Access Flow2A Manual page 27

27
The drive unit
To ensure that there will be no mismatch between the actual position and the position according to the pulse
counter, the pulse counter is reset to the start position when the lift arrives at the lower charging contact. This
contact is recognized by the system because the polarity of this charging contact is reversed with respect to all other
charging contacts.
Drive system control
Figure 4-12: Principle of the drive motor control system
The electronics on the control board contain a three phase motor control for the three phase brushless dc motor and
is controlled by the microcontroller. The pulse counter receives the pulses from three encoders on the motor axis
and calculates the motor position. The driving signals are sent to the motor driver to give the motor the speed
according the rail data table values.
The microcontroller guards during operation the motor current and the motor voltage. In case of over- or under
current or over- or under voltage the power will be disconnected from the drive motor control and electrically operate
the brake.