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Default Abate Holding Your Breath...Thompson's Design

On Wed, 18 Jan 2012 21:39:39 -0500, Jamie
t wrote:

Jim Thompson wrote:

On Wed, 18 Jan 2012 20:48:13 -0500, Jamie
t wrote:


Jim Thompson wrote:


On Wed, 18 Jan 2012 18:46:14 -0500, Jamie
jamie_ka1lpa_not_valid_after_ka1lpa_@charter. net wrote:

[snip]


And let us not forget that these non-pm alternators have not used
brushes for the field for years now. Nothing but bearings and the
unexpected mishap to take place now.


[snip]

Huh? How does that work?

...Jim Thompson

They have not been using brushes in alternators in cars for a long time
now. They may still use them in very large units however.

Since you never believe me on anything, maybe you can believe others.

He

http://www.pearen.ca/dunlite/BrushlessAlternators.pdf

Jamie



OK. I've not seen that in a passenger car. My Q45 has slip-rings.

...Jim Thompson


Talking about slip rings. We still operate many large AC motors (Eddy
current clutches) via slip rings.. They actually work much better for
constant tension control over today's preferred vector systems.

But, they are getting old like the rest of us and soon to see their
demise.

Jamie


As one with 50 years dealing with the car companies, they haggle over
pennies. So I suspect exciter-based alternators are still rare. I'll
ask my Infiniti mechanic if the new ones do/don't have slip rings (my
Q45 is a 2005, but only 52,000 miles on it :-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
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Default Abate Holding Your Breath...Thompson's Design

On Wed, 18 Jan 2012 15:50:39 -0500, "Tom Del Rosso"
wrote:


Jim Thompson wrote:
On Wed, 18 Jan 2012 12:01:10 -0800, John Larkin

Say why an autotransformer won't work.


Because I say so. Prove me wrong.


Surely you realize that the only way to prove it _will_ work is by building
it.


I took one of Marcel's alternator models, ran it through a 2:1
stepdown transformer, and rectified that. On the sensible parts of the
frequency curve, the resulting DC current increases, about doubling
the no-transformer current towards the high end. Impedance matching
works!

Of course with the transformer you get less output on the low end, but
then that's what the added battery is for, to power the lights at low
and zero speed.

John

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Default Abate Holding Your Breath...Thompson's Design

"John Larkin" wrote in message
...

I took one of Marcel's alternator models, ran it through a 2:1
stepdown transformer, and rectified that. On the sensible parts of the
frequency curve, the resulting DC current increases, about doubling
the no-transformer current towards the high end. Impedance
matching works!


Of course with the transformer you get less output on the low end, but
then that's what the added battery is for, to power the lights at low
and zero speed.


I just found Rick's data for the dynamo, and it appears that the RMS value
is about 1/4 the P-P voltage, instead of 1/2.8 as would be expected for a
sine wave. So I'm curious about the waveshape. And of course impedance
matching works, but I think it would be better to boost the voltage and then
rectify it so the forward drop of the diodes has less relative effect on
efficiency. Perhaps the voltage doubler would be most efficient.

Once converted to DC, impedance matching can be best attained by PWM and a
buck converter. And the step-down transformer (or any transformer) would
need to have a lot of iron to work at the lower limits where the frequency
is less than 20 Hz, although the voltage is about proportional to frequency,
so that may not be significant.

These days there are much better ways to achieve impedance matching and
maximum efficiency than by using a simple transformer. And solid state
components are much lighter and cheaper than iron core magnetics, especially
since they need to be specially wound to work optimally at the low voltages
produced by the hub generator (2-7 VRMS).

The power produced by the bike hub generator would seem to be proportional
to speed, but it may drop off at higher speed because of the higher
frequency and the inductance. This may result in a relatively constant power
output and a crude form of regulation that results in relatively little
variation in brightness over normal speed range.

