Section 7 Electrode mana
ement 41
Current calibration
Current is measured by one of two methods:
1. Primary current is measured by the iPAK2 built-in CT.
2. Secondary current can be measured via an externally connected Toroid (spot weld modes
only).
The method is selected by the Configuration parameter Measure (Section 12 Configuration).
Maximum Primary Current
The inverter chassis has a maximum output current specification dependant on the inverter size. The
iPAK2 detects this value on power-up and sets it as an absolute maximum. The output current can be
set below this maximum value. It is important to do this before attempting any of the following calibration
procedures (Section 12 Configuration).
Current measurement by built-in CT
In order to display secondary current, there are two methods provided for conversion:
1. Turns ratio: The turns ratio may be obtained from the welding transformer data. The displayed
secondary current will be the measured primary current multiplied by this value. This method
does not allow for losses in the transformer but will provide reasonable accuracy.
2. Points 1&2: This is the more accurate method and also calibrates the iPAK2 to match an
external current meter. Two test welds establish the relationship between primary current (as
measured by the CT) and secondary current measured using the external meter as follows:
Initially, select the turns-ratio method and set the turn ratio to 1:1 so that the iPAK2
measures and displays primary current.
Produce a short circuit weld at a low heat in CCu mode and note the primary current (Ip1)
from the iPAK2 and the corresponding secondary current (Is1) using an external weld
current meter.
Repeat the short circuit weld at a higher heat and note again the primary current (Ip2) and
secondary current (Is2).
Now select the Points 1&2 method and enter the four measurements (Ip1, Is1 and Ip2,
Is2).
The iPAK2 uses the characteristic to calculate the secondary current from the measured primary
current.
I
p
I
s1
I
s
I
p2
I
p1
I
s2
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