On Tue, 28 Dec 2004 16:19:02 -0800, Frank Gilliland
wrote in
:

snip
.....But if the
supply voltage can be increased while maintaining the same collector
current (by changing the BE bias).....


Correction: that should be "by maintaining the same BE bias".

I mistakenly assumed that the base bias would need to be adjusted
after an increase in power supply voltage, disregarding the fact that
some amps have regulated bias supplies.

Hello Frank:

This maybe a little long winded but I learned something neat here.

That's a good call having separate amp meters off each alternator.
I am sure one alternator will want to source most of the current, but
thats ok, as the second alternator will have to kick in when the load is
applied. When the load goes nutz-oid wanting a Bazillion amps I am sure
the output current will be close to equal, if the voltage regulators are
set close to each other.

While working as a marine technican/electrican for several years, in Los
Angles I was called to a boat having alternator problems. I talked with
the boat owner and came prepared with a new marine grade alternator and
regulator.

The boat had two engines and each engine had 2 alternators. As the
electrical system needed a redundant back up everything as it did
research and commercial work out at sea for long periods of time. Time
is money and money is time stuff here.

The owner said that when the Engine #1 auxiliary alternator was placed
on line the running voltage did not increase as with the normal main
alternator did. Same for #2 Engine.

Well as the engines where running the main alternator was carrying the
load and you could not see the auxiliary alternator come on line by just
looking at the systems 24 volt system voltage. After pulling off the
field wire from the main alternator, we verified the auxiliary
alternator was really working putting out the needed current to run the
boats 24 volt electrical system. The auxiliary alternators where placed
on line by a lever that over centered and locked into place tightening
the belt that turned the alternator pulley, pretty neat!

Ok so everything was working as we verified the alternators, batteries,
and had to replace a few battery connections. No big deal.

The owner asked me to check out the electrical system #1 and #2 cross
over operation.

The boat or really a ship had to have two of everything, Two: HF Radios,
VHF Radios, Lightening Systems, Engine Indicating Meters and Indicator
Clusters, CB Radios, and of course all of the Nav Electronics like
Radars, ADF, Loran, Depth Finder, Automatic Pilot, and bunches of other
stuff. Ok so every thing ran off the 24 volt system #1 or #2.

But they didn't know how the electrical system #1 and #2 crossed over or
ran the other system when one of the engines was shut down, and wanted
to know how to operate and test it out. I didn't know either as I
couldn't find a cross over contactor relay any where.

After looking over the ships wiring diagram, I saw the cross over
contactor or relay, it had to be turned on (by a switch in the wheel
house) to allow the two electrical systems to be tied together for high
current operation.

But the neat thing that I found was that the two electrical system where
tied together thru a calculated resistance, in this case a short length
of 8 gauge steel wire that would only allow so much current to flow
between the two electrical systems. This allowed the system #1 to be up
and running and be able to run a few things on system #2, and charge the
system #2 batteries, and visa versa. This also allowed the main system
running to not be pulled down by a short in the other system.

The electrical control panel in the wheel house showed all the
alternator voltages and currents. You where able to select which of the
3 battery sets to start the engines, pretty neat. They had a small 4
cyclender gas engine that ran again two alternators and a hydraulic pump
for a auxiliary back up. And a gas powered Honda Generator mounted just
aft of the wheel house to supply 12, 24VDC, and 115 VAC for a back up
back up. Neat stuff.

So a calculated resistance coupled connection between two alternators
would allow the alternators to run separated systems and allow say a
second alternator to back up the other system while not loading it
down. Food for thought.

Jay in the Mojave


Frank Gilliland wrote:

On Tue, 28 Dec 2004 04:11:38 -0800, Jay in the Mojave
wrote in :

snip

Is this advice from experience?



Actually, yes.

Ok I have not heard of this noise but will keep an ear for it.



Even better, install two ammeters (one on each alternator) and watch
how they -don't- share the load equally.


snip

Maybe that's why Motorola designated their cheap CB amp transistors as
MRF454 and MRF455 -- to appeal to the 'big engine' mentality.

Yeah I am sure thats possible, but the nerd linger who designates the
numbers I am sure sets behind a desk and has his car serviced by normal
people.



What's 'normal'?



I would have a number like MRF-HP/454CI-Inc. hehehehehhehe

Matched transistors would go by Balanced MRF-HP/454CI-Hipo Inc
Or even PT2M454-Hipo Inc (Pettle to the Metal) OH YEAH!



So if the amp has a cooling then it's got a 'blower'? Doesn't matter
since it probably wouldn't pass the emissions inspection. And the
bubble really bursts when you realize that it takes 3kW to equal the
power of a lawnmower engine. So throttle up that moped, Jay -- you be
ridin' with the big boys!