Paul

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Default Abate Holding Your Breath...Thompson's Design


John Larkin wrote:

I took one of Marcel's alternator models, ran it through a 2:1
stepdown transformer, and rectified that. On the sensible parts of the
frequency curve, the resulting DC current increases, about doubling
the no-transformer current towards the high end. Impedance matching
works!


Is it for sure the impedance matching capability of the transformer that
produces the benefit, or the trade-off of current vs voltage? I ask this
because I don't see any way to be sure of any of the impedances, so how can
we know if the transformer is matching it?


--

Reply in group, but if emailing add one more
zero, and remove the last word.


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Default Abate Holding Your Breath...Thompson's Design

On Thu, 19 Jan 2012 00:04:26 -0500, "Tom Del Rosso"
wrote:


John Larkin wrote:

I took one of Marcel's alternator models, ran it through a 2:1
stepdown transformer, and rectified that. On the sensible parts of the
frequency curve, the resulting DC current increases, about doubling
the no-transformer current towards the high end. Impedance matching
works!


Is it for sure the impedance matching capability of the transformer that
produces the benefit, or the trade-off of current vs voltage? I ask this
because I don't see any way to be sure of any of the impedances, so how can
we know if the transformer is matching it?


Larkin still hasn't run the simulation. And what is this "_one_ of
Marcel's alternator models"?

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.


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Default Abate Holding Your Breath...Thompson's Design

On Wed, 18 Jan 2012 23:57:55 -0500, "P E Schoen"
wrote:

"John Larkin" wrote in message
.. .

I took one of Marcel's alternator models, ran it through a 2:1
stepdown transformer, and rectified that. On the sensible parts of the
frequency curve, the resulting DC current increases, about doubling
the no-transformer current towards the high end. Impedance
matching works!


Of course with the transformer you get less output on the low end, but
then that's what the added battery is for, to power the lights at low
and zero speed.


I just found Rick's data for the dynamo, and it appears that the RMS value
is about 1/4 the P-P voltage, instead of 1/2.8 as would be expected for a
sine wave. So I'm curious about the waveshape.


What I've seen is sort of spikey, unloaded. It will probably look a
little more sinusoidal loaded. But there are all sorts of alternators
out there.

And of course impedance
matching works, but I think it would be better to boost the voltage and then
rectify it so the forward drop of the diodes has less relative effect on
efficiency. Perhaps the voltage doubler would be most efficient.


I think there would be plenty of voltage just rectifying and
filtering. But you'd need a switcher that works over a wide voltage
range and doesn't blow up when the alternator voltage is really high,
100 volts or maybe more. That's not all that difficult, but a Digikey
transformer is a lot simpler and more reliable.



Once converted to DC, impedance matching can be best attained by PWM and a
buck converter. And the step-down transformer (or any transformer) would
need to have a lot of iron to work at the lower limits where the frequency
is less than 20 Hz, although the voltage is about proportional to frequency,
so that may not be significant.


It's only a few watts, so the transformer would be small. Use high
enough voltage windings that nothing saturates.


These days there are much better ways to achieve impedance matching and
maximum efficiency than by using a simple transformer.


Sure. But the transformer is simple and rugged.


And solid state
components are much lighter and cheaper than iron core magnetics, especially
since they need to be specially wound to work optimally at the low voltages
produced by the hub generator (2-7 VRMS).

The power produced by the bike hub generator would seem to be proportional
to speed, but it may drop off at higher speed because of the higher
frequency and the inductance. This may result in a relatively constant power
output and a crude form of regulation that results in relatively little
variation in brightness over normal speed range.


What flattens out brightness is the constant *current* (into a load,
over the speed range) of these alternators. Both voltage and frequency
increases with speed, and there's a lot of inductance.

John

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Default Abate Holding Your Breath...Thompson's Design


"John Larkin" wrote in message
...
On Wed, 18 Jan 2012 23:57:55 -0500, "P E Schoen"
wrote:

"John Larkin" wrote in message
. ..

