Section 2 Direct Excitation (Brush Type); Introduction; Stator Assembly; Brush Holder And Brushes - DeWalt DXGN4500 Manual

Direct Excitation (Brush Type)
Section 2

Introduction

See Figure 1-1. A typical brush type portable generator
needs 4 major components to function: prime mover,
rotor, stator, and voltage regulator.
As the engine begins to rotate, residual magnetism from
the rotor creates magnetic lines of flux. The lines begin to
cut across the excitation winding and induce a small
voltage into the voltage regulator. The excitation voltage
will power the voltage regulator and the voltage regulator
will start to sense AC voltage from Wires S15 and S16.
The lower voltage from the sensing wires will cause DC
excitation to the rotor to be driven up until AC output is at
desired level of 240 VAC. Once the generator has
reached 240 VAC it will maintain the DC voltage,
regulating the alternator when loads are applied and
removed.
C
D
A. Rotor
B. Stator
Figure 1-1. AC Generator Exploded View

Stator Assembly

The stator has three windings wound separately inside
the can. Two are the power windings and are located on
Wire 44 (Hot) and Wire 33 (Neutral); the other winding is
located on Wire 11 (Hot) and Wire 22 (neutral). The third
winding is called excitation winding and is located on
Wire 2 and Wire 6.
Some generators have color coded wires. Always use
the appropriate schematic and wiring diagram for unit.
Diagnostic Repair Manual
A
B
C. Brushes
D. Voltage Regulator

Brush Holder and Brushes

The brush holder has a positive (+) and a negative (-)
brush, and is retained to the rear bearing carrier by
means of two Taptite screws. Wire 4 connects to the
positive (+) brush and Wire 0 to the negative (-) brush.
Rectified and regulated excitation current is delivered to
the rotor windings via Wire 4, and the positive (+) brush
and slip ring. The excitation current passes through the
windings to the negative (-) slip ring and brush on Wire 0.
This current flow creates a magnetic field around the rotor
having a flux concentration that is proportional to the
amount of current flow.
A.
B.
Figure 1-2.

Voltage Regulator

See Figure 1-3. Unregulated AC output from the stator
excitation winding is delivered to the regulator DPE via
blue excitation winding wires. The voltage regulator
rectifies that current and, based on stator AC power
winding sensing, regulates it. The rectified and regulated
excitation current is then delivered to the rotor windings
from the positive (+) and negative (-) regulator terminals,
via red field positive and white field negative wires. Stator
AC power winding "sensing" is delivered to the regulator
via the green and white wires.
Figure 1-3.
B
A
11