On Wed, 29 Dec 2004 13:37:17 GMT, Lancer wrote in
htb5t058gbfee852kcbtht6vcul2jud5lu@2355323778:

snip
Ok Lancer (whichever one you are);


The same Lancer that has been here all along..


In your headers I saw several different servers, two different
newsreaders and two domain addresses (rock.com & ock.com). With all
the forgeries in this group it's easy to see how one might think your
posts are being made by more than one person.


Please explain, (CE bias can be as high as 3-4 volts under heavy load.

Isn't that set by the operating point set by bias you put on the base?


A bipolar transistor requires both a BE bias -and- a CE bias.


Ok, thats he part that I'm not understanding. (We are talking common
emitter, right?) Transistors don't require a CE bias. In the case of
an NPN just Pos voltage on the collector and Neg on the emitter. The
CE voltage is set by the bias on the BE junction.


Remember that a bipolar transistor is a -current- amplifier, not a
voltage amplifier. Saturation is a characteristic of the collector's
-current-; the CE bias is a characteristic of it's voltage. The two
terms are often used synonymously and saturation curves are really CE
bias curves, but that's because 'saturation' has two definitions:

First, it is the point where a device will no longer respond to an
increase at the input. This can happen for many reasons. But in this
case it's because the output has hit the rail, and the rail is the CE
bias (explained later).

Second, it's the point where a transistor is driven so hard that it
causes a forward bias of the BC junction (bad news).

Now..... I'm not trying to dumb this down, but simplification might
help to consolidate our differences:

Consider a transistor configured as a DC constant-current source; i.e,
base bias is fixed and therefore the collector current is constant.
Let's say the collector current is fixed at 1 amp. That current is
constant regardless of the collector voltage..... to a point: Let's
also assume that the CE bias is 2 volts when collector current is 1
amp. If the collector voltage drops below 2 volts then the collector
current will drop. Therefore, the voltage required to put the
transistor into the constant-current part of the curve is the CE bias.

Now let's configure the amplifier for Class B, use a 12 volt supply
and feed it some AC. If the peak output current is 1 amp then the
maximum possible voltage output of the amp will be 12 volts minus the
CE bias of 2 volts, or 10 volts. If the CE bias increases to 4 volts
at 10 amps (realistic value) then the peak voltage can be no larger
than 8 volts, or 2/3 of the power supply voltage.

Ok, now let's double the power supply voltage. Since the collector
current doesn't change then the CE bias doesn't change. The output can
now swing 20 volts, or 24 volts minus the CE bias. And this is 83.3%
of the ps voltage. Since the current is the same regardless of ps
voltage, the efficiency is 25% better with the -higher- ps voltage.


snip
Or are you refering to the losses in the transistor when its fully
turned on?


Not necessarily. CE bias increases with collector current regardless
of saturation (and RF bipolars don't saturate easily). But if the
supply voltage can be increased while maintaining the same collector
current (by changing the BE bias), the loss due to CE bias is not
changed, and that loss is therefore made to be a smaller percentage of
the output power. IOW, the transistor is more efficient with a higher
supply voltage.




If you don't change the CE current, the actual loss in the transistor
hasn't changed. If you increase the supply voltage it will be a
smaller percentage than it was before.


Exactly. A smaller percentage of the input power, and therefore more
efficient.

On Wed, 29 Dec 2004 06:50:36 -0800, Jay in the Mojave
wrote in :

snip
So a calculated resistance coupled connection between two alternators
would allow the alternators to run separated systems and allow say a
second alternator to back up the other system while not loading it
down. Food for thought.


Current equalizing resistors is another way to do it. It's common
practice in SS audio amps to use emitter resistors to equalize the
currents between parallel transistors. But I would hesitate using them
with modern alternators because I don't know how it would screw with
the regulators -- some have a local sense line and others have a
remote sense line -- a resistor in the load might send the regulator
into seizures.

On Wed, 29 Dec 2004 07:01:45 -0800, Frank Gilliland
wrote:

On Wed, 29 Dec 2004 13:37:17 GMT, Lancer wrote in
htb5t058gbfee852kcbtht6vcul2jud5lu@2355323778 :

snip
Ok Lancer (whichever one you are);


The same Lancer that has been here all along..


In your headers I saw several different servers, two different
newsreaders and two domain addresses (rock.com & ock.com). With all
the forgeries in this group it's easy to see how one might think your
posts are being made by more than one person.


Don't know where the ock.com came from, maybe I screwed up when I set
a news client up. I do understand what your saying tho.


Please explain, (CE bias can be as high as 3-4 volts under heavy load.

Isn't that set by the operating point set by bias you put on the base?


A bipolar transistor requires both a BE bias -and- a CE bias.