I took one of Marcel's alternator models, ran it through a 2:1
stepdown transformer, and rectified that. On the sensible parts of the
frequency curve, the resulting DC current increases, about doubling
the no-transformer current towards the high end. Impedance
matching works!


Of course with the transformer you get less output on the low end, but
then that's what the added battery is for, to power the lights at low
and zero speed.


I just found Rick's data for the dynamo, and it appears that the RMS value
is about 1/4 the P-P voltage, instead of 1/2.8 as would be expected for a
sine wave. So I'm curious about the waveshape.


What I've seen is sort of spikey, unloaded. It will probably look a
little more sinusoidal loaded. But there are all sorts of alternators
out there.

And of course impedance
matching works, but I think it would be better to boost the voltage and
then
rectify it so the forward drop of the diodes has less relative effect on
efficiency. Perhaps the voltage doubler would be most efficient.


I think there would be plenty of voltage just rectifying and
filtering. But you'd need a switcher that works over a wide voltage
range and doesn't blow up when the alternator voltage is really high,
100 volts or maybe more. That's not all that difficult, but a Digikey
transformer is a lot simpler and more reliable.



Once converted to DC, impedance matching can be best attained by PWM and a
buck converter. And the step-down transformer (or any transformer) would
need to have a lot of iron to work at the lower limits where the frequency
is less than 20 Hz, although the voltage is about proportional to
frequency,
so that may not be significant.


It's only a few watts, so the transformer would be small. Use high
enough voltage windings that nothing saturates.


These days there are much better ways to achieve impedance matching and
maximum efficiency than by using a simple transformer.


Sure. But the transformer is simple and rugged.


And solid state
components are much lighter and cheaper than iron core magnetics,
especially
since they need to be specially wound to work optimally at the low
voltages
produced by the hub generator (2-7 VRMS).

The power produced by the bike hub generator would seem to be proportional
to speed, but it may drop off at higher speed because of the higher
frequency and the inductance. This may result in a relatively constant
power
output and a crude form of regulation that results in relatively little
variation in brightness over normal speed range.


What flattens out brightness is the constant *current* (into a load,
over the speed range) of these alternators. Both voltage and frequency
increases with speed, and there's a lot of inductance.

John


Were there spice/LTspice models somewhere or were you referring to the
graphs & tables?


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Default Abate Holding Your Breath...Thompson's Design


"Jim Thompson" wrote in
message ...
On Thu, 19 Jan 2012 00:04:26 -0500, "Tom Del Rosso"
wrote:


John Larkin wrote:

I took one of Marcel's alternator models, ran it through a 2:1
stepdown transformer, and rectified that. On the sensible parts of the
frequency curve, the resulting DC current increases, about doubling
the no-transformer current towards the high end. Impedance matching
works!


Is it for sure the impedance matching capability of the transformer that
produces the benefit, or the trade-off of current vs voltage? I ask this
because I don't see any way to be sure of any of the impedances, so how
can
we know if the transformer is matching it?


Larkin still hasn't run the simulation. And what is this "_one_ of
Marcel's alternator models"?


That's what I'd like to know.


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Default Abate Holding Your Breath...Thompson's Design

On Thu, 19 Jan 2012 07:57:52 -0700, Jim Thompson
wrote:

On Thu, 19 Jan 2012 00:04:26 -0500, "Tom Del Rosso"
wrote:


John Larkin wrote:

I took one of Marcel's alternator models, ran it through a 2:1
stepdown transformer, and rectified that. On the sensible parts of the
frequency curve, the resulting DC current increases, about doubling
the no-transformer current towards the high end. Impedance matching
works!


Is it for sure the impedance matching capability of the transformer that
produces the benefit, or the trade-off of current vs voltage? I ask this
because I don't see any way to be sure of any of the impedances, so how can
we know if the transformer is matching it?


Larkin still hasn't run the simulation. And what is this "_one_ of
Marcel's alternator models"?

