MOEPED #3 is mechanically stable and more than half of the onboard 110 VAC
systems are on line.

MOEPED stands for MObile Experimental Physics Educational Demonstrator. It's
my project for one repeated credit at the community college Seminar and
Project in physics, PHY 298, with Dr. Majewski. It is a 2004 Lightning Cycle
Dynamics (www.lightningbikes.com) Thunderbolt recumbent, their base 7-speed
model, with several transmission changes.

First, there is the tandem crankset. Providing a 51 tooth cog on the left
side lets me drive a modified Surplus Center (www.surpluscenter.com) 10-1134
"impedance protected" (stall proof) ceiling fan motor with bike chain at
about its design rpm, or drive the pedals from the motor. Driving the pedals
from the motor helps debug the wide-range 24-35-51 / 11-34 gearing. Driving
the motor from the pedals should produce AC when patched correctly but it
doesn't and that is what this post is about. Pics are at
ftp://users.aol.com/DGoncz/Bicycle/ACMotorGenerator/

Second, the rear hub has been replaced and relaced with an 8 speed disc hub,
7 cogs, a spacer, and a Big Cheese spider to carry chain rings on the left
side. A 48 tooth cog drives an Ametek servo motor from C&H sales
(www.candhsales.com) rated 30 VDC, 12 A stall, 900 rpm, which drives a Radio
Shack inverter (www.radioshack.com) rated 140 W, 10-15 VDC, 2.4 W idle. The
pinion is 8 teeth, comes from Northern Hydraulic, who I think are at
(www.northerntool.com) and has been thinned to 2 mm and chamfered. The motor
mount is made from plastic drain pipe, hangs from the seat stay clamps, and
is tensioned from the seat brace. An aluminum motor mount is in the works.

The bike has been fitted with an ESGE dual leg kick stand, *backwards*.
Lighning has accepted this recommendation for their customer tip file. I
have not seen it in print. The bike stands on its own, and a bit of wood
underneath with two pocket holes captures the legs when you want to pedal
and prevents spreading of the kickstand legs. Two extra long spokes will soo
n be fitted to the stand legs to snag the chain stays with the spoke heads,
and wing nuts will tighten the spokes to lock the stand, allowing seated
pedaling. It will take five minutes to set up once parked.

To proof the power generating ability of the system I plugged the motor into
the inverter and went for a ride. As expected, it was a dynamic brake, but
nothing blew up. The system could generate say 20 watts all night long while
riding and you'd hardly notice it. I've run a fluorescent lamp from the
inverter. I could run my laptop from it but I don't have a padded case yet.

My question to the readers of alt.engineering.electrical,
rec.crafts.metalworking, sci.electronics.design, and sci.electronics.repair
is:

Given this is an impedance protected ceiling fan motor with many turns of
fine wire, and I have invested four years of effort, and the system is
stable, is it now time to rewind the stator with fewer turns of thicker wire
to optimize generator function, as it is not likely that this motor will
ever be stalled, or should I continue to try various cap combinations,
driving the AC motor/generator from the DC motor in reverse, or should I run
a sweep to find out what is going on and *compute* an optimized cap? I'm
leaning toward rewinding the stator. It seems like an idiot proof motor
would make a lousy generator.

The motor run cap is currently 5 microfarads. The self-excitation cap is
currently 30 microfarads. Currently the motor runs right as a motor, but
only generates 0.1 VAC at best speed when patched as a generator, even when
I "whack" it with DC while cranking as described in Lindsay's "Alternator
Secrets". I suspect there's just too many turns of wire in there. I have an
audio amp and can download Daqarta again for a sweep. I have a Tek 541 scope
with CA plug in. Soon all these and the bike will be under one roof.

Yours,

Doug Goncz
Replikon Research
Seven Corners, VA 22044-0394

There are not too many turns in it, in reality (despite theory) an
asynchronous motor cannot be a generator.Sorry to be the messenger of bad
news, but that's it.That's a reason why (I think so) wind-generators coupled
to the grid in fact work as motors, dissipating power than producing it as
generators.To produce ac, you need a *synchronous generator*, found
everywhere from small heads (650 W) to the largest one, 2000 MVA, operated
in a nuclear power station.Or, a dc *generator* (not motor).Either with
shunt, series or compound excitation.Usually it's shunt.

