AAT circuit for sectional bus backup power a

For wiring with two independent power supplies and single busbar segments as mutual backups, the backup power automatic input device (AAT)
should be installed on the segmented busbar circuit breaker , and its circuit is shown in Figure 14-145. This circuit uses a DC operating power supply, and the starting method
adopts a time-limited low-voltage start.
    In the figure, the control switch SAi is used to operate the circuit breaker . The selector switch SAz is used to switch the AAT device, and
the contacts in the dotted box represent those from the control loop.
    When the load current is low, adjust the potentiometer RP to make the relay KA reliably close.