...Jim Thompson



I have run it, assuming 6 ohms and 50 mH in the source. I proved that
transformers can match impedances.

It wasn't worth doing, since everybody already knows that transformers
can match inpedances. I was actually trying something else to boost
the current (namely adding an inductor after the rectifier) which only
helped 10 or 20%, not enough to publish. Some of the waveforms were
amazing. Once I had that model, it was easy to stick in a transformer,
so I did. It worked the way transformers are supposed to work.

John

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Default Abate Holding Your Breath...Thompson's Design


"P E Schoen" wrote in message
...
"Jamie" wrote in message ...

And let us not forget that these non-pm alternators have not used brushes
for the field for years now. Nothing but bearings and the unexpected
mishap to take place now.


According to one reference, some models of wheel hub generators had problems
with water entering the enclosure when the bike was moved from a warm garage
to the cold outdoors and ridden in the rain. The temperature differential
created a relative vacuum in the hub which sucked water in through the seals
which were not designed with that in mind. Newer models apparently corrected
the problem. But if water does enter the assembly it tends to corrode the
rotor and stator poles which have very small clearance and cause them to
bind.

Paul

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv

The old SA 'dynamos' have no seals of any kind but water can easily run out,
with the combined generator/gear hub there's a tendency for the generator
internals to get well oiled via the bearing.

I've never seen one corrode.




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Default Abate Holding Your Breath...Thompson's Design


"Jim Thompson" wrote in
message ...
On Wed, 18 Jan 2012 18:46:14 -0500, Jamie
t wrote:

[snip]

And let us not forget that these non-pm alternators have not used
brushes for the field for years now. Nothing but bearings and the
unexpected mishap to take place now.

[snip]

Huh? How does that work?


The type used on motorcycles has a "claw" type poles arrangement, but
instead of them being fixed to a core in the middle with the field winding
on - the claw fingers are brazed together with non-magnetic spacers.

The field winding is static and magnetically coupled to the claw poles
coaxially. The inner claw is integral with the taper that fits on the end of
the crankshaft and also extends to form the center pole.

The outer claw poles are simply a brazed on ring of poles that form the
outer of the coaxial poles.


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Default Abate Holding Your Breath...Thompson's Design

On Thu, 19 Jan 2012 07:35:32 -0800, John Larkin
wrote:

On Thu, 19 Jan 2012 07:57:52 -0700, Jim Thompson
wrote:

On Thu, 19 Jan 2012 00:04:26 -0500, "Tom Del Rosso"
wrote:


John Larkin wrote:

I took one of Marcel's alternator models, ran it through a 2:1
stepdown transformer, and rectified that. On the sensible parts of the
frequency curve, the resulting DC current increases, about doubling
the no-transformer current towards the high end. Impedance matching
works!

Is it for sure the impedance matching capability of the transformer that
produces the benefit, or the trade-off of current vs voltage? I ask this
because I don't see any way to be sure of any of the impedances, so how can
we know if the transformer is matching it?


Larkin still hasn't run the simulation. And what is this "_one_ of
Marcel's alternator models"?

...Jim Thompson



I have run it, assuming 6 ohms and 50 mH in the source.


That's NOT the Magdowski model. I suggest you re-read the Magdowski
paper... it has some shunt losses.

I proved that
transformers can match impedances.


I didn't know that [snicker]


It wasn't worth doing, since everybody already knows that transformers
can match inpedances. I was actually trying something else to boost
the current (namely adding an inductor after the rectifier) which only
helped 10 or 20%, not enough to publish. Some of the waveforms were
amazing. Once I had that model, it was easy to stick in a transformer,
so I did. It worked the way transformers are supposed to work.