--
Tzortzakakis Dimitriïs
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
Ï "DGoncz 22044-0394" Ýãñáøå óôï ìÞíõìá
news:Gkdxd.4212$Qk5.104@lakeread04...
MOEPED #3 is mechanically stable and more than half of the onboard 110 VAC
systems are on line.

MOEPED stands for MObile Experimental Physics Educational Demonstrator.
It's
my project for one repeated credit at the community college Seminar and
Project in physics, PHY 298, with Dr. Majewski. It is a 2004 Lightning
Cycle
Dynamics (www.lightningbikes.com) Thunderbolt recumbent, their base
7-speed
model, with several transmission changes.

First, there is the tandem crankset. Providing a 51 tooth cog on the left
side lets me drive a modified Surplus Center (www.surpluscenter.com)
10-1134
"impedance protected" (stall proof) ceiling fan motor with bike chain at
about its design rpm, or drive the pedals from the motor. Driving the
pedals
from the motor helps debug the wide-range 24-35-51 / 11-34 gearing.
Driving
the motor from the pedals should produce AC when patched correctly but it
doesn't and that is what this post is about. Pics are at
ftp://users.aol.com/DGoncz/Bicycle/ACMotorGenerator/

Second, the rear hub has been replaced and relaced with an 8 speed disc
hub,
7 cogs, a spacer, and a Big Cheese spider to carry chain rings on the left
side. A 48 tooth cog drives an Ametek servo motor from C&H sales
(www.candhsales.com) rated 30 VDC, 12 A stall, 900 rpm, which drives a
Radio
Shack inverter (www.radioshack.com) rated 140 W, 10-15 VDC, 2.4 W idle.
The
pinion is 8 teeth, comes from Northern Hydraulic, who I think are at
(www.northerntool.com) and has been thinned to 2 mm and chamfered. The
motor
mount is made from plastic drain pipe, hangs from the seat stay clamps,
and
is tensioned from the seat brace. An aluminum motor mount is in the works.

The bike has been fitted with an ESGE dual leg kick stand, *backwards*.
Lighning has accepted this recommendation for their customer tip file. I
have not seen it in print. The bike stands on its own, and a bit of wood
underneath with two pocket holes captures the legs when you want to pedal
and prevents spreading of the kickstand legs. Two extra long spokes will
soo
n be fitted to the stand legs to snag the chain stays with the spoke
heads,
and wing nuts will tighten the spokes to lock the stand, allowing seated
pedaling. It will take five minutes to set up once parked.

To proof the power generating ability of the system I plugged the motor
into
the inverter and went for a ride. As expected, it was a dynamic brake, but
nothing blew up. The system could generate say 20 watts all night long
while
riding and you'd hardly notice it. I've run a fluorescent lamp from the
inverter. I could run my laptop from it but I don't have a padded case
yet.

My question to the readers of alt.engineering.electrical,
rec.crafts.metalworking, sci.electronics.design, and
sci.electronics.repair
is:

Given this is an impedance protected ceiling fan motor with many turns of
fine wire, and I have invested four years of effort, and the system is
stable, is it now time to rewind the stator with fewer turns of thicker
wire
to optimize generator function, as it is not likely that this motor will
ever be stalled, or should I continue to try various cap combinations,
driving the AC motor/generator from the DC motor in reverse, or should I
run
a sweep to find out what is going on and *compute* an optimized cap? I'm
leaning toward rewinding the stator. It seems like an idiot proof motor
would make a lousy generator.

The motor run cap is currently 5 microfarads. The self-excitation cap is
currently 30 microfarads. Currently the motor runs right as a motor, but
only generates 0.1 VAC at best speed when patched as a generator, even
when
I "whack" it with DC while cranking as described in Lindsay's "Alternator
Secrets". I suspect there's just too many turns of wire in there. I have
an
audio amp and can download Daqarta again for a sweep. I have a Tek 541
scope
with CA plug in. Soon all these and the bike will be under one roof.

