Answer / nizam salih

A pole drop test can be done when the generator is in
standstill condition. Provide a ac voltage of 230V to the
rotor terminals of the salient pole machine and measure the
voltage drop in each pole. At least 5A should flow through
the rotor poles. A small current will not provide good
results. Once the voltage drops are recorded calculate the
drop index as follows.
Index = (max. value - min. value)/avearge value *100 %
An index value of less than 5% reprsents the poles are
good.
This is the usual annual test that we carry out in our
hydro generators.
Nizam Salih, Electrical Engineer, Sri Lanka.

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