John


Maybe Ian should build your solution and report back ?:-}

I'm thinking of buying a recent vintage hub just for yucks and
characterizing it myself. Quoting a line from "The Sting", "I already
know how to get drunk" :-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
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Default Abate Holding Your Breath...Thompson's Design

On Thu, 19 Jan 2012 15:34:24 -0000, "Ian Field"
wrote:


"John Larkin" wrote in message
.. .
On Wed, 18 Jan 2012 23:57:55 -0500, "P E Schoen"
wrote:

"John Larkin" wrote in message
...

I took one of Marcel's alternator models, ran it through a 2:1
stepdown transformer, and rectified that. On the sensible parts of the
frequency curve, the resulting DC current increases, about doubling
the no-transformer current towards the high end. Impedance
matching works!

Of course with the transformer you get less output on the low end, but
then that's what the added battery is for, to power the lights at low
and zero speed.

I just found Rick's data for the dynamo, and it appears that the RMS value
is about 1/4 the P-P voltage, instead of 1/2.8 as would be expected for a
sine wave. So I'm curious about the waveshape.


What I've seen is sort of spikey, unloaded. It will probably look a
little more sinusoidal loaded. But there are all sorts of alternators
out there.

And of course impedance
matching works, but I think it would be better to boost the voltage and
then
rectify it so the forward drop of the diodes has less relative effect on
efficiency. Perhaps the voltage doubler would be most efficient.


I think there would be plenty of voltage just rectifying and
filtering. But you'd need a switcher that works over a wide voltage
range and doesn't blow up when the alternator voltage is really high,
100 volts or maybe more. That's not all that difficult, but a Digikey
transformer is a lot simpler and more reliable.



Once converted to DC, impedance matching can be best attained by PWM and a
buck converter. And the step-down transformer (or any transformer) would
need to have a lot of iron to work at the lower limits where the frequency
is less than 20 Hz, although the voltage is about proportional to
frequency,
so that may not be significant.


It's only a few watts, so the transformer would be small. Use high
enough voltage windings that nothing saturates.


These days there are much better ways to achieve impedance matching and
maximum efficiency than by using a simple transformer.


Sure. But the transformer is simple and rugged.


And solid state
components are much lighter and cheaper than iron core magnetics,
especially
since they need to be specially wound to work optimally at the low
voltages
produced by the hub generator (2-7 VRMS).

The power produced by the bike hub generator would seem to be proportional
to speed, but it may drop off at higher speed because of the higher
frequency and the inductance. This may result in a relatively constant
power
output and a crude form of regulation that results in relatively little
variation in brightness over normal speed range.


What flattens out brightness is the constant *current* (into a load,
over the speed range) of these alternators. Both voltage and frequency
increases with speed, and there's a lot of inductance.

John


Were there spice/LTspice models somewhere or were you referring to the
graphs & tables?


Marcel's graphs, and others I've seen, are consistent with the simple
model of a voltage source (voltage tracking frequency) in series with
a resistance and an inductance. After all, that's what's actually
inside the hub.

If the pole pieces have funny shapes, the waveforms can be
non-sinusoidal. In as much as the designs usually attempt to deliver
constant current into a load, waveform distortion is equivalent to
higher frequency, which only helps.

Loading will make the current waveform more sinusoidal than the
open-circuit voltage waveform.

If one desires to rectify and filter, and then switch down, the
lightly-loaded capacitor voltage could be very high if the distorted
waveform has a high crest factor... you could get higher DC than the
RMS voltage suggests.

John

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Default Abate Holding Your Breath...Thompson's Design

On Thu, 19 Jan 2012 15:49:47 -0000, "Ian Field"
wrote:


"Jim Thompson" wrote in
message ...
On Wed, 18 Jan 2012 18:46:14 -0500, Jamie
t wrote:

[snip]

And let us not forget that these non-pm alternators have not used
brushes for the field for years now. Nothing but bearings and the
unexpected mishap to take place now.

[snip]

Huh? How does that work?


The type used on motorcycles has a "claw" type poles arrangement, but
instead of them being fixed to a core in the middle with the field winding
on - the claw fingers are brazed together with non-magnetic spacers.

