Hi,
Since everything works on my E-Porsche, I decided it's time to play with pesky EMI. I get really cranky if I can't hear NPR, news, Terry Grose, Car Talk, Garrison Kheilor, Wait,wait don't tell me etc., and I live out in the sticks (Blue Ridge Mountains) between the Appalachian Trail & Blue-Ridge Parkway. So EMI must be vertually non-existant (like when the EV is off).
I ran the main controller cables down the left side metal enclosed channel of the 914 (74') E-Porsche and all control signals down the right side and through the center tunnel as the original conversion. I still had trouble picking up the weaker NPR talk channel with terry gross at lunch (that I listen to while getting E-parts around town). By turning off each DC converter in sequence I could identify the worst culprits (while on the weak station). (I have 2 dc-dc converters for reliability, one set to 14V and a backup to 13.8V). I found that the original DC converter VP-12124 that I designed for www.valcom.com had proper inpu and output PI filters but the back up Lambda didn't. I put a standard pi-filter on from www.lcr-inc.com where the HV line comes in (a 2mH balun with .22uf X-cap & twin .0047uf Y-caps to RF frame ground reference). I also put a high current 1Mh 12A balun choke on the output for common mode RF. This got rid of the EMI from the DC converter.
There was still EMI present, I could tell while the radio was on and the ignition key was switched on & off. It was my dash display uP controlled battery charger and run monitor (displays volts, RPM's Temp etc.) This thing has a scanning display and an internal oscillating dc-dc converter *and* is mounted in the dash next to the radio, oops. Since it's main function is for charge control, rather than choke-treat the umpteen wires coming out of it for conducted EMI and a shielded box for radiated, I decided to just put a "NPR switch" on it to turn it off while I'm listening to the FM. Now I can't tell when the car is on or not, I get the *same* good reception (and no interference from the traction control with a 200uH choke in series and channeled cables). That's right, no difference whether the ignition key is on or off, same reception on faint stations. (Don't listen to AM though but it appears ok).
Have a renewable energy day,
Mark in Roanoke, VA
_________________________________________________________________
Capture your memories in an online journal!
http://www.reallivemoms.com?ocid=TXT_TAGHM&loc=us
_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
Since everything works on my E-Porsche, I decided it's time to play with pesky EMI. I get really cranky if I can't hear NPR, news, Terry Grose, Car Talk, Garrison Kheilor, Wait,wait don't tell me etc., and I live out in the sticks (Blue Ridge Mountains) between the Appalachian Trail & Blue-Ridge Parkway. So EMI must be vertually non-existant (like when the EV is off).
I ran the main controller cables down the left side metal enclosed channel of the 914 (74') E-Porsche and all control signals down the right side and through the center tunnel as the original conversion. I still had trouble picking up the weaker NPR talk channel with terry gross at lunch (that I listen to while getting E-parts around town). By turning off each DC converter in sequence I could identify the worst culprits (while on the weak station). (I have 2 dc-dc converters for reliability, one set to 14V and a backup to 13.8V). I found that the original DC converter VP-12124 that I designed for www.valcom.com had proper inpu and output PI filters but the back up Lambda didn't. I put a standard pi-filter on from www.lcr-inc.com where the HV line comes in (a 2mH balun with .22uf X-cap & twin .0047uf Y-caps to RF frame ground reference). I also put a high current 1Mh 12A balun choke on the output for common mode RF. This got rid of the EMI from the DC converter.
There was still EMI present, I could tell while the radio was on and the ignition key was switched on & off. It was my dash display uP controlled battery charger and run monitor (displays volts, RPM's Temp etc.) This thing has a scanning display and an internal oscillating dc-dc converter *and* is mounted in the dash next to the radio, oops. Since it's main function is for charge control, rather than choke-treat the umpteen wires coming out of it for conducted EMI and a shielded box for radiated, I decided to just put a "NPR switch" on it to turn it off while I'm listening to the FM. Now I can't tell when the car is on or not, I get the *same* good reception (and no interference from the traction control with a 200uH choke in series and channeled cables). That's right, no difference whether the ignition key is on or off, same reception on faint stations. (Don't listen to AM though but it appears ok).
Have a renewable energy day,
Mark in Roanoke, VA
_________________________________________________________________
Capture your memories in an online journal!
http://www.reallivemoms.com?ocid=TXT_TAGHM&loc=us
_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