Yours,

Doug Goncz
Replikon Research
Seven Corners, VA 22044-0394

There are not too many turns in it, in reality (despite theory) an
asynchronous motor cannot be a generator.Sorry to be the messenger of bad
news, but that's it.That's a reason why (I think so) wind-generators coupled
to the grid in fact work as motors, dissipating power than producing it as
generators.

???

Most grid connected large windmills use induction motor/generators as a simple
and inexpensive way to generate power. I worked for one of the companies in the
Altamont Pass in California who had about 1800 100 KW machines by the time I
left. It is quite impressive watching those power meters turn in the 'correct'
direction when the machine comes on line.

Earle Rich
Mont Vernon, NH

Asynchronous motor CAN be a generator...
It must turn faster than the magnetic field and you may apply some power
to it, then it will transfer power back to source...

Dimitrios Tzortzakakis wrote:
There are not too many turns in it, in reality (despite theory) an
asynchronous motor cannot be a generator.Sorry to be the messenger of bad
news, but that's it.That's a reason why (I think so) wind-generators coupled
to the grid in fact work as motors, dissipating power than producing it as
generators.To produce ac, you need a *synchronous generator*, found
everywhere from small heads (650 W) to the largest one, 2000 MVA, operated
in a nuclear power station.Or, a dc *generator* (not motor).Either with
shunt, series or compound excitation.Usually it's shunt.

--
Tzortzakakis Dimitriïs
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
Ï "DGoncz 22044-0394" Ýãñáøå óôï ìÞíõìá
news:Gkdxd.4212$Qk5.104@lakeread04...

MOEPED #3 is mechanically stable and more than half of the onboard 110 VAC
systems are on line.

MOEPED stands for MObile Experimental Physics Educational Demonstrator.

It's

my project for one repeated credit at the community college Seminar and
Project in physics, PHY 298, with Dr. Majewski. It is a 2004 Lightning

Cycle

Dynamics (www.lightningbikes.com) Thunderbolt recumbent, their base

7-speed

model, with several transmission changes.

First, there is the tandem crankset. Providing a 51 tooth cog on the left
side lets me drive a modified Surplus Center (www.surpluscenter.com)

10-1134

"impedance protected" (stall proof) ceiling fan motor with bike chain at
about its design rpm, or drive the pedals from the motor. Driving the

pedals

from the motor helps debug the wide-range 24-35-51 / 11-34 gearing.

Driving

the motor from the pedals should produce AC when patched correctly but it
doesn't and that is what this post is about. Pics are at
ftp://users.aol.com/DGoncz/Bicycle/ACMotorGenerator/

Second, the rear hub has been replaced and relaced with an 8 speed disc

hub,

7 cogs, a spacer, and a Big Cheese spider to carry chain rings on the left
side. A 48 tooth cog drives an Ametek servo motor from C&H sales
(www.candhsales.com) rated 30 VDC, 12 A stall, 900 rpm, which drives a

Radio

Shack inverter (www.radioshack.com) rated 140 W, 10-15 VDC, 2.4 W idle.

The

pinion is 8 teeth, comes from Northern Hydraulic, who I think are at
(www.northerntool.com) and has been thinned to 2 mm and chamfered. The

motor

mount is made from plastic drain pipe, hangs from the seat stay clamps,

and

is tensioned from the seat brace. An aluminum motor mount is in the works.

The bike has been fitted with an ESGE dual leg kick stand, *backwards*.
Lighning has accepted this recommendation for their customer tip file. I
have not seen it in print. The bike stands on its own, and a bit of wood
underneath with two pocket holes captures the legs when you want to pedal
and prevents spreading of the kickstand legs. Two extra long spokes will

soo

n be fitted to the stand legs to snag the chain stays with the spoke

heads,

and wing nuts will tighten the spokes to lock the stand, allowing seated
pedaling. It will take five minutes to set up once parked.

