Short Circuit Jumpers; Temperature Correction; Short Circuit Impedance Deviation - Raytech mini-ATOS Instruction Manual

4.5.2 Short Circuit Jumpers

The mini-ATOS automatically short-circuits the windings on the other side, but it is strongly
recommended to manually short them using low resistance jumpers. The reason for this is that the
resistance of the mini-ATOS test cable is much higher compared to the resistance of the windings,
which can affect the measurement. Special jumper cables designed for this purpose can be
ordered as optional accessories from Raytech.

4.5.3 Temperature Correction

The winding temperature has effect on the ac resistance value and so it can be corrected to a
reference temperature. The method is exactly like the DC resistance temperature correction. For
more information, please refer to chapter 4.2.2.
The winding temperature has no effect on the leakage reactance, however it has effect on the
short circuit impedance, because the ac resistance is the real part of the short circuit impedance.

4.5.4 Short circuit impedance deviation

For a 3-phase test object, the short circuit impedance values of each phase are supposed to be
almost the same. Hence, it is possible to measure a deviation value from the average value for
each phase as follows:
The calculated deviations can be compared to a maximum deviation limit value to find out if the
result is passed or failed.
Please note that if the temperature of phases is not the same during the short circuit impedance
measurements, the deviation values may be higher. In this case, it is better to calculate the
deviation values of the temperature-corrected values.
90297-0.24 Instruction Manual mini-ATOS
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