ISO 7637-2 applies to all 12 volt and 24 volt vehicle's electrical systems regardless of method of propulsion. It designed to ensure that associated electrical systems are able to within stand conducted electrical transients. This standard specifies pulses 1, 2a, 3a, 3b, 4, 5a,and 5b, it references ISO 16750-2 for pulses 4, 5a, and 5b.
Pulse 1: A simulation of transients due to supply disconnection from inductive loads; it applies to a DUT if as used in the vehicle, it remains connected directly in parallel with an inductive load.
Pulse 2a: Simulates transients due to sudden interruption of currents in a device connected in parallel with the DUT due to the inductances of the wiring harness.
Pulse 2b: Simulates transients from DC motors acting as generators after the ignition is switched off.
Pulse 3a/3b: Occurs as the result of switching processes. The characteristics of this pulse are influenced by distributed capacitance and inductance of the wiring harness.