Belimo AFB24-SR - Page 30

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I
n
s
t
alla
t
io
n
I
n
s
tr
uc
t
io
n
s
Electrical Operatio
n
General
The AFB
,
AFX series actuators utilize both D
C
Motors and brushless D
C
motor
technology. The AFB, AFX uses this motor in conjunction with an Application
S
pecific
Integrated Circuit (ASIC). In the On/Off versions of the AFB and AFX, the ASIC
m
onitors and controls the actuator’s rotation and a digital rotation sensing function
to prevent damage to the actuator. The AFB24, AFX24… modulates type actuators
i
ncorporate a built in microprocessor. The microprocessor provides the intelligence
to the ASIC to provide a constant rotation rate and knows the actuator’s exact zero
p
osition.
Brushless DC Motor Operation
Belimo’s brushless D
C
motor spins by reversing the poles of stationary
e
lectromagnets housed inside of a rotating permanent magnet. The electromagnetic
p
oles are switched by a special A
S
I
C
circuit developed by Belimo. Unlike the
c
onventional DC motor, there are no brushes to wear or commutators to foul.
Overload Protection
The AFB, AFX series actuators are protected
f
rom overload at all an
g
les o
f
rotation.
The A
S
I
C
circuit constantly monitors the rotation of the D
C
motor inside the actuator
and stops the pulses to the motor when it senses a stall condition. The D
C
motor
r
emains energized and produces full rated torque to the load. This helps ensure that
dampers are fully closed and that ed
g
e and blade seals are always properly
c
ompresse
d
.
Motor Position Detection
Belimo brushless DC motors eliminate the need for potentiometers for positionin
g
in
m
odulatin
g
type actuators. Inside the motor are three “Hall Effect” sensors. These
sensors detect the spinnin
g
rotor and send pulses to the microprocessor which
c
ounts the pulses and calculates the position to within 1/3 of a revolution of the
m
otor.
Control Accuracy and Stability
-SR and MFT AF actuators have built
-
i
n brushless DC motors which provide
better accuracy and lon
g
er service life.
T
he -SR and MFT AF actuators are designed with a unique non-symmetrical
deadband. The actuator
f
ollows an increasing or decreasing control signal
with a 80 mV resolution. If the si
g
nal chan
g
es in the opposite direction, the
actuator will not respond until the control signal changes by 200 mV. This
a
ll
ows t
h
ese actuators to trac
k
even t
h
e s
li
g
h
test
d
ev
i
at
i
on very accurate
l
y, yet
allowin
g
the actuator to “wait” for a much lar
g
er chan
g
e in control si
g
nal due
to contro
l
s
i
gna
l
i
nsta
bili
ty.
8
8
Note: Resolution is a percenta
g
e o
f
operatin
g
ran
g
e. 1% in one direction,
2.5% when chan
g
in
g
direction. 2-10 VD
C
control example shown above
.
N40103 - 09/11 - Subject to change. © Belimo Aircontrols (USA), Inc.