Ok, thats he part that I'm not understanding. (We are talking common
emitter, right?) Transistors don't require a CE bias. In the case of
an NPN just Pos voltage on the collector and Neg on the emitter. The
CE voltage is set by the bias on the BE junction.


Remember that a bipolar transistor is a -current- amplifier, not a
voltage amplifier. Saturation is a characteristic of the collector's
-current-; the CE bias is a characteristic of it's voltage. The two
terms are often used synonymously and saturation curves are really CE
bias curves, but that's because 'saturation' has two definitions:

First, it is the point where a device will no longer respond to an
increase at the input. This can happen for many reasons. But in this
case it's because the output has hit the rail, and the rail is the CE
bias (explained later).

Second, it's the point where a transistor is driven so hard that it
causes a forward bias of the BC junction (bad news).

Now..... I'm not trying to dumb this down, but simplification might
help to consolidate our differences:

Consider a transistor configured as a DC constant-current source; i.e,
base bias is fixed and therefore the collector current is constant.
Let's say the collector current is fixed at 1 amp. That current is
constant regardless of the collector voltage..... to a point: Let's
also assume that the CE bias is 2 volts when collector current is 1
amp. If the collector voltage drops below 2 volts then the collector
current will drop. Therefore, the voltage required to put the
transistor into the constant-current part of the curve is the CE bias.

Now let's configure the amplifier for Class B, use a 12 volt supply
and feed it some AC. If the peak output current is 1 amp then the
maximum possible voltage output of the amp will be 12 volts minus the
CE bias of 2 volts, or 10 volts. If the CE bias increases to 4 volts
at 10 amps (realistic value) then the peak voltage can be no larger
than 8 volts, or 2/3 of the power supply voltage.

Ok, now let's double the power supply voltage. Since the collector
current doesn't change then the CE bias doesn't change. The output can
now swing 20 volts, or 24 volts minus the CE bias. And this is 83.3%
of the ps voltage. Since the current is the same regardless of ps
voltage, the efficiency is 25% better with the -higher- ps voltage.


snip
Or are you refering to the losses in the transistor when its fully
turned on?


Not necessarily. CE bias increases with collector current regardless
of saturation (and RF bipolars don't saturate easily). But if the
supply voltage can be increased while maintaining the same collector
current (by changing the BE bias), the loss due to CE bias is not
changed, and that loss is therefore made to be a smaller percentage of
the output power. IOW, the transistor is more efficient with a higher
supply voltage.




If you don't change the CE current, the actual loss in the transistor
hasn't changed. If you increase the supply voltage it will be a
smaller percentage than it was before.


Exactly. A smaller percentage of the input power, and therefore more
efficient.


Thanks Frank.

Frank Gilliland wrote:
On Wed, 29 Dec 2004 13:37:17 GMT, Lancer wrote in
htb5t058gbfee852kcbtht6vcul2jud5lu@2355323778:

snip
Ok Lancer (whichever one you are);


The same Lancer that has been here all along..

In your headers I saw several different servers, two different
newsreaders and two domain addresses (rock.com & ock.com). With all
the forgeries in this group it's easy to see how one might think your
posts are being made by more than one person.


Also, as far as you know, n8wwm doesn't even post here.

Steveo wrote:
Frank Gilliland wrote:
On Wed, 29 Dec 2004 13:37:17 GMT, Lancer wrote in
htb5t058gbfee852kcbtht6vcul2jud5lu@2355323778:

snip
Ok Lancer (whichever one you are);


The same Lancer that has been here all along..

In your headers I saw several different servers, two different
newsreaders and two domain addresses (rock.com & ock.com). With all
the forgeries in this group it's easy to see how one might think your
posts are being made by more than one person.


Also, as far as you know, n8wwm doesn't even post here.

I forgot the smiley face. :-)

Jay in the Mojave wrote:
The boat had two engines and each engine had 2 alternators.

Must of had one of those big radios. Did he have an I 10-K on it too?

On Wed, 29 Dec 2004 17:55:16 -0600, itoldyouiamnotiamnotgeorge
wrote in
:

Frank Gilliland wrote in
:

Current equalizing resistors is another way to do it. It's common
practice in SS audio amps to use emitter resistors to equalize the
currents between parallel transistors. But I would hesitate using them
with modern alternators because I don't know how it would screw with
the regulators -- some have a local sense line and others have a
remote sense line -- a resistor in the load might send the regulator
into seizures.


Frank it is very easy a single regulator will control the field voltage on
both alternators. This way they would run the same and share the "Load"


I thought about that, but wouldn't the rotors need to be locked in
phase?

itoldyouiamnotiamnotgeorge
wrote:
-snip-
Hey Geo, what do you think of Kevin Millwood? The Tribe may sign him
to a one year deal.