Alternators, dc generators and alike

[sparkmen]

hi
is known the procedure to create electrical power by moving a coil through magnetic field or a magnetic field through coil, as dc generators or alternators.
all known or better said used procedures requires a mechanical work from which we calculate system efficiency.
what if we provide a moving magnetic field without using mechanical work, or better little mechanical work?
will there be something that will not suffice?
to me, the theory looks fine,according to present electricity laws.
pleased to hear .
rgds to all

[bistander]

hi
is known the procedure to create electrical power by moving a coil through magnetic field or a magnetic field through coil, as dc generators or alternators.
all known or better said used procedures requires a mechanical work from which we calculate system efficiency.
what if we provide a moving magnetic field without using mechanical work, or better little mechanical work?
will there be something that will not suffice?
to me, the theory looks fine,according to present electricity laws.
pleased to hear .
rgds to all

Hi sparkmen,
The magnetic field moves like you describe in a transformer, from one direction to the other with each cycle of the AC. And there will be a rotating magnetic field in a 3 phase synchronous or induction machine (motor or generator) at stall (no physical motion). Is that what you're looking for?
Regards,
bi

[sparkmen]

hi bi,
in transformers we have high/low on field.
i m thinking of an almost constant field in rotation ,like when you have permanent magnets creating the field , no high/low.
just that field rotated with very low mechanical power requirements
this way we expose induced coils to variable magnetic field and that is what creates the voltage.
rgds

[sparkmen]

for easy explanation and hope for easy understanding lets look into a car alternator:
-stator with output coils
-rotor with excitation coil, supplied by car battery.
to provide output on coils we need to turn rotor using mechanical power from engine . this way we expose the output coils to variable magnetic field. the more power taken from output, more mechanical power needed to rotate due to what is known as drag and other forces. But the excitation power required not vary much, more like instead of coil we have permanent magnets rotor

right up to here i guess.

[sparkmen]

now we take away the rotor and do something else.
from scrapyard we find a brushed motor with rotor that can fit to replace the old one, preferable with as many comutator segments as possible, remove old coils and make new ones as attached