To proof the power generating ability of the system I plugged the motor

into

the inverter and went for a ride. As expected, it was a dynamic brake, but
nothing blew up. The system could generate say 20 watts all night long

while

riding and you'd hardly notice it. I've run a fluorescent lamp from the
inverter. I could run my laptop from it but I don't have a padded case

yet.

My question to the readers of alt.engineering.electrical,
rec.crafts.metalworking, sci.electronics.design, and

sci.electronics.repair

is:

Given this is an impedance protected ceiling fan motor with many turns of
fine wire, and I have invested four years of effort, and the system is
stable, is it now time to rewind the stator with fewer turns of thicker

wire

to optimize generator function, as it is not likely that this motor will
ever be stalled, or should I continue to try various cap combinations,
driving the AC motor/generator from the DC motor in reverse, or should I

run

a sweep to find out what is going on and *compute* an optimized cap? I'm
leaning toward rewinding the stator. It seems like an idiot proof motor
would make a lousy generator.

The motor run cap is currently 5 microfarads. The self-excitation cap is
currently 30 microfarads. Currently the motor runs right as a motor, but
only generates 0.1 VAC at best speed when patched as a generator, even

when

I "whack" it with DC while cranking as described in Lindsay's "Alternator
Secrets". I suspect there's just too many turns of wire in there. I have

an

audio amp and can download Daqarta again for a sweep. I have a Tek 541

scope

with CA plug in. Soon all these and the bike will be under one roof.

Yours,

Doug Goncz
Replikon Research
Seven Corners, VA 22044-0394

--
Tzortzakakis Dimitri?s
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
? "klasspappa[remove]" ?????? ??? ??????
news
Asynchronous motor CAN be a generator...
It must turn faster than the magnetic field and you may apply some power
to it, then it will transfer power back to source...

I just run through the book of electrical machines I, one of my old
subjects, and it doesn't mention asynchronous generators at all.It only
mentions alternators.If one generator needs applying power to it to generate
electricity, it loses the purpose of being a generator.The proof of this is
our friend's experience;in his post he mentions the asynchronous motor when
operated as a generator has an output of only 0.1 V RMS, which is useless
for any purpose at all.In no lab have we had a project of converting a motor
to a generator;always in motors and generators the apparatus was
separate.Talking about asynchronous generators.

"Dimitrios Tzortzakakis" wrote in
message ...


--
Tzortzakakis Dimitri?s
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
? "klasspappa[remove]" ?????? ???
??????
news
Asynchronous motor CAN be a generator...
It must turn faster than the magnetic field and you may apply some power
to it, then it will transfer power back to source...

I just run through the book of electrical machines I, one of my old
subjects, and it doesn't mention asynchronous generators at all.It only
mentions alternators.If one generator needs applying power to it to
generate
electricity, it loses the purpose of being a generator.

Then you need to find another book. An asyncrhonous generator needs an
external source for reactive power / excitation. That is not the same as
'applying power to it to generate'. When properly excited, an asyncrhonous
generator can supply much more power to the electrical system than it draws
in excitation energy. Much like a large synchronous machine needs an
external supply to its field to operate, yet it results in a net input of
power to the electrical system.

The proof of this is
our friend's experience;in his post he mentions the asynchronous motor
when
operated as a generator has an output of only 0.1 V RMS, which is useless
for any purpose at all.

Because 'our friend' didn't supply an external excitation. A synchronous
machine with an electromagnet field (not permanent magnets) also outputs
very low voltage when spinning with no DC field current. Are you suggesting
that synchronous machines are 'useless for any purpose at all'? Of course
not. Yet you suggest that an *improperly operated* asyncrhonous machine is
proof that all such machines are 'useless'.

In no lab have we had a project of converting a motor
to a generator;always in motors and generators the apparatus was
separate.Talking about asynchronous generators.


Possibly because your lab just didn't bother to explore this area. An
async. generator operating in a stand-alone fashion has many drawbacks. The
voltage control is difficult unless you have either a wound-rotor machine
and control the rotor circuit resistance, or variable capacitance connected
to the line terminals.

