Lennox XP16 Series Unit Information page 42

OUTDOOR FAN MOTOR
XP16−XXX−230−01 through 05, except
XP16−060−230−05)
All units use single−phase PSC fan motors which require a run
capacitor. In all units, the condenser fan is controlled by
the compressor contactor.
ELECTRICAL DATA tables in this manual show
specifications for condenser fans used in XP16's.
Access to the condenser fan motor on all units is gained
by removing the four screws securing the fan assembly.
See figure 24. The grill fan assembly can be removed
from the cabinet as one piece.The condenser fan motor is
removed from the fan guard by removing the four nuts
found on top of the grill.
REMOVE
SCREWS
REMOVE
SCREWS
Figure 24. Removing Fan Grille
ALIGN FAN HUB FLUSH WITH END OF SHAFT
Figure 25. Aligning Fan Hub
XP16−060−230−05 Only
The variable speed condenser fan motor (figure 26) used in all
units is a three-phase, electronically controlled d.c. brushless
motor (controller converts single phase a.c. to three phase
D.C.), with a permanent-magnet-type rotor, manufactured by
GE. Because this motor has a permanent magnet rotor it does
not need brushes like conventional D.C. motors. The motors
consist of a control module and motor. Internal components are
shown in figure 26. The stator windings are split into three poles
which are electrically connected to the controller. This
arrangement allows motor windings to be turned on and off in
sequence by the controller.
The controller is primarily an A. C. to D. C. converter.
Converted D. C. power is used to drive the motor. The
controller contains a microprocessor which monitors
varying conditions inside the motor (such as motor
workload).
The controller uses sensing devices to know what position
the rotor is in at any given time. By sensing the position of the
rotor and then switching the motor windings on and off in
sequence, the rotor shaft turns the blower.
Figure 26. Variable Speed Fan Motor (XP16−060−230−05
The condenser fan motor is a variable speed motor with RPM
settings at 700 (Y1) and 820 (Y2). The variation in speed is
accomplished each time the controller switches a stator
winding (figure 27) on and off, it is called a pulse." The length
of time each pulse stays on is called the pulse width." By
varying the pulse width the controller varies motor speed
NUTS (4)
(called pulse-width modulation"). This allows for precise
control of motor speed and allows the motor to compensate for
varying load conditions as sensed by the controller. In this
case, the controller monitors the static workload on the motor
and varies motor rpm in order to maintain constant airflow
(cfm).
Motor rpm is continually adjusted internally to maintain
constant static pressure against the fan blade. The controller
monitors the static work load on the motor and motor
amp-draw to determine the amount of rpm adjustment.
Blower rpm is adjusted internally to maintain a constant cfm.
The amount of adjustment is determined by the incremental
taps which are used and the amount of motor loading sensed
internally. The motor constantly adjusts rpm to maintain a
specified cfm.
When line voltage is applied to the motor, there will be a large
inrush of power lasting less than 1/4 second. This inrush
charges a bank of DC filter capacitors inside the controller. If
the disconnect switch is bounced when the disconnect is
closed, the disconnect contacts may become welded. Try
not to bounce the disconnect switch when applying power to
the unit.
Page 42
RED
YELLOW
BLACK
RED
BLUE
only)
BLOWER MOTOR COMPONENTS
STATOR (WINDINGS)
ROTOR
Figure 27. Fan Motor Components
Internal Operation
Initial Power Up
motor
control module
BEARING
OUTPUT SHAFT
XP16