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PSI 9000 3U Series
3.10 Other applications
3.10.1 Parallel operation in master-slave (MS)
Multiple devices of same kind and model can be connected in parallel in order to create a system with higher total
current and hence higher power. For master-slave operation, the units are usually connected with their DC outputs,
their Share bus and their digital master-slave bus.
The master-slave bus is a digital bus which makes the system work as one big unit regarding adjusted values,
actual values and status.
The Share bus is intended to balance the units dynamically in their output voltage, i.e. in CV mode, especially if the
master unit runs a function like sine wave etc. In order for this bus to work correctly, at least the DC minus poles
of all units have to be connected, because DC minus is the reference for the Share bus.
Compared to normal operation of a single device, master-slave operation has some
restrictions
:
•
The MS system reacts differently in alarm situations (see below in
•
Resistance setting and control (CR) is not available. In case, master-slave is not activated in the menu of the
devices, switching to and use of R mode is not blocked, but R mode will not work correctly in a parallel connection
•
Using the Share bus makes the system reacts as dynamically as possible, but it is still not as dynamic as single
unit operation
3.10.1.1 Wiring the DC outputs
The DC output of every unit in the parallel operation is connected with correct polarity to the next unit, using cables
with cross section according to the maximum current and with short as possible length.
3.10.1.2 Wiring the Share bus
The Share bus is wired from unit to unit with an ideally twisted pair of cables with non-critical cross section. We
recommend to use 0.5 mm² to 1.0 mm².
• The Share bus is poled. Take care for correct polarity of the wiring!
• Using the Share bus requires to (at least) connect all DC minus outputs of the de-
vice, as reference for the bus to work correctly
A max. of 10 units can be connected via Share bus.
3.10.1.3 Wiring and set-up of the digital master-slave bus
The master-slave connectors are built-in and can be connected via network cables (≥CAT3, patch cable). After
this, MS can be configured manually (recommended) or by remote control. The following applies:
•
Type of connection: RS485 with 115200Bd
•
A maximum 10 units can be connected via the bus: 1 master and up to 9 slaves.
•
Only devices of same kind, i.e. power supply to power supply, and of the same model, such as PSI 9080-170
3U to PSI 9080-170 3U.
•
Units at the end of the bus must be terminated (see below)
The master-slave bus (RS485) must not be wired using crossover cables!
Later operation of the MS system implies:
•
The master unit displays, or makes available to be read by the remote controller, the sum of the actual values
of all the units
•
The ranges for setting the values, adjustment limits, protections (OVP etc.) and user events (UVD etc.) of the
master are adapted to the total number of units. Thus, if e.g. 5 units each with a power of 5 kW are connected
together to a 25 kW system, then the master can be set in the range 0...25 kW.