Because of the torque/slip characteristics of induction machines, the output
frequency is also very difficult to control. If the prime mover speed is
held constant, the output frequency varies with the amount of real load and
the amount of slip (remember in an async. generator, the output frequence is
lower than rotor speed. To maintain the output frequency in a stand-alone
machine, you must increase the rotor speed as load is applied.

But, if the machine is connected to a 'stiff' grid that approaches the
theoretical 'infinite bus', then many of these issues fade. The bus
maintains a constant frequency and voltage and the real power output of the
machine is controlled by controlling the speed of the prime mover. As speed
is increased above the synchronous speed of the machine, more power is
supplied to the bus.

Work out how the torque and power vs speed curves of an induction motor
behave and simply extrapolate beyond the synch. speed.

daestrom

On Tue, 21 Dec 2004 16:25:34 +0200, "Dimitrios Tzortzakakis"
wrote:

You know, posting that hyphen at the beginning of your post causes
everything below it to be *not quoted* in replies as if it were a
signature block.

What didn't get quoted:
*********
I just run through the book of electrical machines I, one of my old
subjects, and it doesn't mention asynchronous generators at all.It
only
mentions alternators.If one generator needs applying power to it to
generate
electricity, it loses the purpose of being a generator.
*********

Now think about that. I don't care if it's a "generator" or
"alternator". My alternator uses 12 V from the battery to suply
field magnetization.

The alternator puts out more electrical power than it consumes. Gee,
I wonder if that extra energy comes from the mechanical energy
driving it.


-
Best Regards,
Mike

"Dimitrios Tzortzakakis" wrote in
message ...
If one generator needs applying power to it to generate
electricity, it loses the purpose of being a generator.

Hardly; you can make a pretty good case that the most efficient generators
often DO require some external power for the sake of field excitation,
monitoring/control equipment, etc. This initially comes from a bank of
batteries, a smaller 'starter' generator where you don't care about
efficiency since it'll only be used briefly, etc.

I was talking to a guy here in Oregon whose job is to maintain and monitor a
small (a half dozen or so MW, I believe) hydroelectric power plant; one of
the points he took pride in was that at _his_ plant he still had enough
equipment around that he could get the plant going without any external
power whatsoever. He said that many plants have been 'modernized' such that
almost all of the control is computerized these days, but the downside is
that they require external grid power to get the main generator going at
all. I can see that being a defensible engineering choice, although if I
had the guy's job I'd also be a little more comfortable knowing I could
re-start from an off-grid condition.

---Joel Kolstad

"Joel Kolstad" wrote in message
...
"Dimitrios Tzortzakakis" wrote in
message ...
If one generator needs applying power to it to generate
electricity, it loses the purpose of being a generator.

Hardly; you can make a pretty good case that the most efficient generators
often DO require some external power for the sake of field excitation,
monitoring/control equipment, etc. This initially comes from a bank of
batteries, a smaller 'starter' generator where you don't care about
efficiency since it'll only be used briefly, etc.

I was talking to a guy here in Oregon whose job is to maintain and monitor
a small (a half dozen or so MW, I believe) hydroelectric power plant; one
of the points he took pride in was that at _his_ plant he still had enough
equipment around that he could get the plant going without any external
power whatsoever. He said that many plants have been 'modernized' such
that almost all of the control is computerized these days, but the
downside is that they require external grid power to get the main
generator going at all. I can see that being a defensible engineering
choice, although if I had the guy's job I'd also be a little more
comfortable knowing I could re-start from an off-grid condition.

In the industry, we say such a plant is 'capable of a black startup'. As
you say, many power plants today are *not* capable of starting up without
some external power. During the north-east blackout of 8/4/2003, one of the
priorities for the few plants that remained on-line was to supply power to
other plants so they could start up again. Many steam plants are not 'black
startup' capable as the myriad of circulating pumps and valves have to be
running before you can start rolling the turbine. Peaking plants such as
gas turbine or diesel often are capable of a 'black startup'.

