wrote in message
...
On Thu, 29 Nov 2007 20:12:22 GMT, Short Wave Sportfishing
wrote:

On Thu, 29 Nov 2007 13:12:52 -0500, wrote:

Another big breakthrough in electric motor efficiency is PWM, or
"pulse width modulation" used for controlling the speed

Sorry - I didn't see your answer until it was too late.

Thanks for the backup! LOL



Is it used in both AC induction motors as well as DC permanent magnet
motors?

Eisboch

wrote in message
...
On Thu, 29 Nov 2007 14:24:54 -0500, "Eisboch"
wrote:


wrote in message
. ..
On Thu, 29 Nov 2007 12:21:27 -0600, Vic Smith
wrote:

On Thu, 29 Nov 2007 13:12:52 -0500, wrote:

On Thu, 29 Nov 2007 12:05:58 -0600, Vic Smith
wrote:

On Thu, 29 Nov 2007 12:59:14 -0500, wrote:



Rare earth magnets?

Excuse my ignorance on this, but is that like Kryptonite?

--Vic

No.

Another big breakthrough in electric motor efficiency is PWM, or
"pulse width modulation" used for controlling the speed. In the old
days, you slowed down a battery powered motor by using a resistor. PWM
slows down the motor without wasting nearly as much energy. It offers
no savings at full throttle, but anything below that, it conserves
power rather than simply converting it to heat. This was a big deal
when they started using it for electric trolling motors about 20 years
ago.


That may well be what I read about. I was going to mention something
about "resistor" or "rectifier" but since I am so unversed on electric
components didn't want to muddle it up.
I do recall that the use of the innovation went beyond trolling
motors, and that it basically applied to all motors, but the article
gave emphasis on industrial use because of power cost savings.

--Vic

It's actually a pretty simple concept. Rather than reducing voltage
with a variable resistor to slow the motor, you maintain the voltage,
but pulse it on and off very rapidly. You vary the motor speed by
varying the duty cycle of the pulses between longer or shorter bursts
of power "on" or "off". The motor is pretty dumb and can't tell the
difference.



Silicon Controled Rectifier or "SCR". Two basic types ... phase angle
fired
or zero crossing. The zero crossing type generates less EMI and is
electrically "quieter".

They replaced the old variable resistance "rheostats" for light dimmers
and
induction motor speed control (such as in ceiling fans, etc.)


Not the same thing by itself. A silicon controlled rectifier regulates
the voltage up and down. In a PWM controller the output voltage (when
present) stays constant. In a 12 volt trolling motor, as an example,
the voltage being fed to the motor will be 12 volts regardless of the
speed of the motor. 12 volts at full "throttle" and 12 volts at 1/4
"throttle" The 12 volts is being switched on and off, and the output
of the motor is controlled by the relationship of the width of the ON
cycle to the OFF cycle.

Higher speed:

_________ ____________ _____________
|____| |____|

Lower Speed:
___ ____ ___
|_____________| |_____________|





To further expound on the Pulse width Modulation. The primary advantage
other than efficiency is that you get full torque at low RPM. The motors we
use are capable of huge over currents for short periods which is why the
electric drag cars use them. Think 2000Amps for Eight seconds. These
motors are series wound brush type motors. They are about as efficient as
you are going to get for reasonable money. There are also 3 phase motors
but the controllers get very expensive and you only gain about 3%
efficiency. Not worth it in my book. Other than that motors are pretty
much just plain heavy for the size needed. I have had several conservations
with sailors wanting to replace the old one lung internal combustion motors
with electric motors. To push a sailboat at hull speed takes so little
power that one of the motors we are using will push a 36' sailor. Some guys
are using even smaller motors.
The primary device used to control the high current application are power
mos fet"s (field effect transistors). They can be paralleled to get the
control power needed and they are easily controlled by low power
electronics. We are testing a new controller that we can connect the
control head to a computer to set up limits and various control functions.

Pretty cool stuff!

Tom

"Eisboch" wrote in message
...

wrote in message
...
On Thu, 29 Nov 2007 20:12:22 GMT, Short Wave Sportfishing
wrote:

On Thu, 29 Nov 2007 13:12:52 -0500, wrote:

Another big breakthrough in electric motor efficiency is PWM, or
"pulse width modulation" used for controlling the speed

Sorry - I didn't see your answer until it was too late.

