To measure sustained output, the alternator is run at 3,000 RPMs for 60 minutes with a plexiglass shield covering the units. Testing shows that after 60 minutes in these conditions, alternators reach their maximum operating temperature, or the conditions under which the unit will produce the least output.

It is under these harsh conditions where we measure the “hot” output of the units at various RPMs. The complete power curve is shown above.

Note: The “hot” conditions are much less favorable than the conditions typically used in the industry. The temperature of the stator during our “hot” test was 305 °F. Incumbents measure the power curve at an ambient temperature of 140 °F. “Cold” testing was done at 71° F.