AERCO Belimo AF120-S US Actuator - Manual (Page 7)

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Installation Instructions
Electrical Operation
General
The AF series actuators utilize brushless DC motor technology. The AF uses this
motor in conjunction with an Application Specific Integrated Circuit (ASIC). In the On/
Off versions of the AF, the ASIC monitors and controls the actuator’s rotation and a
digital rotation sensing function to prevent damage to the actuator. The AF24…
modulating type actuators incorporate 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 position.
Brushless DC Motor Operation
Belimo’s brushless DC motor spins by reversing the poles of stationary
electromagnets housed inside of a rotating permanent magnet. The electromagnetic
poles are switched by a special ASIC circuit developed by Belimo. Unlike the
conventional DC motor, there are no brushes to wear or commutators to foul.
Overload Protection
The AF series actuators are protected from overload at all angles of rotation. The
A
ASIC circuit constantly monitors the rotation of the DC motor inside the actuator and
stops the pulses to the motor when it senses a stall condition. The DC motor
remains energized and produces full rated torque to the load. This helps ensure that
dampers are fully closed and that edge and blade seals are always properly
compressed.
Motor Position Detection
Belimo brushless DC motors eliminate the need for potentiometers for positioning in
modulating type actuators. Inside the motor are three “Hall Effect” sensors. These
sensors detect the spinning rotor and send pulses to the microprocessor which
counts the pulses and calculates the position to within 1/3 of a revolution of the
motor.
Control Accuracy and Stability
AF24-SR US actuators have built-in
brushless DC motors which provide
better accuracy and longer service life.
The AF24-SR US actuators are designed with a unique non-symmetrical dead-
band. The actuator follows an increasing or decreasing control signal with a
80 mV resolution. If the signal changes in the opposite direction, the actuator
will not respond until the control signal changes by 200 mV. This allows these
actuators to track even the slightest deviation very accurately, yet allowing
the actuator to “wait” for a much larger change in control signal due to control
signal instability.
M40024 - 05/10 - Subject to change.
© Belimo
Aircontrols (USA),
Inc
.