Thanks for the backup! LOL



Is it used in both AC induction motors as well as DC permanent magnet
motors?

Eisboch


I checked with my friend Google and found the answer, which is "Yes".
I have to get out of my 20 year old technology and learn some new stuff.

Eisboch

On Thu, 29 Nov 2007 15:14:38 -0500, "Eisboch"
wrote:


wrote in message
.. .
On Thu, 29 Nov 2007 20:12:22 GMT, Short Wave Sportfishing
wrote:

On Thu, 29 Nov 2007 13:12:52 -0500, wrote:

Another big breakthrough in electric motor efficiency is PWM, or
"pulse width modulation" used for controlling the speed

Sorry - I didn't see your answer until it was too late.

Thanks for the backup! LOL

Is it used in both AC induction motors as well as DC permanent magnet
motors?

Well, yes - with a qualification.

My knowledge of it comes from communications technology and what I
read with respect to my new trolling motor.

But I believe it is used in both.

I could be wrong.

I often am.

Are? :)

"Short Wave Sportfishing" wrote in message
...
On Thu, 29 Nov 2007 15:14:38 -0500, "Eisboch"
wrote:


wrote in message
. ..
On Thu, 29 Nov 2007 20:12:22 GMT, Short Wave Sportfishing
wrote:

On Thu, 29 Nov 2007 13:12:52 -0500, wrote:

Another big breakthrough in electric motor efficiency is PWM, or
"pulse width modulation" used for controlling the speed

Sorry - I didn't see your answer until it was too late.

Thanks for the backup! LOL

Is it used in both AC induction motors as well as DC permanent magnet
motors?

Well, yes - with a qualification.

My knowledge of it comes from communications technology and what I
read with respect to my new trolling motor.

But I believe it is used in both.

I could be wrong.

I often am.

Are? :)


This is good stuff. (the answer is "yes"). Everyday I feel like technology
is leaving me in the dust, especially since I stopped working and trying to
keep current.

Turns out it's also responsible for the higher quality of SACD recordings.

Eisboch

On Thu, 29 Nov 2007 14:24:54 -0500, "Eisboch"
wrote:



Going back to Vic's question .... I think it was GE that introduced a super
efficient induction motor years ago for use in refrigerator compressors,
etc. I don't remember what made them more efficent though.

After some time with the devil Google, it may have been Bedini motor
circuitry I read about, but I'm still not sure.
Not nearly as credible as the Pop Mechanics article about dropping
pulverized coal on the icecaps to prevent an ice age.

--Vic

On Thu, 29 Nov 2007 15:51:52 -0500, "Eisboch"
wrote:


"Short Wave Sportfishing" wrote in message
.. .
On Thu, 29 Nov 2007 15:14:38 -0500, "Eisboch"
wrote:


wrote in message
...
On Thu, 29 Nov 2007 20:12:22 GMT, Short Wave Sportfishing
wrote:

On Thu, 29 Nov 2007 13:12:52 -0500, wrote:

Another big breakthrough in electric motor efficiency is PWM, or
"pulse width modulation" used for controlling the speed

Sorry - I didn't see your answer until it was too late.

Thanks for the backup! LOL

Is it used in both AC induction motors as well as DC permanent magnet
motors?

Well, yes - with a qualification.

My knowledge of it comes from communications technology and what I
read with respect to my new trolling motor.

But I believe it is used in both.

I could be wrong.

I often am.

Are? :)

This is good stuff. (the answer is "yes"). Everyday I feel like technology
is leaving me in the dust, especially since I stopped working and trying to
keep current.

Tell me about it. They left my mumbling to myself in '94. :)

Turns out it's also responsible for the higher quality of SACD recordings.

Didn't know that.

"Eisboch" wrote in message
...

wrote in message
...
On Thu, 29 Nov 2007 12:21:27 -0600, Vic Smith
wrote:

On Thu, 29 Nov 2007 13:12:52 -0500, wrote:

On Thu, 29 Nov 2007 12:05:58 -0600, Vic Smith
wrote:

On Thu, 29 Nov 2007 12:59:14 -0500, wrote:



Rare earth magnets?

Excuse my ignorance on this, but is that like Kryptonite?

--Vic

No.

