Electromagnetic Frequencies in the Prius.

OMG not another threat about EMF's in a Hybrid vehicle causing harm to people. I remember reading a thread years about it in the Honda Insight forum. It was proved to be all talk and nothing to really worry about, yet the nut cases continued popping off about it.

For the record, EMF stands for Electro Magnetic Field.

 

<div class='quotetop'>QUOTE(Ron Howell @ Oct 27 2007, 10:33 PM) [snapback]531455[/snapback]</div>

Somebody please correct me if I'm off base here, but aren't all the electrical components in the rear of the Prius DC, not AC? If so, DC components don't really radiate much in the way of EMF. That would require AC. (Magnetic field are generated by rapidly changing voltages, and you only get that in AC current.)
Most of the AC components are under the hood, like the buck-boost converters, DC- to DC converters, ETC. I'd expect more EMF coming off the speakers than the battery pack.

Anybody got any hard data on this?

 

I have a mechanical watch, which would easily become magnetised and run poorly under such circumstances. I'll letchya know if it starts acting squirrely. So far, nothing. Runs like a top.

 

<div class='quotetop'>QUOTE(fwellers @ Oct 28 2007, 08:00 PM) [snapback]531523[/snapback]</div>

One would hope it runs like a watch. (sorry, can't help it.)

 

<div class='quotetop'>QUOTE(narf @ Oct 28 2007, 03:02 AM) [snapback]531503[/snapback]</div>

Okay, I'll correct you. The magnetic field around a DC carrying conductor is just a big as the one around an AC carrying conductor, as long as the currents are equivalent. Now that I have corrected you, let me also state that your general thoughts have some truth to them. AC currents will induce voltages in nearby conductors since the AC makes a time-varying magnetic field. DC currents will only induce voltages in nearby conductors when the DC current varies, which is a small effect compared to the continuously varying field of AC.

Induced voltages and currents are only one of the health risks associated with magnetic fields. The static effects of a strong field are worrisome because of ion migration and related effects, plus a person moving in a static field produces a time varying effect: turn you head and it will induce voltages and currents. In high field magnets you see flashes when you turn your head, from the voltages induced into your nerves. Tell me that's not scary!

Now that we have talked about all of the scary stuff, let me say categorically that I am not worried about the fields in the Prius even in the slightest. These are vary low voltages, as compared to transmission lines, and the amount of wire is minimal, plus you have shielding effects from the steel. I wouldn't worry about it.

As for an earlier poster who thought EMF was Electro Motive Force, that is correct. Engineers and physicists refer to a voltage source as a seat of EMF, which is why we use the symbol E for voltage when it is being supplied by a source, such as a battery. We use V for voltage when the voltage is induced by current flow or something similar. EMF can also be Electro Magnetic Field. There are too many acronyms and not enough letters, so even after borrowing from the Greeks, Romans, and Hebrews, many of the acronyms are over-loaded.

Tom

 

Lemme ask the OP this: do you live somewhere that's wired for AC
power? If so, you've got way more to worry about there.
.
What amuses me no end is some people hollering about EMFs and
spending way too much gummint money on "studies", and then wearing
magnetic bracelets to "cure" arthritis or CTS. Our gullibility knows
no bounds, does it...
.
I'm even aware of some intelligent, scientific-thinking people who
have been taken in by this notion of magnets as an energy source,
from some misreading of old Tesla papers. Sorry, they're not
an energy source until you put work into moving them and keep it
up, and I'll believe otherwise when I see it in front of me.
.
_H*

 

<div class='quotetop'>QUOTE(patsparks @ Oct 28 2007, 07:43 AM) [snapback]531526[/snapback]</div>

Actually, we watch freaks pay some hefty $$ so they hopefully run as well as a $10 timex quartz.

Go figure.



<div class='quotetop'>QUOTE(qbee42 @ Oct 28 2007, 09:46 AM) [snapback]531534[/snapback]</div>

I think my Double-E detector is going off.

 

<div class='quotetop'>QUOTE(Ron Howell @ Oct 27 2007, 11:33 PM) [snapback]531455[/snapback]</div>

Here's the thread you're referring to, with some of the latest measurements.

http://priuschat.com/index.php?showtopic=39325&st=20

 

Hi Ron,

Well, the higher the voltage the power transmission line, the less the magnetic field, for the same power transmitted. 500 KV is not a common power line. Around my town there is a 138 KV loop. You will only see the big 500 KV lines out between cities. And these are dramatically larger than what is commonly seen in an urban enviorment, like down the side of a road. And making the measurement requires knowing the power being tranmitted at the time too. So a deceptive practitioner would just wait till midnight and then say - "see how much lower the field is under the power line that the Prius!".

So, the point is, that finding a 500 KV line and measuring the magnetic field under it could be construed as deceptive or incompetent. As the whole purpose of going to such high voltages is to reduced the current in the conductors which just happens to reduce the magnetic fields around the conductors. And such a high tension wire, will be much more elevated above the ground as well. Again something that will reduce the ground level magnetic field.

The comparison of high tension line magnetic fields to those in the Prius smells of a stunt to me.

