Resolving vehicle EMI/EMC issue without adding any ferrite core ($5 cost saving on each vehicle)

While working as reliability engineer in my earlier career I learned a principle that less the complexity of product design led to more reliability. This principle always makes me to avoid adding more component into design (until it is must).?

Recently received one EV 3-Wheeler which was not meeting the BB RE homologation requirement with respect to ECE R10 standard. The vehicle architecture was simple with Traction Battery, Motor for power train (<60V system) and DC-DC converter which take input supply from traction battery to charger LV battery and supply vehicle EE components.?

Some test iteration on the vehicle was already performed in ALSE chamber and there were two big ferrite cores already connected on the harness of the vehicle to address the Narrowband (NB) Radiated Emission (RE) issue. The two big ferrite cores might be costing for about $2 ~ $3 in total.?

Our work starts here and following approach was taken for root cause analysis:?

1. Scan the vehicle to narrow down the area of emission on the vehicle, this was to identify probable sources of emission (the component which is emitting on the vehicle).?
2. Further narrow down the emission on wiring harness level.?

While scanning the vehicle, following were the observations which guided us to solution:?

(a) For point no. 1 above, Vehicle behavior was not consistent. Sometime the vehicle emissions were suddenly increasing. The reason identified was loose contact, as every time supply of one of LV motor shakes; vehicle emissions were increase drastically. For BB RE vehicle will be in driving condition on dyno led to vibrations. Those vibrations were making the supply wire to shake for the LV motor of vehicle, which was reflected as random BB emissions crossing the limit lines from 30 MHz to 45 MHz.?

(b) BB Emissions was observed near the charging port of the vehicle (around 55 MHz). As those emissions were very close to the limit, hence we had targeted to bring only 2 to 3 dB margin from limit (to avoid adding any extra cost to vehicle).?

(c) BB Emissions was observed near the traction motor controller of the vehicle (around 85 MHz to 95 MHz). These emissions were very close to the limit, hence we had targeted to bring only 2 to 3 dB margin from limit (to avoid adding any extra cost to vehicle).?

(d) While scanning the wiring harness for the components where already 2 big ferrites were added we understood that there were no emissions (which may cross limit) coming from the harness where their ferrites were mounted.?

Solutions provided:?

With a record time of 5 days, we had reached to solutions. For point (a) mentioned above, we had twisted the wire and tie the same close to vehicle chassis to avoid vibrations. For point (b) and (c) proper routing of the wiring harness had helped us to bring 2 to 3 dB margin.?

While performing the final compliance test we could be able to meet both NB and BB requirements without adding a single ferrite core on the vehicle and could save $3 and additional process cost of around $2 on each vehicle.?