ABB ACS 400 User Manual page 118

Code Description
8119 AUTOCHNG LEVEL
Sets the operation limit for the Autochange logic. This parameter can be used to deny Autochange when the
Pump-Fan system is operating near maximum capacity. When the output from PID/PFC control block
exceeds the level set by this parameter, Autochange operation is not possible.
Figure 57 Autochange level.
Autochange operation
The purpose of the Autochange operation is to ensure equal duty time for all the motors. Each motor in the
system will in its turn be connected to the ACS 400 as well as direct on line. Starting order of the motors is
changed when Autochange is done.
To use the Autochange function, an external alternation switchgear is needed. Refer to Appendix B for more
information. When Autochange is used, the interlocks (parameter 8120) must also be taken into use.
The Autochange is performed when the Autochange Interval (parameter 8118) is elapsed from the previous
autochange and the output from PFC is below the level set by this parameter.
Autochange operation is as follows:
1. The speed controlled motor stops. The contactor of the speed controlled motor is switched off.
2. The starting order is changed (the starting order counter steps onward).
3. The contactor of the motor that will be the new speed controlled motor is switched off (if the motor is
running). If other motors are running, they will not be interrupted.
4. The contactor of the new speed controlled motor is switched on. The autochange switchgear connects
this motor to the ACS 400.
5. Time set with parameter 8122
6. Speed controlled motor starts. If a constant speed motor was stopped in Step 3, one more motor is
connected direct on-line by switching on the contactor of that motor. After this step the same number of
motors is running than before the Autochange.
7. Normal PFC operation continues.
As an example, in a three motor system the starting order is changed as follows:
First start: Motor no. 1, motor no. 2, motor no. 3.
Second start: Motor no. 2, motor no. 3, motor no. 1.
Third start: Motor no. 3, motor no. 1, motor no. 2. (etc...)
If some motors in the system are interlocked, the Autochange logic skips them. If all interlocks are active
and no motor can be started, interlock alarm (Alarm 30) is displayed.
Note! The ACS 400 always coasts to stop when autochange is performed.
Note! Autochange can also occur during PID sleep.
Note! When ACS 400 power supply is switched off, the values of the starting order counter and Autochange
Interval counter are stored in the permanent memory. The counters continue from the stored values after
the power supply is switched on again.
108
Output frequency
f
MAX
No aux
motors
Allowed autochange area
8119
PFC START DELAY
1 aux 2 aux
motor motors
100 %
AUTOCHNG LEVEL
is waited.
PID output
ACS 400 User's Manual