Modeling conducting emission transients due to DC motor switching in automotive applications

Conducted emissions are currents that exit a device via its power harness. They are undesirable as they can couple to other devices or cause unwanted radiation. DC motors are common culprits for generating conducted emissions in an automobile, as they generate a large transient current when they are switched on or off. Some of this transient current is introduced onto the common power net of the vehicle.Daimler Chrysler wishes to regulate the conducted emissions within their vehicles. They have self-imposed limits to conducted emissions and methods with which to test them. However, performing individual measurements on conducted emission transients for every DC motor in every vehicle they produce is undesirable. The ability to model unwanted emissions from a DC motor would reduce the need to individually test each motor.This thesis examines conducted emission transients from several DC motors found in automobile applications. The conducted emission transients are measured and examined. The natural frequencies of each motor are determined and with this information the conducted emissions of the motor are modeled. Additionally, using the measured currents and impedances of each motor, a model for worst-case radiated emissions is also created.