Aumov LV Ultramov Varistor Design Guide Page 10 Varistor Design Guide For DC & Automotive Applications

2015 Littelfuse DC Application Varistor Design Guide www.littelfuse.com DC Application Varistor Design Guide Automotive Applications System Protection against Alternator Transients Alternator Voltage Reg. BATT + Airbag ABS Air Condition Wipers Window Motor Vehicle subsystem module transient protection Voltage Reg. ECU Airbag Motor Infotainment Etc. Protected System Alternator Automotive Relay Surge Protection Relay Coil Starter Lights Speaker Etc. Protected System The alternator causes most of the transients in a vehicle's electrical system. Littelfuse automotive MOVs can be connected in a Y or Delta configuration with the winding coil of the alternator to clamp the transients. Vehicles subsystems such as the ECU, airbag, etc. can be damaged by the transient caused when the alternator provides power to the electronics. Littelfuse automotive MOVs can be used as a shunt for the transient surge for the DC power line. Typical relay operation would generate arcing during the switch of the relay contacts, thereby damaging the IC and other sensitive electronic devices. Littelfuse automotive MOVs will absorb the arcing energy released from the magnetic fields of the relay. Automotive MOV Background and Application Examples (continued) 9

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