal operation. The alternator is self-excited. The rotor contains an iron core that acts as a rotating magnet. The rotating magnetic field induces voltages in the stator windings. The stator windings generate three-phase AC voltage. The exciter diodes and the negative diodes change the AC voltage into DC voltage. The DC voltage allows current to flow in the field winding. The current induces a stationary magnetic field in the field winding.