Other Applications; Parallel Operation In Master-Slave Mode (Ms) - Elektro-Automatik PSI 9000 2U Bedienungsanleitung

3.10

Other applications

3.10.1

Parallel operation in master-slave mode (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, 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.
3.10.1.1 Restrictions
Compared to normal operation of a single device, master-slave operation has some restrictions:
• The MS system reacts differently to alarm situations (see below in 3.10.1.6)
• 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
• Depending on the installed firmware version for the KE and HMI unit, it can occur that not every value related
to the current or power of the MS system is translated to match the nominal values during the master-slave
operation. This applies for manual control, but primarily for remote control when using the command language
SCPI. It means, while you can set the current of a MS system, consisting of 2x PSI 9080-340 and with 680 A
nominal current, to 680 A with the corresponding command, you not be able to do so with other current related
values like "I max, "OCP" or "OCD". For example, if you want to set 500 A for OCP and the device would reject
the value with an error "Upper limit exceeded", it would have to be divided by the number of units before sending
it again. The correct number of unit of the initialised MS system can be read from the master. Since this number
can vary, it is not recommended to use a constant. After the value has been sent successfully, it is transferred
1:1 to the slaves so the resulting current of the MS system will match the desired current.
• A device which was configured as slave has limited operability (only access to MENU possible)
3.10.1.2 Wiring the DC outputs
The DC output of every unit in the parallel operation is simply connected to the next unit using cables with cross
section according to the maximum current and with short as possible length.
3.10.1.3 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!
• In order for the Share bus to work correctly it requires at least to connect all DC minus
outputs of the devices
A max. of 10 units can be connected via Share bus.
3.10.1.4 Wiring and set-up of the 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 115200 Bd
• 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 9080-60 2U
to PSI 9080-60 2U.
• Units at the end of the bus must be terminated (see below)
The master-slave bus (RS485) must not be wired using crossover cables!
EA Elektro-Automatik GmbH
Helmholtzstr. 31-33 • 41747 Viersen
Germany
Fon: +49 2162 / 3785-0
Fax: +49 2162 / 16230
PSI 9000 2U Series
www.elektroautomatik.de
ea1974@elektroautomatik.de
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