Division 4 Measuring the torque and calculating the efficiency of the alternator

The tests are to be carried out in accordance with the ISO 8854:2012.

The load is to be installed at 50 % of the current which is guaranteed by the alternator at 25 °C and a rotor speed of 6 000 rpm, e.g. if the alternator is a 180 A class alternator (at 25 °C and 6 000 rpm), the load is installed at 90 A.

For each speed the voltage and the output current of the alternator are to be kept constant, the voltage at 14,3 V and the current for a 180 A-alternator at 90 A, i.e. for each speed the torque is to be measured by means of the test bench (see figure 1) and the efficiency is to be calculated by means of formula (2).

This test is to provide the efficiencies of the alternator at 4 different speeds in revolutions per minute (rpm):

• At a speed of 1 800 rpm;

• At a speed of 3 000 rpm;

• At a speed of 6 000 rpm;

• At a speed of 10 000 rpm.

The average efficiency of the alternator is to be calculated by means of formula (1).