Section 1 Capacitive Discharge (Brushless); Introduction; Rotor Assembly; Stator Assembly - DeWalt DXGN4500 Manual

Capacitive Discharge (Brushless)
Section 1

Introduction

See Figure 1-1. A typical brushless type portable
generator needs 4 major components to function: a prime
mover, rotor, stator, and capacitor.
As the engine begins to rotate, residual/permanent
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 winding. The voltage
causes the capacitor to charge.
A
A
B
A. Rotor
B. Stator
C. Capacitor
Figure 1-1. AC Generator Exploded View
The capacitor on the excitation winding takes the place of
a voltage regulator. It will charge until AC peaks, then as
AC starts to fade it will discharge causing a voltage to be
induced into the rotor.
Two diodes in the rotor convert AC voltage to DC. There
is a diode in one pole that is orientated in one direction,
and a diode in the opposite pole orientated in the
opposite direction. This produces a North and South
poled rotor.
In one rotation of the rotor, the capacitor will charge and
discharge twice, inducing AC voltage into the rotor.
A capacitor discharge generator will produce a lower
voltage until load is applied. Once load is applied, the
output voltage will increase due to induction into the
excitation winding and capacitor.
As load is applied, current in the main AC windings
increases. This increase in current is also induced into
the excitation winding
functions). The increased current into the excitation
Diagnostic Repair Manual
C
B
(much like a transformer
winding causes voltage to increase which also increases
the charge/discharge value of the capacitor. This creates
a stronger magnetic field in the rotor and higher AC
output.
NOTE: Voltage will only increase from no load to full load
and will stop increasing at that point.

Rotor Assembly

The 2-pole rotor must be operated at 3600 rpm to supply
a 60 Hertz AC frequency. The term "2-pole" means the
rotor has a single north magnetic pole and a single south
magnetic pole. It spins freely inside the stator can and is
excited by the charging and discharging of the capacitor.
The rotor has two diodes that rectify voltage induced from
the excitation winding to DC voltage. Each winding/pole
will have a diode orientated to create current flow in one
direction, and the other winding/pole will have a diode
orientated to create current flow in the opposite direction.
This creates a North and South pole.
A rotor bearing is pressed onto the end of the rotor shaft.
The tapered rotor shaft is mounted to a tapered
crankshaft and is held in place with a single through bolt.
NOTE: Some rotors have a magnet placed inside the
laminations to help excite the rotor after it has been left
idle for a long period of time.
A
B
A. Diode
B. Capacitor
Figure 1-2. Rotor and Diodes

Stator Assembly

The stator has three windings wound separately inside
the can. Two are power windings located on Black Wires
(Hot) and White Wires (Neutral). The third winding is the
excitation winding and is on the Red Wires.
Some stator assemblies may be configured differently.
Always use the appropriate schematic and wiring
diagram for unit.
A
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