I can certainly see how a hydro plant would be capable.

daestrom

"Ignoramus29457" wrote in message
...
I am confused about something. Even if a power plant requires external
power to start (say, fuel pumps should be operating for some time
before water heats up and boils), it would require a lot less power
than it produces. Probably many many times less. If so, then a power
plant can buy a generator of adequate size, say 1000 kW. It should
cost a relatively minuscule amount compared to the cost of the power
plant itself.

This is completely analogous to having an electric starter on an
engine. A small, cheap piece that can get stuff moving before the main
power plant starts up in a self sustained mode.

So, just what is the problem?Have them buy adequate generators and
that's all.

Any clarification will be appreciated.

i

They certainly could, however I think the issue is simply not wanting to
devote the money and space to a standby generator that might never be used
in the life of the plant. Not to mention maintenance of it, if a diesel
backup generator sits doing nothing for 25 years chances are it'll do
nothing right when it's needed most. I would still think it a good idea to
have one around, but I can see the resons for not having it.

On Sun, 19 Dec 2004 06:09:01 -0500, "DGoncz 22044-0394"
wrote:


Given this is an impedance protected ceiling fan motor with many turns of
fine wire, and I have invested four years of effort, and the system is
stable, is it now time to rewind the stator with fewer turns of thicker wire
to optimize generator function,

Yes. "Impedance protected" means the motor is mostly inductive at
any rotor speed from nominal to stall. If greatly reducing rotor
speed doesn't greatly increase load current, then raising speed won't
produce much useful power.

A way to think of an induction motor run above synch speed is as a
negative resistance. At nominal speed with mechanical load, it
draws both inductive current for excitation and "real" or resistive
current in phase with the line voltage. The latter is "real" power,
some or most of which is converted to mechanical power -- torque *
speed. If spun at synch speed, the motor would like like nearly a
pure inductance. If spun above synch speed, the "real" current will
be out of phase with the applied voltage so it acts as a negative
resitance, consuming negative power i.e. pumping power back toward
the excitation source that can then be dissipated by other loads.

Hey, everybody. I've been watching patiently for some time now.

"Don Foreman" wrote in message
...
On Sun, 19 Dec 2004 06:09:01 -0500, "DGoncz 22044-0394"
wrote:


Given this is an impedance protected ceiling fan motor with many turns of
fine wire, and I have invested four years of effort, and the system is
stable, is it now time to rewind the stator with fewer turns of thicker
wire
to optimize generator function,

Yes. "Impedance protected" means the motor is mostly inductive at
any rotor speed from nominal to stall. If greatly reducing rotor
speed doesn't greatly increase load current, then raising speed won't
produce much useful power.

You know, I missed the 17 bus from Little River Turnpike the other night
because the 29, which pulled to a stop right in front of it, had its banner
display out of order. So the 17 figured I was getting on the 29, not
stopping anxiously to ask, "Are you by any chance a 17, and do you know if
the bus behind you is?" Phhtt. I went and had turkey breast, peppers, and
horseradish.

One of the things I check for when I go to little shops like Quizno's is
whether they have tap water or carbonated at the fountain. I was in luck.
They had carbonated. Cheered, I called Teri on the mobile phone, and we went
and set up the repaired fax machine at Mom's after looking at Wild West Tech
on the History Channel for five minutes. I normally don't look at
television.

Don's reply is the sparkling water on this thread. Of course! If the torque
curve isn't steep, the motor isn't stiff, and it'll be a lousy generator. I
get it.

Now, electrically, does this inline resistance damp a resonant condition in
the parallel L-C "tank"?

Off too bed....

Yours,

Doug Goncz
Replikon Research
Seven Corners, VA 22044-0394

"Ignoramus29457" wrote in message
...
I am confused about something. Even if a power plant requires external
power to start (say, fuel pumps should be operating for some time
before water heats up and boils), it would require a lot less power
than it produces. Probably many many times less. If so, then a power
plant can buy a generator of adequate size, say 1000 kW. It should
cost a relatively minuscule amount compared to the cost of the power
plant itself.

