Section 7 Electrode mana
ement 42
Current measurement by external toroid (spot weld only)
A toroid (Rogowski coil) is connected around the welding transformer secondary. Most such coils have a
nominal output of 150 mV/kA. The iPAK2 provides a sensitivity parameter which may be adjusted to
provide for absolute matching with an external current meter.
At the nominal 150 mV/kA, iPAK2 will handle signals corresponding to about 50 kA. If the current is
expected to exceed 50 kA then it is necessary to use an attenuator device such as a TAM/1 between
the toroid and iPAK2. The attenuator will have options for x1, x2, x3, x4 etc. The factor selected should
be entered into the iPAK2 so that it is able to calculate the actual current from the (attenuated)
measured current.
In multi-electrode or multi-transformer (cascade) systems it may be difficult to arrange toroids for
multiple secondary circuits. The toroids need to be switched in and out of circuit at the appropriate
moment in the sequence or errors will occur. In these circumstances use the CT measurement method.
The CT method has the advantage of not requiring an external toroid.
Parameter Units Range Description
Max. primary current A 0 - max Limits maximum output
Conversion method points/ratio Method used to convert primary current to secondary current
Turns ratio 1 - 999 The turns ratio of the welding transformer
Point 1 (primary) k
0 - 32.0 The measured value of primary current at a low heat (Ip1)
Point 1 (secondary) k
0 - 500.0 The measured value of secondary current at a low heat (Is1)
Point 2 (primary) kA 0 - 32.0 The measured value of primary current at a high heat (Ip2)
Point 2 (secondary) kA 0 - 500.0 The measured value of secondary current at a high heat (Is2)
Toroid mV/kA 100 - 60000 The sensitivity of the toroid
Toroid factor 1 - 10 The ratio of the external attenuator (1 if no attenuator fitted)
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