Testing A Three-Phase Alternator With Permanent Magnet Rotor - Rothewald 10002567 Mode D'emploi

against the positive battery terminal, and the black test probe
against the negative. Read off the value – for a well charged 12 V
battery, the display should now indicate approx. 12.6 V. Then,
depending on the model of bike, increase the engine speed to
around 3000 – 4000 rpm. With a 12 V system, the reading should
now increase to approx. 13.5 to 15.5 V; in this case the alternator
is charging correctly. If, on the other hand, the voltage stays the
same, then there is a fault in the charging circuit. If the voltage
increases beyond the range 13.5 to 15.5 V when the engine speed
is increased, this indicates that the voltage regulator/rectifier is not
limiting the voltage correctly. Measurable short-term voltage peaks
indicate a fault in the rectifier and/or alternator.
6.1.2 | Testing a three-phase alternator with permanent magnet
rotor
Three-phase alternators operate with a permanent magnet rotor
that induces a voltage by turning in the windings of the outer stator.
They run in an oil bath, usually on the crankpin. Faults generally
occur as a result of persistent overheating or overloading of the
regulator.
• Testing the non-rectified charging voltage
Stop the engine and switch the ignition off. Disconnect the plug
on the cable leading from the alternator to the regulator/rectifier.
Insert the red test lead in the VΩmAhFE jack, and the black test
lead in the COM jack on the multimeter. Select the measuring range
up to 200 V AC. Connect two of the alternator's plug contacts
with the test probes. Run the engine at approx. 3000 – 4000 rpm.
Measure the voltage. Switch engine off, connect test probes
in a different contact combination, switch engine on again and
measure etc. If the measurements with all the possible connection
combinations are the same (as a rule, a mid-range motorcycle
alternator delivers approx. 50 – 70 V), the alternator is functioning
correctly. If occasional measurements are significantly below the
others, the alternator is faulty.
• Checking for a short circuit to earth and interturn fault
Stop the engine and switch the ignition off. Insert the red test lead
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