This is completely analogous to having an electric starter on an
engine. A small, cheap piece that can get stuff moving before the main
power plant starts up in a self sustained mode.

So, just what is the problem?Have them buy adequate generators and
that's all.


Once a plant has started up, it certainly does produce more electricity than
it uses. A lot more. One plant I've worked at has a gross output of 880MW
electric. The 'hotel load' (the power needed to run the plant at full
power) is app. 30MW. So the net is 850MW.

But to start up, it needs about 15 - 20MW. And the main turbine is
producing zilch. Can you imagine how many diesel generator sets that would
take? A nice EMD V-16 can produce about 4MW. So, get about 5 or 6 of
those, connect them together with the correct switch-gear and controls and
have at it. But you will need this setup about once every 20 years, when a
major blackout such as 8/14/2003 occurs. That's a lot of hardware and
preventative maintenance for something you only need every 20 years. And 5
or 6 EMD V-16's with 4160V 4000kW output are not 'small, cheap pieces'.

So quite a lot of plants are not 'black startup' capable. The local grid
has to be 'up' to supply them with power to enable them to startup. Once
they *do* get on-line, it's a different story. But getting there is where
they need external power.

Take that nice diesel gen set you recently got. It's output is something
like 10kW right? And it just needs a nice 12V battery and electric starter
to get going. That's certainly affordable as opposed to a pull-rope. But
now imagine it scaled up by a factor of 100 000 so that you have a 1000MW
plant. In such a case even the 'cheap pieces' to start it would be very
expensive.

Some types of plants are much more easily made black start capable than
others. Hydro is perhaps the easiest. But even they need some
standby/emergency power for lubrication, gate-controls, cooling and such.
Modern gas turbines are probably also pretty easy to black-start. Steam
plants are some of the most demanding since they require a lot of pumping
power for the feed-water, and the boilers need quite a bit of auxilaries.

Then of course since most plants were built in the era of monopolistic
utilities with state regulation, you have to justify your plant's cost to
the regulators. The public service commission acknowledges that not *all*
the plants in a region need to be black start capable. They would not allow
such an 'extravagance' to be past on to the rate payers.

daestrom

"James Sweet" wrote in message
news:6%%xd.6574$L7.4717@trnddc05...
Not to mention maintenance of it, if a diesel
backup generator sits doing nothing for 25 years chances are it'll do
nothing right when it's needed most.

Aren't diesel backup generator typically exercised something like every week
or so for 15 minutes or somesuch in order to insure that they are ready when
actually needed?

"Joel Kolstad" wrote in message
...
"James Sweet" wrote in message
news:6%%xd.6574$L7.4717@trnddc05...
Not to mention maintenance of it, if a diesel
backup generator sits doing nothing for 25 years chances are it'll do
nothing right when it's needed most.

Aren't diesel backup generator typically exercised something like every
week or so for 15 minutes or somesuch in order to insure that they are
ready when actually needed?


Often it is a matter of past-performance. If they fail to start properly,
then the test frequency is increased. I've seen it as short as three days
on some really troublesome units. But if they perform well, then as
infrequent as once a month is common.

In addition to start tests, they are often 'load-tested' as well. The unit
is loaded to 100% and run for 3 hours or so to verify it can sustain full
load. This is done about quarterly. Or if the unit has been run unloaded
too much, they will be load tested in order to bring them up to full
temperature and burn out any soot problems. Depends on the unit.

daestrom

On Tue, 21 Dec 2004 22:05:27 -0500, "DGoncz 22044-0394"
wrote:

Now, electrically, does this inline resistance damp a resonant condition in
the parallel L-C "tank"?

Perhaps. "Impedance protected" simply means that the motor has enough
impedance so it will not overheat under locked rotor conditions. It's
more of a UL term than a technical descriptor. The impedance might
be due to stator resistance, rotor impedance and/or loose magnetic
coupling between stator and rotor. It is probably mostly reactive
because current flowing thru resistive impedance produces heat.