The field winding is static and magnetically coupled to the claw poles
coaxially. The inner claw is integral with the taper that fits on the end of
the crankshaft and also extends to form the center pole.

The outer claw poles are simply a brazed on ring of poles that form the
outer of the coaxial poles.


Hey, I suggested that, but didn't think it would work! I figured there
would be too much reluctance in the field path, but that geometry
seems to fix that.

John

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Default Abate Holding Your Breath...Thompson's Design

On Thu, 19 Jan 2012 08:43:48 -0800, John Larkin
wrote:

On Thu, 19 Jan 2012 15:34:24 -0000, "Ian Field"
wrote:


"John Larkin" wrote in message
. ..
On Wed, 18 Jan 2012 23:57:55 -0500, "P E Schoen"
wrote:

"John Larkin" wrote in message
m...

I took one of Marcel's alternator models, ran it through a 2:1
stepdown transformer, and rectified that. On the sensible parts of the
frequency curve, the resulting DC current increases, about doubling
the no-transformer current towards the high end. Impedance
matching works!

Of course with the transformer you get less output on the low end, but
then that's what the added battery is for, to power the lights at low
and zero speed.

I just found Rick's data for the dynamo, and it appears that the RMS value
is about 1/4 the P-P voltage, instead of 1/2.8 as would be expected for a
sine wave. So I'm curious about the waveshape.

What I've seen is sort of spikey, unloaded. It will probably look a
little more sinusoidal loaded. But there are all sorts of alternators
out there.

And of course impedance
matching works, but I think it would be better to boost the voltage and
then
rectify it so the forward drop of the diodes has less relative effect on
efficiency. Perhaps the voltage doubler would be most efficient.

I think there would be plenty of voltage just rectifying and
filtering. But you'd need a switcher that works over a wide voltage
range and doesn't blow up when the alternator voltage is really high,
100 volts or maybe more. That's not all that difficult, but a Digikey
transformer is a lot simpler and more reliable.



Once converted to DC, impedance matching can be best attained by PWM and a
buck converter. And the step-down transformer (or any transformer) would
need to have a lot of iron to work at the lower limits where the frequency
is less than 20 Hz, although the voltage is about proportional to
frequency,
so that may not be significant.

It's only a few watts, so the transformer would be small. Use high
enough voltage windings that nothing saturates.


These days there are much better ways to achieve impedance matching and
maximum efficiency than by using a simple transformer.

Sure. But the transformer is simple and rugged.


And solid state
components are much lighter and cheaper than iron core magnetics,
especially
since they need to be specially wound to work optimally at the low
voltages
produced by the hub generator (2-7 VRMS).

The power produced by the bike hub generator would seem to be proportional
to speed, but it may drop off at higher speed because of the higher
frequency and the inductance. This may result in a relatively constant
power
output and a crude form of regulation that results in relatively little
variation in brightness over normal speed range.

What flattens out brightness is the constant *current* (into a load,
over the speed range) of these alternators. Both voltage and frequency
increases with speed, and there's a lot of inductance.

John


Were there spice/LTspice models somewhere or were you referring to the
graphs & tables?


Marcel's graphs, and others I've seen, are consistent with the simple
model of a voltage source (voltage tracking frequency) in series with
a resistance and an inductance. After all, that's what's actually
inside the hub.

If the pole pieces have funny shapes, the waveforms can be
non-sinusoidal. In as much as the designs usually attempt to deliver
constant current into a load, waveform distortion is equivalent to
higher frequency, which only helps.

Loading will make the current waveform more sinusoidal than the
open-circuit voltage waveform.

If one desires to rectify and filter, and then switch down, the
lightly-loaded capacitor voltage could be very high if the distorted
waveform has a high crest factor... you could get higher DC than the
RMS voltage suggests.

John


Build it, Ian, Larkin says it'll work O:-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
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