Magnetic circuit simulation request

[Phil Hobbs]

ARRRGGG! Why is the best way to discover the answer to ANY question is
to first pose it on the internet, embarrass oneself with stupidity, and
THEN see the solution!

ANSWER: The squirrel cage is BEST for working against head pressure and
the standard blade is best for 'free' flowing air.

Is that it?

A centrifugal blower the size of your average wind generator would be
quite the installation!

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

[Phil Hobbs]

I broke down and actually did some research. I was wrong. It would
appear that even in this enlightened era, there are such things as
'pulsating contacts' and dumping amperage to ground to divert it from
reaching the battery. Unbelievable.

My only excuse (and humble attempt to redeem myself) is that I live in a
small town and sometimes it takes decades for new information to reach
us. This year of 1972 is finding me in good health.


mike

Shorting out an alternator reduces the drag, so it isn't as bad as you'd
think. Heating a zener is another matter.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

[Fred Abse]

If the wind dictates that the rpm stays the same, the only other variable
is the field current. Rpm and field current are the only variables given
the same state of charge in the battery.

Field current controls output voltage, not output current, ergo your
original statement is incorrect.

Lead-acid batteries need a current-limited, constant voltage, charge.
Automobile alternators self-limit on current, and employ some sort of
feedback control of voltage by controlling field current. DC regulation
in earlier times, more efficient PWM, now. Most of the time, an automotive
alternator is supplying vehicle electrical loads, with only a small
proportion of its output going into the battery.

If only 'twere true that the wind dictated that the RPM stays the same.
Wind speed varies from minute to minute. A combination of inertia, and
careful blade design, even variable-pitch, and governors, are necessary
to ensure even approximately constant speed. At low RPM, and high field
excitation, the turbine might not supply enough torque to turn the
generator.

A battery designed for automotive starting service is quite different to
one designed for cyclic use. Look at the differing curves published by
battery manufacturers. Different constructions require different charging
profiles.

 

[Klaus Kragelund]

...snip....

Suggested reading:






Klaus

EXCELLENT! Thank you, Klaus.

Perhaps you can answer one question with regard to that paper's

discussion of temperature compensation. At high temperature, the voltage

to the battery is turned down to PREVENT the battery boiling over [that I

understand], but what I missed was any mention of the relationship between

the battery's voltage and temperature. Did I miss? What I mean is that

lead-acid battery's voltage drops with temperature, to something like 8

volts at low temps and climbs to something like 14+ V at high temp and

that effect would seem to help compensate for the other effect, that is

the battery cannot take as much 'power' at high temperature and can take

more 'power' at low temperature. However, the curve shown for temperature

compensation seemed a bit extreme without any inclusion of what the

battery is doing.





QUESTION in general: Why are wind generator blades shaped like giant

propellers and NOT squirrel cage shapes? From logic it would seem that

the best shape would be to follow what the fan makers discovered, that the

best transfer of energy occurs with the squirrel cage shape and not the

standard 'fan' shaped blades. Not being astute at fluidic energy transfer,

could not work this out for self.

Talking about wind turbines, some of the actually use what is called doublefed generators. The function is much like the alternator. A sine shaped field current determines the output from the generator. The output frequency of the generator is the difference of the shaft frequency and the rotor current frequency

Cheers

Klaus

 

[Tauno Voipio]

...snip....

Suggested reading:






Klaus

EXCELLENT! Thank you, Klaus.

Perhaps you can answer one question with regard to that paper's

discussion of temperature compensation. At high temperature, the voltage

to the battery is turned down to PREVENT the battery boiling over [that I

understand], but what I missed was any mention of the relationship between

the battery's voltage and temperature. Did I miss? What I mean is that

lead-acid battery's voltage drops with temperature, to something like 8

volts at low temps and climbs to something like 14+ V at high temp and

that effect would seem to help compensate for the other effect, that is

the battery cannot take as much 'power' at high temperature and can take

more 'power' at low temperature. However, the curve shown for temperature

compensation seemed a bit extreme without any inclusion of what the

battery is doing.





