Generator Terminal Symbols: A Complete Guide

Generators typically feature terminals for the armature, field, ground, neutral point, etc. These terminals are marked with distinct letters—what do they represent? The experts at Dingbo Power explain in detail below:

1.Armature Terminal: The thickest terminal on an alternator, usually 6mm in diameter.

2.Field and Neutral Terminals: Generators have two thinner terminals (≈3mm diameter). One, with its screw base directly contacting the housing (or via a copper strip), is the ground terminal. The adjacent thin terminal is the field terminal, and a separate terminal serves as the neutral point.

3.Multimeter Identification:

Disconnect all wires from the alternator. Set the multimeter to "RX10" or "RX100" mode.

Connect one probe to the alternator housing. Touch the other probe to the two thin brush holder terminals:

0 resistance: Ground terminal.

Resistance reading: Field terminal.

The armature terminal shows high resistance to ground; the neutral terminal shows low resistance.

Terminal Letter Symbols and Meanings (Marked on the Rectifier End Cover):

(1)"A", "B+", or "B" (Battery): Armature terminal. Internally connects to the positive rectifier plate; externally outputs power via thick wires to the battery positive terminal and starter. Also denotes the main power output line.

(2)"F" (Field): Field terminal. For standard alternators, internally connects to one end of the excitation winding; externally links to the voltage regulator’s "F" terminal. In integrated alternators (with built-in IC regulators), the excitation winding’s regulator-connected end is also labeled "F".

(3)"N" or "P" (Neutral): Neutral point terminal. Internally connects to the star-wound stator’s neutral point. Externally, it controls relays (e.g., charge indicator, field relays) in standard alternators. In integrated alternators, it connects to the IC regulator (or a stator phase tap).

(4)"L" (Light): Charge indicator terminal. In integrated alternators, internally connects to the IC regulator (controlling the charge light); externally links to the ignition switch and charge indicator light.

(5)"D+": Charge indicator terminal (for 9/11-diode alternators with dedicated field diodes). The charge light is controlled via three field diodes; externally connects to the ignition switch and charge indicator.

(6)"S": Battery voltage sense terminal (common in high-power automotive alternators). Internally connects to the IC regulator; externally links directly to the battery positive terminal via an un-fused thick wire to detect alternator voltage, serving as the regulator’s reference signal.

(7)"E" (Earth) or "⊥": Ground terminal. For standard alternators, connects to the housing; externally links to the voltage regulator’s "E" or "-" terminal, ensuring a reliable ground circuit for the charging system.

(8) "IG" (Ignition): Ignition control terminal. Controls alternator operation; externally connects to the ignition switch and battery positive terminal.

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