Magnetic circuit simulation request

[m II]

I have no experience using the programs available for finite element
analysis and don't have the time to learn how to use one.. If someone
experienced with their use could run a simulation, it would be of great
benefit.

I have a microwave oven transformer of 1000W rating.

I would like to remove the "I" part of the core, leaving the "E"
segment, along with the windings.

What I am interested in finding out is what happens when a permanent
magnet pole is moved past the centre leg of the core.

What is the change when a metallic return path to the back of the magnet
is provided? Think of a steel strip with the magnet in the centre. This
strip would sweep across the three legs of the core.

What change with a large disc magnet in the centre of the strip and two
smaller magnets with flipped polarities on the outer ends? I'm assuming
the air gaps remain the same.

Any units of comparison would be great, as it's the *relative* output
changes in the windings that I'm interested in. There has to be a way of
simulating this on the computer. I don't want to build the project in
real life until I can see some promise of success. This coil/core would
become 1/9 of a wind turbine alternator and be rectified for use.

One of those neat multicoloured flux flow graphics would be interesting.

mike

 

[Klaus Kragelund]

I have no experience using the programs available for finite element

analysis and don't have the time to learn how to use one.. If someone

experienced with their use could run a simulation, it would be of great

benefit.

Yes, nice to get free work. Why dont you just do the experiment?

I have a microwave oven transformer of 1000W rating.



I would like to remove the "I" part of the core, leaving the "E"

segment, along with the windings.



What I am interested in finding out is what happens when a permanent

magnet pole is moved past the centre leg of the core.

When it is open, the coupling is bad, so not much enery is transferred to the magnetron. Gradually when you slide the maget (which will transfer the flux) to fill the gap, you get 100% power to the magnetron.

The transformer does not care that you use permament mangnets, except if it would saturate, which it should not do, since it is a 50Hz transformer with high Bmax

If you only move past the center of the transformer leg, with a large airgap, nothinh happens. You need to bridge the gap

What is the change when a metallic return path to the back of the magnet

is provided? Think of a steel strip with the magnet in the centre. This

strip would sweep across the three legs of the core.

See above

What change with a large disc magnet in the centre of the strip and two

smaller magnets with flipped polarities on the outer ends? I'm assuming

the air gaps remain the same.


None


Any units of comparison would be great, as it's the *relative* output

changes in the windings that I'm interested in. There has to be a way of

simulating this on the computer. I don't want to build the project in

real life until I can see some promise of success. This coil/core would

become 1/9 of a wind turbine alternator and be rectified for use.

Skip the microwave oven transformer, and buy a car alternator. Cheaper, simpler and works

Cheers

Klaus

 

[Syd Rumpo]

I have no experience using the programs available for finite element
analysis and don't have the time to learn how to use one.. If someone
experienced with their use could run a simulation, it would be of great
benefit.

I have a microwave oven transformer of 1000W rating.

I would like to remove the "I" part of the core, leaving the "E"
segment, along with the windings.

What I am interested in finding out is what happens when a permanent
magnet pole is moved past the centre leg of the core.

What is the change when a metallic return path to the back of the magnet
is provided? Think of a steel strip with the magnet in the centre. This
strip would sweep across the three legs of the core.

What change with a large disc magnet in the centre of the strip and two
smaller magnets with flipped polarities on the outer ends? I'm assuming
the air gaps remain the same.

Any units of comparison would be great, as it's the *relative* output
changes in the windings that I'm interested in. There has to be a way of
simulating this on the computer. I don't want to build the project in
real life until I can see some promise of success. This coil/core would
become 1/9 of a wind turbine alternator and be rectified for use.

One of those neat multicoloured flux flow graphics would be interesting.

mike

There's a program called 'vizimag' which may be useful, I think you get
30 days free trial. Slightly annoying user interface, but graphical and
easy to use.

One thing to bear in mind is the permeability of the magnet - it may
come as a surprise (it did to me) that, for example, Neodymium magnets
have a very low relative permeability, not much more than air.

Cheers

 

[RobertMacy]

I have no experience using the programs available for finite element
analysis and don't have the time to learn how to use one.. If someone
experienced with their use could run a simulation, it would be of great
benefit.

I have a microwave oven transformer of 1000W rating.

I would like to remove the "I" part of the core, leaving the "E"
segment, along with the windings.

What I am interested in finding out is what happens when a permanent
magnet pole is moved past the centre leg of the core.

What is the change when a metallic return path to the back of the magnet
is provided? Think of a steel strip with the magnet in the centre. This
strip would sweep across the three legs of the core.

What change with a large disc magnet in the centre of the strip and two
smaller magnets with flipped polarities on the outer ends? I'm assuming
the air gaps remain the same.

Any units of comparison would be great, as it's the *relative* output
changes in the windings that I'm interested in. There has to be a way of
simulating this on the computer. I don't want to build the project in
real life until I can see some promise of success. This coil/core would
become 1/9 of a wind turbine alternator and be rectified for use.

One of those neat multicoloured flux flow graphics would be interesting.

mike

download free femm 4.2, join the group, ask there

 

[m II]

Yes, nice to get free work. Why dont you just do the experiment?

That hurts...

Skip the microwave oven transformer, and buy a car alternator. Cheaper, simpler and works

The field on the alternator I have takes about four amps at thirteen
volts. Losing 50 watts in lower winds is too inefficient.


mike

 

[m II]

It's a PWM system... 4 Amps is at full load.