QUESTION in general: Why are wind generator blades shaped like giant

propellers and NOT squirrel cage shapes? From logic it would seem that

the best shape would be to follow what the fan makers discovered, that the

best transfer of energy occurs with the squirrel cage shape and not the

standard 'fan' shaped blades. Not being astute at fluidic energy transfer,

could not work this out for self.

Talking about wind turbines, some of the actually use what is called double fed generators. The function is much like the alternator. A sine shaped field current determines the output from the generator. The output frequency of the generator is the difference of the shaft frequency and the rotor current frequency

Cheers

Klaus

It is actually a classical mixing. You'll get both sum and difference of
the excitation and shaft frequencies.

 

[Klaus Kragelund]

On Thu, 29 Aug 2013 00:06:35 -0700, Klaus Kragelund




...snip....



Suggested reading:



http://www.embedded.com/design/embe...ontroller-driven-alternator-voltage-regulator





Regards



Klaus



EXCELLENT! Thank you, Klaus.

Perhaps you can answer one question with regard to that paper's

discussion of temperature compensation. At high temperature, the voltage

to the battery is turned down to PREVENT the battery boiling over [that I

understand], but what I missed was any mention of the relationship between

the battery's voltage and temperature. Did I miss? What I mean is that

lead-acid battery's voltage drops with temperature, to something like 8

volts at low temps and climbs to something like 14+ V at high temp and

that effect would seem to help compensate for the other effect, that is

the battery cannot take as much 'power' at high temperature and can take

more 'power' at low temperature. However, the curve shown for temperature

compensation seemed a bit extreme without any inclusion of what the

battery is doing.





QUESTION in general: Why are wind generator blades shaped like giant

propellers and NOT squirrel cage shapes? From logic it would seem that

the best shape would be to follow what the fan makers discovered, thatthe

best transfer of energy occurs with the squirrel cage shape and not the

standard 'fan' shaped blades. Not being astute at fluidic energy transfer,

could not work this out for self.

Talking about wind turbines, some of the actually use what is called double fed generators. The function is much like the alternator. A sine shaped field current determines the output from the generator. The output frequency of the generator is the difference of the shaft frequency and the rotorcurrent frequency

Cheers

Klaus

It is actually a classical mixing. You'll get both sum and difference of

the excitation and shaft frequencies.

Thanks, didn't know that (I was on a "need to know basis") ;-)

Cheers

Klaus

 

[Jasen Betts]

It is actually a classical mixing. You'll get both sum and difference of
the excitation and shaft frequencies.

only if the rotor is single-phase with a polyphase rotor you can do
SSB mixing and produce a single output frequency.


It seems that if the rotor leads the output frequency this would
generate energy in both the rotor windings.

 

[Jasen Betts]

Field current controls output voltage, not output current, ergo your
original statement is incorrect.

Field current puts a hard limit on output current.

Once the output current times the output turns count matches the
input current times the input turns count the magnetic field is
nulled and no voltage is produced.

 

[Fred Abse]

Field current puts a hard limit on output current.

Once the output current times the output turns count matches the input
current times the input turns count the magnetic field is nulled and no
voltage is produced.

Naturally. Below this limit, voltage is a function of field current.

Automotive alternators limit at tens of amps. Fine for a discharged
starting type battery with the lights on. Not so fine for batteries
designed for cyclic service.

The OP seems to want to stuff 60 amps into his batteries, irrespective of
state of charge. Not a good idea.

 

[Fred Abse]

It seems that if the rotor leads the output frequency this would generate
energy in both the rotor windings.

In a generator, the rotor phase always leads (torque angle) the (loaded) output
phase.

The same principle in reverse can be used to make an unloaded,
over-excited, synchronous motor look like a capacitor.

 

[[email protected]]

In a generator, the rotor phase always leads (torque angle) the (loaded) output
phase.

The same principle in reverse can be used to make an unloaded,
over-excited, synchronous motor look like a capacitor.

AKA synchronous capacitor; used for power factor correction.

 

[Fred Abse]

AKA synchronous capacitor; used for power factor correction.

That's the fella.

Some of the explanations I've seen beggar belief, Why is it that the power
engineering fraternity are so fond of vector diagrams?

It can be explained with half a dozen lines of complex algebra.