Electrical Operation; Overload Protection; Motor Position Detection; Control Accuracy And Stability - Belimo AF24 US Manual

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 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.
800-543-9038 USA
40

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
deadband. The actuator follows an increasing or decreasing control sig-
nal with a 80 mV resolution. If the signal changes in the opposite direc-
tion, 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.
AF Actuator responds to a 80 mV signal
when not changing direction from stop
AF Actuator responds to a 200 mV signal
when reversing direction from stop position.
Minimum Reversed
Control Deadband
Prior to Normal Control
The AF24-MFT US control accuracy and stability can be found in the MFT
specifications, page 293.
866-805-7089 CANADA
Satisfied
Control Position
80 mV
Minimum
Control Resolution
200 mV
Satisfied
Control Position
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