31
PN: 81127
Rev 4, 6/2017
Where more current is required than one unit can provide, multiple units may be operated in parallel, see
section 3.3.1 for parallel operation. Where more compliance voltage is required due to load impedance
two units may be operated in series, see section 3.3.2.
3.3.1
Parallel Operation
Each SPI current output tap is capable of providing a full rated output; see the appropriate output terminal
ratings. For example - the SPI225 using the 500 Amp output tap can provide a maximum of 500 Amps
for 30 minutes on followed by 30 minutes off, and up to 2000 Amps for 7 seconds on followed by 2
minutes off. If more than 2000 amps is required, two or more units may be connected in parallel to
provide 1000 Amperes each for 30 minutes (with 2 each SPI225 units in parallel), or up to 8,000 amperes
for 7 seconds (4 each SPI225 units in parallel).
NOTES:
1. Parallel or series operation
of SPI’s can only be performed using the 500 amp tap.
2. Each unit should be supplied power via separate circuits with a common phase angle (do NOT
use 180 degrees out of phase circuits or 120 degrees out of phase circuits from a 3-phase
source).
3. The output leads from paralleled SPI
’s should run from each SPI directly to the input terminals of
the device under test (this provides for maximum current capability).
4. It is suggested that the output cables from
each of the SPI’s outputs be twisted to help minimize
the inductive reactance and obtain maximum current (this is especially helpful with longer cables).
Note: When operating multiple SPI units in parallel or series they should not share the same power
circuit. Each unit should be powered from independent circuits of the same phase angle with appropriate
current ratings. Do NOT use out of phase circuits to power parallel/series connected SPI units.
3.3.1.1
Two SPI Units in Parallel
To assist in multiple unit operations the SPI units may be stacked on top of each other. Use the following
guidelines to parallel the 500 Amp current channels of two units:
1. Stack the Master SPI unit on top of the Slave SPI unit. Connect an Ethernet cable from the
Master Unit Ethernet port labeled OUT to the Slave unit Ethernet port labeled IN.
2. Connect the high current test cables to the 500 Amp Output Terminals of each SPI unit and then
directly to the device under test (paralleling the cables directly at the DUT input terminals). Using
cables from both SPI units to the device under test helps to provide the maximum current
capacity. It is not recommended to parallel the two SPI units directly at the output tap terminals
and use one set of leads to the device under test.
3. Connect the STVI (or PC) to the Master unit STVI port (or the IN port for the pc). When the
Select Number of Slave Units menu appears press or click on 1.
4. Power up the SPI units within 1 to 2 seconds of each other. The boot-up process will detect that
there are multiple SPI units in a Master/slave configuration.
5. When the Select a Tap window appears, select the 500 Amp tap. The test screen will now
appear.
6. Observe the Connection icon in the upper left hand corner of the screen. You will note the
number 1 appears in the Connections icon indicating that you now have control of the Master and
1 slave unit.
7. The STVI software, knowing there are two SPI units, will automatically divide the current equally
between the two current output terminals. When setting an output, simply enter the value of the
desired output current. For example, for an output of 2000 Amperes, enter 2000, and with 2 SPI
500 Amp output terminals in parallel each unit will be providing 1000 Amperes.
8. See Simple Manual Timing Test for step by step operation.