how to check IR values in alternator winding?
Answer Posted / subash
A. Purpose and Theory
The IR test measures the resistance of the electrical
insulation between the copper conductors and the core of
the stator or the rotor. Ideally this resistance is
infinite, since after all, the purpose of the insulation is
to block current flow between the copper and the core. In
practice, the IR is not infinitely high. Usually, the lower
the insulation resistance, the more likely it is that there
is a problem with the insulation.
PI is a variation of the IR test. PI is the ratio of the IR
measured after voltage has been applied for 10 minutes
(R10) to the IR measured after one minute (R1), i.e.:
PI = R10/R1
A low PI indicates that a winding may be contaminated with
oil, dirt, insects, etc. or soaked with water. In the test,
a relatively high DC voltage is applied between the winding
copper and the stator or rotor core (usually via the
machine frame). The current flowing in the circuit is then
measured
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