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Re: Air Coupled EV Charging
On Saturday, March 23, 2019 at 2:23:30 PM UTC-4, John Larkin wrote:
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Looks like Momentum Dynamics stumped the chump on this one.  

Rick C.  

Re: Air Coupled EV Charging
It will never be better efficiently than a connector. Differences in efficiencies are due to different converter topology and components  

Inductive is near field

Resonant is matched tanks on both sides, with both frequency and impedance matching  

Think of an audio tuning fork. Since it is resonant the distance is not that important since in resonant operation the leakage inductance has reactive power

Cheers

Klaus  

Re: Air Coupled EV Charging
On Saturday, March 23, 2019 at 2:42:52 PM UTC-4, Klaus Kragelund wrote:
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What do you base that on?  What do you actually know about EV charging and the losses involved?  Do you know anything about the cable sizes they use for the current chargers?  How much power is lost in the cable and connector?  


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I think any discussion of the Momentum Dynamics device would require actually learning about how it works.  Anything else is just speculation.  

Rick C.  

Re: Air Coupled EV Charging
On Saturday, March 23, 2019 at 1:50:13 PM UTC-5, snipped-for-privacy@gmail.com wro
te:
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ficiencies are due to different converter topology and components  
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d the losses involved?  Do you know anything about the cable sizes they use
 for the current chargers?  How much power is lost in the cable and connect
or?  
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You may be well right that he doesn't know. That can be found by a table, w
ire size and current, not hard. However anyone claiming that magnetism is a
 more efficient way to transfer power than a piece of wire has some convinc
ing to do before I buy it.  

I do however admit that inductive, if efficient enough is the way to go. Co
nnectors are a pain in the ass and they are also out in the elements. they  
will corrode and eventually let out some smoke and then how much to replace
 ? That 75 watt Hakko is not likely to be able to handle the job.  

If there is empirical evidence that inductive or resonant can be more effic
ient than wire there has to be a reason. Something deficient in the connect
ors or something, though that would be heat and that would be smoke and tha
t would Al Fine.  

I just don't see it, enlighten me. How the hell can it be better than a pie
ce of wire ?

Re: Air Coupled EV Charging
On Wednesday, March 27, 2019 at 4:18:05 PM UTC-4, snipped-for-privacy@gmail.com wrote:
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rote:
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efficiencies are due to different converter topology and components  
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and the losses involved?  Do you know anything about the cable sizes they u
se for the current chargers?  How much power is lost in the cable and conne
ctor?  
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 wire size and current, not hard. However anyone claiming that magnetism is
 a more efficient way to transfer power than a piece of wire has some convi
ncing to do before I buy it.  

No one is asking you to buy it.  This is between the taxi owners and the po
wer providers.  One of them will need to pay for the losses.  I don't think
 the company making the equipment will get away with lying about the effici
ency since this will be money from someone's wallet.  


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Connectors are a pain in the ass and they are also out in the elements. the
y will corrode and eventually let out some smoke and then how much to repla
ce ? That 75 watt Hakko is not likely to be able to handle the job.  

Not just a PITA, but in the use case of the taxi being charged while in the
 moving line of a taxi queue connectors are a no-go.  


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icient than wire there has to be a reason. Something deficient in the conne
ctors or something, though that would be heat and that would be smoke and t
hat would Al Fine.  

I believe someone pointed out that the rest of the power supply system is d
ifferent as well.  Providing DC power to an EV is not without losses before
 it reaches the cable and connector, although I don't think you appreciate  
the current flowing.  I recall the number 400 volts being used in charging  
discussions and I this system provides 74 kW.  That's almost 200 amps!  The
 cable that connects to the car has to be flexible with lots of strands.  I
 don't know what gauge they use, I do know the cables I've used get hot.  I
 believe it would take a fair amount of wasted power for it to heat up that
 much.  It's a damn thick cable, about the size of a gas pump hose, but muc
h heavier and stiffer.  Then there are some 10's or 100's of feet to the ca
binet where the converters are housed.  


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iece of wire ?

You don't actually know anything about the system do you?  Stop focusing on
 a piece of wire and look at the system.  

--  

  Rick C.

  ++ Get a 1,000 miles of free Supercharging
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Re: Air Coupled EV Charging
On Wed, 27 Mar 2019 15:05:11 -0700 (PDT),
snipped-for-privacy@gmail.com wrote:

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Which partner is responsible to limit the charging current ? Is it the
charging station or the electronics in the car ? The charging should
start at full current and then it should start to drop.

Making an unregulated 400 Vdc power supply capable of a few hundred
anps is not a big deal with 6, 12 or 18 pulse rectifier thus with 2 to
6 diode voltage drops, the efficiency would be very high. Adding
accurate voltage.and current regulation complicates things.

If the current regulation us not done in the external charger, then it
must be done within the car,.

Most likely the low direct coupling efficiency might include MV/LV
transformer losses, rectification losses in charging station as well
as current limit in charging station and/or in car electronics.  

The high RF efficiency suggests that it only contains the losses in
the pick-up coil and RF rectification, thus comparing apples with
oranges.
  


Re: Air Coupled EV Charging
On Wednesday, March 27, 2019 at 7:03:01 PM UTC-4, snipped-for-privacy@downunder.com wr
ote:
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s different as well.  Providing DC power to an EV is not without losses bef
ore it reaches the cable and connector, although I don't think you apprecia
te the current flowing.  I recall the number 400 volts being used in chargi
ng discussions and I this system provides 74 kW.  That's almost 200 amps!  
The cable that connects to the car has to be flexible with lots of strands.
  I don't know what gauge they use, I do know the cables I've used get hot.
  I believe it would take a fair amount of wasted power for it to heat up t
hat much.  It's a damn thick cable, about the size of a gas pump hose, but  
much heavier and stiffer.  Then there are some 10's or 100's of feet to the
 cabinet where the converters are housed.  
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The car is always the boss, or in reality, the battery management system (B
MS).  The charger (or EVSE, a not so friendly term) simply reports to the c
ar the available current.  The car then uses what it needs up to that level
.  


