Aumov LV Ultramov Varistor Design Guide Page 8 Varistor Design Guide For DC & Automotive Applications

2015 Littelfuse DC Application Varistor Design Guide www.littelfuse.com DC Application Varistor Design Guide Automotive MOV Background and Application Examples Threats on Low Voltage Line 85V Noise Reverse Battery 24V Jump Start 6V Crank 120V Load Dump Norminal 14V Automotive EMC transient requirements from ISO 7637: Pulse 1 Interruption of inductive load - refers to disconnection of the power supply from an inductive load while the device under test (DUT) is in parallel with the inductive load Pulse 2 Interruption of series inductive load - refers to the interruption of current and causes load switching Pulse 3 Switching spikes 3a negative transient burst 3b positive transient burst Refers to the unwanted transients in the switching events Pulse 4 Starter crank - refers battery voltage drop during motor start. This always happens in cold weather Pulse 5 Load dump - refers to the battery being disconnected when it is charged by the alternator. Pulse 6 Ignition coil interruption Pulse 7 Alternator field decay Pulses 1, 2, 3a, 3b, 5, 6, 7 Related to high voltage transient getting into the supply line; Pulse 4 defines minimum battery voltage. Automotive MOV Background and Application Examples 7

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