28
PN: 81127
Rev 4, 6/2017
3.1.14
14
Timer Display Window
Displays operating time of the device under test. The Time window does not appear until the test is
started by pushing the blue play button.
3.1.15
15
Output Current Amplitude Window
Displays the test current being applied to the device under test. . The Current window does not appear
until the test is started by pushing the blue play button. Pressing or clicking on the eraser in the Current
window will clear the recorded test current and time like a reset button.
3.2
Selection of SPI225 Output Terminals
The Megger Model SPI225 primary injection test set has multiple output terminals to provide a wide range
of current-voltage capabilities. There are three output terminals to choose from: 25 Amp at 70 V, 125 Amp
at 14 V, and 500 Amp at 3.5 V. The terminal with the lowest current rating provides an output with the
highest voltage for testing devices of low current requirements but with higher impedance characteristics.
The highest current rated output terminal provides high current availability for testing devices of high current
requirements of relatively low impedance. Should the current required for the device to be tested exceed
the ability of the lowest tap or the impedance of the device to be tested require more voltage to "push" the
current than is available from the highest current tap, the medium range current tap can be utilized to
provide the current or voltage necessary to perform the desired test.
Should the test current requirement exceed the maximum output capability of the unit, multiple SPI units
can be operated in parallel to multiply the maximum output current, see section 3.3.1. If the load has
significant impedance two or more units (output tap dependent) may be operated in series to multiply the
maximum output voltage “pushing” the test current, see section 3.3.2.
Note that the SPI units are high current test sets and a good supply voltage is required for proper operations.
When possible, avoid the use of any type of power strips and small gauge extension cords. When extension
cords must be used, use only properly rated cords with sufficient current capability. Additionally, when
maximum current capability is required, remember that the SPI can be powered from a 240 AC supply.
This can help to obtain maximum current output from the test set.
3.2.1
Selection of Output Leads
The Megger SPI unit is equipped with output connecting bars and a 125 A output tap for attachment of the
provided high current test leads or other leads suitable for the test application.
The SPI unit comes with appropriate test leads and attachments rated for the output of the unit. There are
two sets of leads provided with the SPI unit. One set are heavy-duty high current leads (AWG 4/0 cables
with lead adapter) that connect to the 500 Amp output tap (Figure 21).
