508183-01
Issue 2114
Page 9 of 52
Indoor Blower Motor
Power Choke
(4 and 5 Ton Only) Blower Motor
(B3)
Figure 4.
During blower operation, the ECM motor emits
energy that may interfere with pacemaker operation.
Interference is reduced by both the sheet metal cabinet
and distance.
WARNING
The motor communicates with the integrated control via a
2-way serial connection. The motor receives all necessary
functional parameters from the integrated control and does
not rely on a factory program like traditional variable
speed
motors.
GUH96T
units use 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 (Figure 6). Because this
motor has a permanent
magnet rotor it does not need
brushes like conventional
D.C. motors.
The stator windings are split into three poles which are
electrically connected to the controller. This arrangement
allows motor windings to turn on and off in sequence by
the controller.
A solid-state controller is permanently attached to the
motor. 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 sense 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.
All
GUH9
6
T
blower motors use single phase power.
An external run capacitor is not used. The motor uses
permanently lubricated ball-type bearings.
MOTOR
CONTROLLER
J49
J48
Figure 5. GenTeq Blower Motor B3
STATOR
(WINDINGS)
OUTPUT
SHAFT
BEARING
ROTOR
Figure 6. Blower Motor Components
Internal Operation
Each time the controller switches a stator winding (Figure
6) 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 (Figure 8), the controller varies motor speed
(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).
The motor controller is driven by the Two-stage Variable
Speed Integrated control board.
Motor rpm is continually adjusted internally to maintain
constant static pressure against the blower wheel. The
controller monitors the static work load on the motor
and motor amp-draw to determine the amount of rpm
adjustment. Blower rpm may be adjusted any amount in
order to maintain a constant cfm as shown in blower tables.
The cfm remains relatively stable over a broad range of
static pressure. Since the blower constantly adjusts rpm to
maintain a specified cfm, motor rpm is not rated. Hence,
the terms “cool speed”, “heat speed” or “speed tap” in this
manual, on the unit wiring diagram and on blower B3, refer
to blower cfm regardless of motor rpm.
The unit control indicates the desired cfm. The blower
will maintain the desired cfm as long as external static
pressure does not exceed 0.8”. If the system exceeds this
amount, the blower may enter a “cut back”, mode wherein
it then slows down to protect itself from electrical damage.
During this “cut back” mode the unit control will still indicate
the same desired cfm regardless of actual motor rpm.
