Modelling of conducted RFI emissions from 5 phase unipolar brushless DC motors for automotive engine cooling applications.

摘要

In the automotive environment, conventional electromechanical parts are being replaced with, or are being controlled by electronic devices. As the number of electronic devices in automobiles increases, the focus on electromagnetic compatibility (EMC) has become greater, particularly where customer safety and comfort is a concern.; Traditionally, the issue of EMC has been addressed towards the end of the design cycle with a focus on “brute force” trial and error approaches to EMC design. Design cycles are becoming shorter, EMC specifications are becoming more stringent, and concurrent engineering is a rule in product design. Consequently, EMC solutions must be considered at the beginning of the design cycle.; In the realm of electric motors and drives for automotive applications, the supply of low frequency, low fidelity, virtual models has already been mandated by a number of North American and European automobile manufacturers. If present trends continue, the need for high frequency virtual models is also anticipated. This need will be driven by reduced design cycle times in addition to excessive test times and costs for EMC testing.; In this thesis, conducted RFI emissions from a 400 W, 5 phase, unipolar, brushless DC motor used in an automotive engine cooling application are simulated in the frequency range from 150 kHz to 30 MHz. A measured model approach was used, whereby the machine was characterised through empirical measurement, and the lumped parameter values placed in a SPICE model along with the simulation model for the motor drive. By using a virtual spectrum analyser implemented in MATLAB, the conducted RFI spectrum of the motor is characterised through a frequency domain analysis of the output voltages from the line impedance stabilisation network (LISN) in the SPICE model.; In order to validate the simulation model, two motor winding types are simulated as well as an inverter with additional conducted RFI suppression elements. A sensitivity analysis of the motor model is performed to examine the effects of changes in various motor parameters on conducted emissions. A simplification of the simulation model is also presented.