Another big breakthrough in electric motor efficiency is PWM, or
"pulse width modulation" used for controlling the speed. In the old
days, you slowed down a battery powered motor by using a resistor. PWM
slows down the motor without wasting nearly as much energy. It offers
no savings at full throttle, but anything below that, it conserves
power rather than simply converting it to heat. This was a big deal
when they started using it for electric trolling motors about 20 years
ago.


That may well be what I read about. I was going to mention something
about "resistor" or "rectifier" but since I am so unversed on electric
components didn't want to muddle it up.
I do recall that the use of the innovation went beyond trolling
motors, and that it basically applied to all motors, but the article
gave emphasis on industrial use because of power cost savings.

--Vic

It's actually a pretty simple concept. Rather than reducing voltage
with a variable resistor to slow the motor, you maintain the voltage,
but pulse it on and off very rapidly. You vary the motor speed by
varying the duty cycle of the pulses between longer or shorter bursts
of power "on" or "off". The motor is pretty dumb and can't tell the
difference.



Silicon Controled Rectifier or "SCR". Two basic types ... phase angle
fired or zero crossing. The zero crossing type generates less EMI and is
electrically "quieter".

They replaced the old variable resistance "rheostats" for light dimmers
and induction motor speed control (such as in ceiling fans, etc.)

Going back to Vic's question .... I think it was GE that introduced a
super efficient induction motor years ago for use in refrigerator
compressors, etc. I don't remember what made them more efficent though.

Eisboch


Most of the AC was controlled by Triacs. And AC SCR. Sort of dual SCR's.
PWM is how much time the voltage is applied vs. how much off time. Should
have patented the circuit when I did my senior project in engineering at
university. Was a PWM dive light with a 555 timer controlling it and
magnetic switches for on off and intensity. In DC you will always get full
power when the power is on. On AC you can only allow power during the
higher voltage part of the sine wave and gets lots of torque. Was a design
out years ago, in the 1960's for drill speed controller that used SCR in a
Triac mode and at low speed, the drill would about rip your arm off if it
caught. Most of the modern motor controllers (Texas Insturments was the
leader in parts supply) basically keep a better phase angle, and temps down
via PWM and when the pwoer is applied.

"Eisboch" wrote in message
...

wrote in message
...
On Thu, 29 Nov 2007 20:12:22 GMT, Short Wave Sportfishing
wrote:

On Thu, 29 Nov 2007 13:12:52 -0500, wrote:

Another big breakthrough in electric motor efficiency is PWM, or
"pulse width modulation" used for controlling the speed

Sorry - I didn't see your answer until it was too late.

Thanks for the backup! LOL



Is it used in both AC induction motors as well as DC permanent magnet
motors?

Eisboch


Yup, the PWM on AC just allows a wider part of the max voltage part of a
sine wave to be passed to the motor.

On Thu, 29 Nov 2007 17:07:51 GMT, "Delburt D"
wrote:


wrote in message
...
On Nov 29, 2:24 am, "Eisboch" wrote:
"Delburt D" wrote in message

news:ILn3j.15376$B21.15016@trndny07...



Just for the record, we are using a 15000 watt battery pack that weighs
828 lbs. Add to that the battery cable, 2/0 welding cable, the charger,
this is a plug in, Controllers etc.

With battery technology what it is today we are lucky to push a nice
little light weight hull like ours as much as we can. The future
however
is looking brighter for much better batteries with higher capacity and
much less weight.

Where is the high capacity battery technology heading? The last major
advancement I am aware of was the development of lithium ion technology
but
you don't see many of those in really big battery applications. Lithium
can
also be a bit dicy in terms of handling (or getting wet) if I recall
correctly.

Seems like we are still stuck in the lead/acid age, either in wet cell or
AGM configurations despite many years of forecasts predicting major
technological breakthroughs in battery construction.

Eisboch

My little mahogany skiffs with an 8 horse will make a smaller carbon
footprint than the electric plants used to charge these things,
hopefully when I come here selling them in spring, I get such a warm
reception...

While we are looking at 15000 watt hours of power it still only takes $1.50
, ( ref $.10 / KW ) to fully charge the packs as is. Compare to $150 to
fill a 50 gal gas tank. I know we are talking a difference in performance
levels but you can still be out on the lake all day and not only make a much
smaller carbon foot print but also NO Carbon Monxide or burned oil residue
or any of the many other compounds created by burning gasoline in an
internal combustion engine.

Tom


And, most importantly, spill fewer cocktails!
--
John H