ABB 800xA Operation page 202

Transfer from Manual to Automatic
Switching from Manual to Auto can be made bumpless by using the following
techniques:
Transfers In A Loop With Ratio Or Bias Balancing
The Balance Mode field on the FCM templet is used to specify either ratio or bias
automatic adjustment by the system so the Auto Output Value of the controller is
equal to the Manual Output Value.
Transfers In A Loop With Output Tracking
The output of a PID FCM supplying the input for the Auto/Manual Controller FCM
can be configured to track the TRAK-VAR parameter of the Auto/Manual
Controller FCM.
Transfers In A Loop With Automatic Reset Balancing
When the control algorithm has reset (integral) response, transfers from automatic
to manual and from manual to automatic are always bumpless. After switching from
manual to automatic, the process variable is under automatic control in response to
the active setpoint, either local or remote.
If the control loop is configured for local setpoint tracking, the local setpoint tracks
the process value when the loop is in manual. The process is always at the local
setpoint when a transfer to automatic is made, regardless of setpoint limits
If the control loop does not have local setpoint tracking, the local setpoint and the
process variable may not be at the same value at the time of a transfer from manual
to automatic. The transfer is still bumpless, but immediately after the transfer the
process ramps toward the local setpoint value at the reset rate.
Transfers In A Loop With Manual Reset
If the control loop does not have automatic reset (integral) response, any
setpoint/process offset at the time of a transfer from manual to automatic is
maintained. If the loop is configured to provide procedureless manual reset, the
manual reset value required to eliminate the offset is automatically calculated while
the loop is in manual, and this calculated value is used to remove the offset
following a transfer to automatic.
202
Section 8 Operation Examples
3BUR002418-600 A