Research On EMC Optimization Of Low Voltage Direct Current Motor In The Electric Vehicle

There are many high voltage and low voltage electrical and electronic systems in the electric vehicle(EV).Serious issues of electromagnetic interference(EMI)appear when the systems work.EMI will has great effect on electric and electronic equipment.Low voltage direct current motor(LVDC motor)used widely in the EV also has the mentioned issues.Serious EMI influences EMC characteristics of motor and vehicle.For the inadequacy in research on EMC characteristic of LVDC motor,it is regarded as research object in this article.The EMC characteristic and EMC rectification of LVDC motor are major contents in the article.At the beginning of article,it is aimed at introducing EMC research status of EV and its components,resolving three important national standards about EV EMC and analyzing three EMC rectification methods and their principles.Five EMC characteristics are researched by tests,including impedance characteristic,conducted emission characteristic,radiated emission characteristic,transient conducted emission characteristic and coupling characteristic.Specifically,radiated emission is used to research the influence of different test factors on the test results.And a vehicle EMC test is conducted to verify the relationship of radiated emission between the LVDC motor and the vehicle.In the part of EMC rectification,mechanism of ferrite ring about suppression on conducted interference from motor is studied.The influence of quantity and coil turn of ferrite ring on impedance and resonance frequency is researched.Comparison tests is made by wiper motor between grounding points to discuss the influence on radiation emission.Butter-worth filter is applied for suppression on interference current,and its insert loss is improved by some optimization measures.The article shows that structure and working principle of LVDC motor result in intense electromagnetic interference(EMI).The conducted emission and radiated emission from motor have a great effect on radiated emission in vehicle.The EMI will be lower for the increase of inductance and impedance due to ferrite ring,and more ferrite rings in series and more turns in the coil bring about higher and better suppression.Meanwhile,resonance frequency decreases.The conclusion that grounding loop area and grounding loop current are crucial factors to radiated emission is proposed.The decrease of parasitic parameters of Butter-worth filter is used for improvement of suppression on EMI in the circuit.