33
PN: 81127
Rev 4, 6/2017
3.3.2
Series Operation
Up to four SPI units (500 Amp tap) may be connected in series in order to increase the available
compliance voltage for high impedance test applications. The series connection should be used only
when the parallel connection does not have sufficient voltage to "push" the desired test current through
the test leads and the device under test. To series the current channels of two units, perform the
following:
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. Use the short high-current cable to interconnect the COMMON of the top unit to the 500 A output
terminal of the lower unit together. Connect current output to the device under test as shown in
the following figure (Figure 25) using properly rated output test leads. If using test leads other
than those supplied by Megger insure that the wire has sufficient size to carry the test current.
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. For series operation, the user will need to access the Configuration Screen
and use the
Ld Connection icon to select the Series operation
icon (see section 2.3.1.12).
8. The STVI software, knowing there are two SPI units in series, will automatically supply the
requested current to both units. Simply enter the value of the desired output current.
9. See Simple Manual Timing Test for step by step operation.
Use the short high current lead to connect the COMMON of the top unit to the 500 A output terminal of
the lower unit together (see Figure 25). Connect the current output of the top (Master) unit to the device
under test and the return to the COMMON of the bottom (slave) unit using properly rated output test
leads. If using test leads other than those supplied by Megger insure that the cable is of a sufficient size
to carry the test current.
NOTES:
1.
Up to four SPI units may be connected in series. Do not attempt to series connect more than four
SPI units.
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.
Only the 500 Amp tap can be used for SPI units in a series connection.