...Jim Thompson

You are probably right, if the alternator was in a car. This one has
the field connections coming out and I vary the current through the
field. A short to ground gives maximum current. The other end of the
field winding is fed internally.

A permanent magnet rotor would be one solution, but there is another
drawback. Car alternators have to spin a lot faster than the blades on
a wind turbine. Once you get the gearing or pulleys sorted out, you've
just added another loss of power.

Those axial flow permanent magnet
alternators seem to be the best way to go, hence the search for
prebuilt coils. A built in core would be a bonus.

mike

 

[m II]

On Sun, 25 Aug 2013 13:18:31 -0700

Alternators with PM rotors, typically only seen on motorcycles,
"regulate" with a zener or shunt regulator.

I haven't seen a Zener used for direct regulation of output current on a
motorcycle since the sixties and early seventies. The english bikes had
them. Most modern bikes use three phase alternators with a regulated
field winding. Harley might still use a single phase permanent magnet
setup, but even they aren't dumb enough to use a shunt setup or Zener.

There is probably a valid reason to use a Zener inside the regulation
circuit as a voltage reference for some transistor base or FET or
something, but not as a direct dump to ground, as the English did.


mike

 

[josephkk]

On Sun, 25 Aug 2013 13:18:31 -0700

I haven't seen a Zener used for direct regulation of output current on a
motorcycle since the sixties and early seventies. The english bikes had
them. Most modern bikes use three phase alternators with a regulated
field winding. Harley might still use a single phase permanent magnet
setup, but even they aren't dumb enough to use a shunt setup or Zener.

There is probably a valid reason to use a Zener inside the regulation
circuit as a voltage reference for some transistor base or FET or
something, but not as a direct dump to ground, as the English did.


mike

I have no idea which bikes you are talking about, but every Honda and
Kawasaki bike i have owned had a shunt regultor. At least 6 models form
the 1980s to 2007 model years. I bought the service manuals for every
one.

?-)

 

[m II]

Then why aren't you PWM-ing your field current?

...Jim Thompson

I don't see any energy savings in pulsing the field instead of a steady
DC current. If the batteries need sixty amps, there has to be a set
current flow in the field. Any amount of pulsing would just serve to
reduce the total amount of 'below the curve' field current.

I see no difference in my alternator compared to a transformer, the
rotating primary being excepted, of course....and the resultant need for
a DC vs AC flow.

mike

 

[m II]

I have no idea which bikes you are talking about, but every Honda and
Kawasaki bike i have owned had a shunt regultor. At least 6 models
form the 1980s to 2007 model years. I bought the service manuals for
every one.

?-)

My understanding of 'shunt' may be at fault. The word to me means an
alternate path for the alternator output current to flow. The English
Zeners just dumped all the excess power to ground. They could do that
with 150 Lucas style watts.

To my perhaps misguided way of thinking, changing the field current to
regulate the output doesn't qualify as a shunt regulator.

Even on a permanent magnet Harley alternator, they have a series
regulation on the output, with no flow to ground.

Think of railway terminology. A shunt is a parallel path to the main track.

mike

 

[Robert Baer]

My understanding of 'shunt' may be at fault. The word to me means an
alternate path for the alternator output current to flow. The English
Zeners just dumped all the excess power to ground. They could do that
with 150 Lucas style watts.

To my perhaps misguided way of thinking, changing the field current to
regulate the output doesn't qualify as a shunt regulator.

Even on a permanent magnet Harley alternator, they have a series
regulation on the output, with no flow to ground.

Think of railway terminology. A shunt is a parallel path to the main track.

mike

Do not forget the frog..

 

[m II]

Do not forget the frog..

getting cross.....



mike

 

[josephkk]

My understanding of 'shunt' may be at fault. The word to me means an
alternate path for the alternator output current to flow. The English
Zeners just dumped all the excess power to ground. They could do that
with 150 Lucas style watts.

To my perhaps misguided way of thinking, changing the field current to
regulate the output doesn't qualify as a shunt regulator.

Even on a permanent magnet Harley alternator, they have a series
regulation on the output, with no flow to ground.

Think of railway terminology. A shunt is a parallel path to the main
track.

mike

Your understanding of shunt regulator is the same as mine. Every one
blew off as much watts as necessary, as the rotor was permanant magnets
(sometimes inside the crankcase oil bath region).

Gold Wings, most BMW MC and some other have proper fields coils and more
normal regulators. Far more typical is PM rotors and shunt regulators,
especially in smaller MC.

?-)

 

[josephkk]

I don't see any energy savings in pulsing the field instead of a steady
DC current. If the batteries need sixty amps, there has to be a set
current flow in the field. Any amount of pulsing would just serve to
reduce the total amount of 'below the curve' field current.

I see no difference in my alternator compared to a transformer, the
rotating primary being excepted, of course....and the resultant need for
a DC vs AC flow.

mike

Lordy. Even late 1950s Lucas generator relay regulators PWMed the
field. I didn't suspect that you didn't know.

?-)

 

[Fred Abse]

If the batteries need sixty amps, there has to be a set current
flow in the field

WRONG!

 

[m II]

WRONG!

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.

mike

 

[Klaus Kragelund]

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.

Suggested reading:

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


Regards

Klaus

 

[RobertMacy]

...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, 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.

 

[RobertMacy]

...snip...
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.

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?

 

[m II]

Lordy. Even late 1950s Lucas generator relay regulators PWMed the
field. I didn't suspect that you didn't know.

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