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I'm sure that is not the case as it won't fool any of the operators.  They  
will be measuring the power drawn from the utility and the power supplied t
o the car.  If this company is spouting BS it will be discovered very quick
ly.  Only Donald Trump lies even when everyone knows he is lying.  

--  

  Rick C.

  --+ Get a 1,000 miles of free Supercharging
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Re: Air Coupled EV Charging
On Sat, 23 Mar 2019 11:42:48 -0700 (PDT), Klaus Kragelund

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I understand resonance. I don't understand how it can be efficient
charging a car at any distance. The field will be all over the place.
Better hope there's no rerod in the floor or damp dirt underneath.

People keep discovering the miracle of resonant charging. I think even
MIT got some press on that.




--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: Air Coupled EV Charging
On Saturday, March 23, 2019 at 2:36:42 PM UTC-7, John Larkin wrote:

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It is a matter of flux coupling, and resonance improves the effective
coupling constant.     If you need to voltage-convert
and current-limit and rectify, why not  magnetic coupling?  

In a conventional, no-tuning transformer, with low coupling, energy
stops at the primary; in resonant windings, it has Q  chances to get into the
secondary before it is lost.

Re: Air Coupled EV Charging
wrote:

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Why? The mutual inductance between two coils doesn't change if you
connect a cap across either one.


--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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Re: Air Coupled EV Charging
On 3/25/19 2:01 PM, John Larkin wrote:
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Current goes up, though.  The optimal Q probably isn't very high.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Air Coupled EV Charging
On Mon, 25 Mar 2019 14:34:53 -0400, Phil Hobbs

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On the transmit end, if a black box drives the coil, there's no way to
know if there is a resonating cap inside the box, as long as the coil
voltage is what you want.

I think a similar argument can be applied at the receiver. Resonating
is just impedance matching, not magic. But spraying h-field all around
the garage seems inefficient to me.

I have done resonant power transfer (to read out an electric meter if
mains power is off, as it is often in India) but I didn't care about
efficiency.


--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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Re: Air Coupled EV Charging
On 3/25/19 2:54 PM, John Larkin wrote:
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Right, but if it's near resonance, there's a circulating current inside  
the tank that makes the magnetic coupling stronger.  IIRC it goes like  
sqrt(Q) or something like that.  Loading it down to get power transfer  
destroys the Q, so I expect that the optimum will be somewhere like Q ~  
1 or 2.

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Doesn't matter unless something absorbs it significantly, or you have a  
pacemaker. ;)

Cheers

Phil Hobbs


--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Air Coupled EV Charging
On Mon, 25 Mar 2019 18:32:21 -0400, Phil Hobbs

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Rerod, dirt, house wiring, car body, 6-packs of whatever, washing
machine, bedsprings in the room above. It's like Tesla's scheme to
broadcast power everywhere.

Hey, a neighbor could put a tank coil in *his* garage and steal your
power. Or sue you if his dog gets cancer.




--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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Re: Air Coupled EV Charging
On Monday, March 25, 2019 at 6:51:34 PM UTC-4, John Larkin wrote:
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This isn't a Tesla idea.  Why do you hate Tesla so much that you project all EV matters onto Tesla?  

--  

  Rick C.

  - Get a 1,000 miles of free Supercharging
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Re: Air Coupled EV Charging
"
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This isn't a Tesla idea.  Why do you hate Tesla so much that you project all EV matters onto Tesla? "

I think he is talking about Tesla the (old) man, not Tesla the car company.


Re: Air Coupled EV Charging
On Monday, 25 March 2019 15:51:34 UTC-7, John Larkin  wrote:
..
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...

Err, no.

The ferrite cores used ensure that the field drops off within a few centimeters. There are health safety limits that ensure that the field that can be accessible to a human (or other animal etc) is is very low.

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The field would be negligible at a neighbor's house and it would only be active when the car is actually charging.

The receive to transmit coil distance is measured in single digit cm - if there is no car there to communicate with the transmitter or any leakage etc is detected the energization is disabled.

kw

Re: Air Coupled EV Charging
On Tuesday, 26 March 2019 00:29:29 UTC+1, snipped-for-privacy@kjwdesigns.com  wrote:
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A couple of years ago there was a paper at APEC (APEC-conf.org) investigating the effects on humans and animals. Conclusion: no real danger

Cheers

Klaus

Re: Air Coupled EV Charging
On Mon, 25 Mar 2019 16:29:25 -0700 (PDT), snipped-for-privacy@kjwdesigns.com wrote:

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The recurring pattern is that someone rediscovers resonance, takes out
10 or 20 patents, makes fuzzy claims, raises 10 or 20 million dollars,
and disappears. It happened for cell phone charging and now for cars.
The usual claim is that the resonant coupling works at great
distances. Investors seem to like it; maybe they are thinking of
tuning forks and violins.

It's just impedance matching. If it makes near-field loop coupling
easier, fine. But it's not going to be anywhere as efficient as a
simple connector.


--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: Air Coupled EV Charging
On Monday, 25 March 2019 23:51:34 UTC+1, John Larkin  wrote:
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No, it's not. It is actually directed somewhat since ferrite is place on the back of each coil

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Nope

When you are further than 10 times the diameter of the coil the field is low

Cheers

Klaus

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