What should be measured in and around such high tension wires is the electrical field strength. And I would venture to say it would be off-the-chart in comparison to a Prius. One can hear the crackling on a damp day due to the electrical field under such high tension wires. A measured quantitiy of a high tension power transmission line being so much more than the Prius, is not nearly as impressive. And rightfully so, as the Prius is a 50 KW electrical system, and these transmission lines are capable of 100's of MegaWatts, or 2000 times as much power.





Oh, BTW, the Earth's magnetic field is on the order of 300 (equator) to 600 (magnetic pole) milli Gauss. Here is a link: http://en.wikipedia.org/wiki/Earth's_magnetic_field .

 

<div class='quotetop'>QUOTE(qbee42 @ Oct 28 2007, 08:46 AM) [snapback]531534[/snapback]</div>

NEAT! Next time I'm in an MRI machine, I'll run the experiment! This sounds like fun.

Bob Wilson

 

<div class='quotetop'>QUOTE(bwilson4web @ Oct 28 2007, 01:18 PM) [snapback]531577[/snapback]</div>

BTW Bob,

100 mGauss in a Prius is .1 microTesla (1e-7). A typical MRI machine is 3 Tesla (64 MHz resonance), with plans for 5 T in process.

 

Tom,
Thanks, I stand (or sit actually) corrected. On a related not, I'venever heard of anyone who was worried about the effects of a static megnetic field such as those generated by DC currents. Can they cause the same sorts of heating and other effects that AC induced EMF can?

 

A microwave oven would essentially boil the water in your head, specifically the eyes and the brain. Not recommended.

 

<div class='quotetop'>QUOTE(narf @ Oct 28 2007, 01:28 PM) [snapback]531593[/snapback]</div>

No, they do not cause heating because the field is not time varying. High strength static fields can cause ion migration, and will cause polarization of any free charge, but we are talking about very high fields for this to be an issue.

Tom

 

<div class='quotetop'>QUOTE(bwilson4web @ Oct 28 2007, 12:18 PM) [snapback]531577[/snapback]</div>

We were seeing that effect in 4 T magnets. At the time I was the head of an MRI engineering group, and we were running our high field magnets at 1.5 T. Higher fields increase the signal to noise ratio, but you have to start worrying about neurological effects.

You know what's really fun to do inside of an MRI magnet? Take a coin, preferably a big coin like a quarter or half dollar, and stand it on edge. When you let go, it will fall over like it is in molasses. The metal in the coin is cutting through the magnetic field as the coin moves, inducing an eddy current. The eddy current produces a magnetic field which opposes the the magnetic field in the magnet, which resists the tendency of the coin to fall over. If the coin were made of a superconducting material, it would never fall over, even if placed at an angle. Since it isn't a superconductor, some of the energy is converted to heat, and therefor the resisting magnetic field is a little too small to completely resist the pull of gravity. The coin sloooowly falls over as all of its potential energy is converted to heat.

For the person who mentioned boiling your head in a microwave oven, we boiled water in an MRI on several occasions. It wasn't from the magnetic field, but from the strong RF signal being a bit too strong. This only happened in our development prototypes which lacked the normal safety interlocks of production systems.

Tom


<div class='quotetop'>QUOTE(fwellers @ Oct 28 2007, 10:20 AM) [snapback]531544[/snapback]</div>

Ding ding ding...we have a winner, Bob. Tell the man what he has won...

Tom

 

<div class='quotetop'>QUOTE(Ron Howell @ Oct 28 2007, 12:33 AM) [snapback]531455[/snapback]</div>

All production vehicles are tested for EMF. Toyota and Honda have both stated in the past that the passenger compartments of their hybrids produce no more EMF than conventional vehicles. They would surely have been aware of the concerns over EMF, mostly in the US.

EMF outside of current production hybrids would probably be at the same levels, as I see no extra shielding that affects the interior alone.

 

<div class='quotetop'>QUOTE(Ron Howell @ Oct 28 2007, 03:21 PM) [snapback]531641[/snapback]</div>

The magnetic field in an MRI goes right through you, but your body doesn't absorb magnetic energy. The high magnetic field in an MR magnet is static. In fact, it is produced by a large superconducting electromagnet. Once it is powered up to the right amount of current, the power supply is disconnected and the superconducting magnet freewheels indefinitely without additional energy. Another time varying magnetic field is superimposed by a series of gradient coils which are driven by huge amplifiers, much like those used on stereo systems. The gradient coils are used to spatially encode the magnetic field. The strong magnetic field causes many of the protons in your body to align their spin with the field. While this is happening, a radio transmitter sends RF into the scanner through antennas. The RF is tuned to excite the protons, causing some of them to flip over into an anti-aligned, or higher energy state (this is the resonance phenomenon in Magnetic Resonance Imaging). When the RF is turned off, these anti-aligned protons began to flip back. Each time one flips back, it acts as a tiny radio transmitter and sends off a small RF pulse. The RF receiver system picks up these small pulses and mathematically converts them into an image.

So to answer your question, all of the energy used to create an MRI image is stored in your body, but it's only a tiny amount in the form of higher energy protons.

Tom