© EA Elektro-Automatik in 2022, this information is subject to change without notice
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3.10.1.7 Operating the master-slave system
After successful configuration and initialization of the master and slave units, they will show their status in the in the status
area of their displays. The master would show
MS mode: Master
while the slave(s) would show
MS mode: Slave
plus
Remote:
Master-slave
, as long they are in remote control from the master.
From now on the slaves can no longer be controlled manually or remotely, neither via the analog nor via digital interfaces.
They can, if needed, be monitored via these interfaces by reading actual values and status.
The display on the master unit will reconfigure after initialization and all set values are reset. The master now displays the set
and actual values of the total system. Depending on the number of units, the adjustable current and power range will multiply,
while the resistance range will decrease. Then following applies:
•
The system, represented by the master, can be treated like a standalone unit
•
The master shares the set values etc. across the slaves and controls them
•
The master is remotely controllable via the analog or digital interfaces
•
All settings for the set values U,I, P and R on the master, plus also all related values from supervision, limits etc. should be
adapted to the new total values
•
All initialized slaves will reset any limits (U
Min
, I
Max
etc.), supervision thresholds (OVP, OPP etc.) to default values, so these
don’t interfere the control by the master. As soon as these values are modified on the master, they are transferred 1:1 to
the slaves. Later, during operation, it might occur that a slave causes an alarm earlier than the master, due to imbalanced
current or slightly faster reaction.
In order to easily restore all these settings to what was configured before activating MS operation, it’s
recommended to make use of the user profiles (see “3.9. Loading and saving user profiles“
)
•
If one or more slaves report a device alarm, it will be signaled on the master and must be acknowledged also there. so that
the slave(s) can continue their operation. Since an alarm causes the DC outputs to be switched off and can only reinstate
the on/off condition automatically after PF or OT alarms, where the reaction to the alarms is configurable, action from an
operator or a remote control software may become necessary.
•
Loss of connection to any slave will result in shutdown of all DC outputs as a safety measure and the master will report
this situation in the display with a pop-up telling “Master-slave security mode”. Then the MS system has to be re-initialized,
either with or without prior re-establishment of the connection to the disconnected unit(s).
•
All units, even the slaves, can be externally shut down on their DC outputs using the pin REM-SB of the analog interface.
This can be used as some kind of “emergency off”, here usually a contact (maker or breaker) is wired to this pin on all units
in parallel.
3.10.1.8 Alarms and other problem situations
Master-slave operation, due to the connection of multiple units and their interaction, can cause additional problem situations
which do not occur when operating individual units. For such occurrences the following regulations have been defined:
•
Generally, if the master loses connection to any slave, it will generate an MSP (master-slave protection) alarm, pop up a
message on the screen and switch off its DC output. The slaves will fall back to single operation mode, but also switch off
their DC output. The MSP alarm can be deleted by either initializing the master-slave system again. This can be done either
in the MSP alarm pop-up screen or in the MENU of the master or via remote control. Alternatively, the alarm is also cleared
by deactivating master-slave on the master unit
•
If one or more slave units are cut from AC supply (power switch, blackout, supply undervoltage) and come back later, they’re
not automatically initialized and included again in the MS system. Then the init has to be repeated.
•
If the master unit is cut from AC supply (power switch, blackout) and comes back later, the unit will automatically initialize
the MS system again, finding and integrating all active slaves. In this case, MS can be restored automatically.
•
If multiple units are defined as master the master-slave system can’t be initialized
In situations where one or multiple units generate a device alarm like OVP etc. following applies:
•
Any alarm of a slave is indicated on the slave’s display and on the master’s display
•
If multiple alarms happen simultaneously, the master only indicates the most recent one. In this case, the particular alarms
can be read from the slave units displays or via digital interface during remote control or remote supervision.
•
All units in the MS system supervise their own values regarding overvoltage, overcurrent and overpower and in case of
alarm they report the alarm to the master. In situations where the current is probably not balanced between the units, it can
occur that one unit generates an OCP alarm though the global OCP limit of the MS system was not reached. The same can
occur with the OPP alarm.