In fact, for brown coal fired plants I have visited this is 10%.For a 300 MW
the auxilliary circuits need 30 MW.It's impossible to have a generator that
size;there is a special transformer supplied from the 150 kV grid for
startup.So, without 150 kV grid -no startup.The generator itself supplies
the 400 kV grid (21kV/400 kV transformer).There was a hydro plant however,
that could be started with the 150 kV grid dead, by only a diesel generator
(here is where your idea comes) to open the valves for water.It has 3 125 MW
units;so is capable of supplying many brown coal plants at once.

--
Tzortzakakis Dimitriïs
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
Ï "Ignoramus29457" Ýãñáøå óôï ìÞíõìá
...
I am confused about something. Even if a power plant requires external
power to start (say, fuel pumps should be operating for some time
before water heats up and boils), it would require a lot less power
than it produces. Probably many many times less. If so, then a power
plant can buy a generator of adequate size, say 1000 kW. It should
cost a relatively minuscule amount compared to the cost of the power
plant itself.

This is completely analogous to having an electric starter on an
engine. A small, cheap piece that can get stuff moving before the main
power plant starts up in a self sustained mode.

So, just what is the problem?Have them buy adequate generators and
that's all.

Any clarification will be appreciated.

i

In fact, the plant "feeds its own auxilliary" as we were told;another
21kV/6.6 kV transformer takes power directly from the generator to feed
pumps, coal mills etc.Average power of 1 motor fed by 6.6 kV:1 MW.To
compare, a 30 MW generator with diesel engine prime mover is as large as a
mall.

--
Tzortzakakis Dimitriïs
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
Ï "James Sweet" Ýãñáøå óôï ìÞíõìá
news:6%%xd.6574$L7.4717@trnddc05...

"Ignoramus29457" wrote in message
...
I am confused about something. Even if a power plant requires external
power to start (say, fuel pumps should be operating for some time
before water heats up and boils), it would require a lot less power
than it produces. Probably many many times less. If so, then a power
plant can buy a generator of adequate size, say 1000 kW. It should
cost a relatively minuscule amount compared to the cost of the power
plant itself.

This is completely analogous to having an electric starter on an
engine. A small, cheap piece that can get stuff moving before the main
power plant starts up in a self sustained mode.

So, just what is the problem?Have them buy adequate generators and
that's all.

Any clarification will be appreciated.

i

They certainly could, however I think the issue is simply not wanting to
devote the money and space to a standby generator that might never be used
in the life of the plant. Not to mention maintenance of it, if a diesel
backup generator sits doing nothing for 25 years chances are it'll do
nothing right when it's needed most. I would still think it a good idea to
have one around, but I can see the resons for not having it.

Field excitation comes from a small dc generator coupled to the same shaft
as the alternator (usually 220 V-1000 A dc for a 300 MW altenator,21kV,
10kA).Usually it's shunt excitation.THAT'S a case where a generator
generates without external excitation;there is some remaining magnetism in
the stator of the dc generator, so when it rotates the voltage
increases..and increases.

--
Tzortzakakis Dimitriïs
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
Ï "Joel Kolstad" Ýãñáøå óôï ìÞíõìá
...
"Dimitrios Tzortzakakis" wrote in
message ...
If one generator needs applying power to it to generate
electricity, it loses the purpose of being a generator.

Hardly; you can make a pretty good case that the most efficient generators
often DO require some external power for the sake of field excitation,
monitoring/control equipment, etc. This initially comes from a bank of
batteries, a smaller 'starter' generator where you don't care about
efficiency since it'll only be used briefly, etc.

I was talking to a guy here in Oregon whose job is to maintain and monitor
a
small (a half dozen or so MW, I believe) hydroelectric power plant; one of
the points he took pride in was that at _his_ plant he still had enough
equipment around that he could get the plant going without any external
power whatsoever. He said that many plants have been 'modernized' such
that
almost all of the control is computerized these days, but the downside is
that they require external grid power to get the main generator going at
all. I can see that being a defensible engineering choice, although if I
had the guy's job I'd also be a little more comfortable knowing I could
re-start from an off-grid condition.

---Joel Kolstad