Suppressing EMI in a DC/DC converter

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JamesNZ
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Does anyone have any quick fix solutions or detailed solutions to suppress EMI emissions coming from a DC/DC converter (transformer) on a 48V 1500W e-scooter?.

Can you buy suppression systems? I'm trying to engineer a new converter (not that I am an engineer) so that my e-scooter passes EC/97/24 European radiation emission Standards. So far I have made some modifications to the converter eg. Feeding the current into the casing using 3 100nF capacitors and trying to seal the current in the converter casing but have had no luck. Not sure how they do it in big brand e-bikes like Vectrix?

Maybe someone has some comments or knows about the vectrix converters because it's out of my league! :? Maybe someone knows where the converters are are made so I could get one sent to new zealand and have a look?

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ArcticFox
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Re: Suppressing EMI in a DC/DC converter

Try using inductors along with the capacitors.

Capacitors are for filtering higher frequencies, inductors are for low. Also try changing the values of each to adjust the filtering to your specific issue. I'm sure there's some math that could figure it out better.

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JamesNZ
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Re: Suppressing EMI in a DC/DC converter

Thanks very much for the tips.
Is there any test equipment I could buy to test the DCDC converter for EMI in isolation rather than testing the whole scooter in an expensive radiation facility??

Mik
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Re: Suppressing EMI in a DC/DC converter

Do you want to export scooters from NZ to Europe?

Mr. Mik

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JamesNZ
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Re: Suppressing EMI in a DC/DC converter

Not at this stage or in the future realistically.

Mik
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Re: Suppressing EMI in a DC/DC converter

I am just wondering why you want to meet the European emission standards.

Mr. Mik

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JamesNZ
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Re: Suppressing EMI in a DC/DC converter

No worries. Primarily because to me that is an EMI standard that I can use as a yardstick on safety so if our scooter is operated then its not going to cause serious health problems!

ArcticFox
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Re: Suppressing EMI in a DC/DC converter

I didn't know EMI caused any health problems since the cellphone scare of 1988.

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reikiman
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Re: Suppressing EMI in a DC/DC converter

I don't know the answer to your question ..but..

Last week I was at a conference for online community professionals. One of the attendees works for Consumer Union (the publishers of Consumer Reports) running their online community. I'd mentioned I work with electric vehicles and that prompted many people to talk with me, she was one of them. Turns out a few people are asking about the effects of the electrical field in hybrid cars...

Okay, a new gizmo, it raises the fear factor in people.. it's "new" so therefore it must be strange and therefore it must have lurking dangers?

(never mind that electric vehicles date to the 1800's and hybrid electric vehicles date to the 1910's and earlier and that most diesel trains are hybrids...)

FWIW I'm very sensitive to electric fields. The first time I used a cell phone it felt like this giant fuzzball was next to my ear, the shape of the phone plus with an extension where the antenna stuck out. Some CRT computer monitors I've used felt like a blast furnace. etc.. I'm one who thinks that electrical signals can cause negative health effects and am glad the Europeans are more proactive about these things. For example many parts of our bodies (the nervous system etc) use electrical signals and are sensitive to electrical signals. What if there are ambient electrical signals, what effect will those have on the signals our bodies do innately?

Anyway...

It appears to me there are two aspects to how an electrical signal will affect our bodies: a) Power of the electrical signal, and b) the frequencies

For example I've noticed that as cell phone power levels decrease that I have less notice of the electrical fields of cell phones.

Most of the EV's we play with on this forum are DC powered and while the power level is pretty high it's just a DC signal. No frequency. With my electrical sensitivity I have a hard time noticing the power in e.g. my Lectra motorcycle, which runs at 6kwatts or a heck of a lot more power than the cell phone runs.

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Mik
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Re: Suppressing EMI in a DC/DC converter

reikiman wrote:

Most of the EV's we play with on this forum are DC powered and while the power level is pretty high it's just a DC signal. No frequency. With my electrical sensitivity I have a hard time noticing the power in e.g. my Lectra motorcycle, which runs at 6kwatts or a heck of a lot more power than the cell phone runs.

The electric field strength reduces as an inverse function of the distance.
Also known as an inverse square law.

Therefore: Small increases in the distance to the source lead to large reductions in received radiation.

The electric field surrounding a point charge is given by Coulomb's law: http://en.wikipedia.org/wiki/Coulomb%27s_law

Mr. Mik

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JamesNZ
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Re: Suppressing EMI in a DC/DC converter

Does anyone know if using a smaller power motor would reduce the overall EMI? At the moment I use a 1500W motor, would changing to an 800W motor reduce the EMI?

frodus
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Re: Suppressing EMI in a DC/DC converter

you want to reduce EMI? Put it in a metal enclosure. It will shield most of that stuff from coming out. Ever take apart stuff and small metal enclosures soldered to the board around the components that give off or are sensitive to EMI?

You want to reduce noise? look at the spec sheet on the converter, and see if they recoment putting capacitors and inductors on the output.

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Mik
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Re: Suppressing EMI in a DC/DC converter

JamesNZ wrote:

Does anyone know if using a smaller power motor would reduce the overall EMI? At the moment I use a 1500W motor, would changing to an 800W motor reduce the EMI?

Size does not matter anywhere near as much as shielding and distance.

Small electric motors / controllers, like electric shavers or toys, can cause a lot of emissions, disturbing radio and TV reception.

An AM radio could maybe be used as a crude meter to measure the effectiveness of your shielding.

Mr. Mik

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JamesNZ
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Re: Suppressing EMI in a DC/DC converter

Thanks Mr Mik, I like your ingenuity with the radio.
How about if a 60V battery was used instead of a 48V battery would that likely increase the EMI? Would the DC/DC converter have to be changed for a 60V battery?
Cheers

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