fixed coil/rotating magnet generator

[casrip1@gmx.com]

if you've seen my previous post, i talked about planning to make a small scale flywheel battery. to make this work with minimum energy loss, i plan to isolate the flywheel in a vacuumed chamber with magnetic or electrodynamic bearings.

 

in order to maintain high efficiency its important that no direct contact is made with the flywheel. so i plan to add magnets to the flywheel and put coils of wires around it. its kind of like a brushless motor, but in reverse; instead of the coil being at the center and a magnetic ring surrounding the coil, i will have a shaft with magnets in the middle that rotates and coils towards the outside.

 

- what i'm wondering is, will i need a controller like a brushless motor to charge/discharge the battery? and how exactly could i make this work?

[EdEarl]

Bearings and vacuum are only part of making an efficient electromechanical battery. You must also consider magnetic and electrical efficiency. Resistance in the wire used in motor-generator windings reduces efficiency. Current induced in the iron laminate used for electromagnets reduces efficiency. The phase angle between voltage and current in both motor and grid connection must be synchronized for greatest efficiency, which is made difficult because the grid phase angle changes continually.

 

 

Design of premium efficiency motors

 

Design of Premium Efficiency Motors needs special knowledge, experience and test facilities, equipped with precision instrumentation. The task of design is, to get the efficiency up by minimizing and balancing the single losses, especially those created in the stator coils, the stator iron (magnetizing) and the losses within the rotor by slip. In comparison to standard electrical motors compliant e.g. to IE1 for IE3 motor manufacturing, more iron and copper material are used. IE3 motors are heavier and physically bigger, than IE1 motors. Typically use of higher slot fill in the copper winding, use of thinner laminations of improved steel properties, reducing the air gap, better design of cooling fan, use of special and improved bearings etc. can ensure higher efficiency in the motors.

 

The high electrical conductivity of copper versus other metallic conductors enhances the electrical energy efficiency of motors.[10] Increasing the mass and cross section of copper in a coil increases the electrical energy efficiency of the motor. Copper motor rotors, a new technology designed for motor applications where energy savings are prime design objectives,[11][12] are enabling general-purpose induction motors to meet and exceed National Electrical Manufacturers Association (NEMA) premium efficiency standards.[13][14][15] For more information, see: Copper in energy efficient motors.

From: http://en.wikipedia.org/wiki/Premium_efficiency

 

[casrip1@gmx.com]

lol so i'd say its safe to assume that this summertime project is a tiny bit too big for a high school graduate?

[EdEarl]

It depends on the person, their knowledge, and their resources. It is unlikely an individual can make a motor-generator better than one bought, but not impossible. On the other hand, getting a fraction of a percent more efficiency might be very expensive. I do not know enough about where the inefficiencies occur to make such a judgement. I do know that General Electric has been making good motors since Steinmetz worked for them.

 

I believe a project of this nature has benefit, whether or not one makes one with improved efficiency, or even if one only studies the technology and does not build anything.

 

Generally motor electromagnets are laminated of soft iron plates with insulation between them to prevent eddy currents between plates. One might explore using soft iron square rods with insulation between them to reduce eddy currents. An ideal material would be one that did not conduct electricity but did conduct magnetism. Perhaps one could make a plastic with embedded iron filings to use as the magnetic conductor electric insulator. However, I do not know how much energy is lost in current laminates, so I do not know how much (if any) efficiency improvement is possible. Moreover, someone has probably thought of these ideas before and found them wanting.

 

Cryogenics might provide improved efficiencies via superconductivity, some research has been done on cryogenic motors. Such a design for an electromechanical battery could include magnetic bearings; that is, float the flywheel on a magnetic field. I suspect the cost of refrigeration reduces efficiency too much to be practical, but until someone does some research, perhaps does calculations, and maybe makes a working model, we will not know.

Edited June 20, 2013 by EdEarl

[Enthalpy]

Is it safe to assume that this summertime project is a tiny bit too big for a high school graduate?

If you ask whether a controller is necessary to rotate a brushless motor, yes, building the motor and the controller is to difficult for the moment.

 

Less difficult (but already difficult enough!), I'd suggest the vacuum aerostat

http://saposjoint.net/Forum/viewtopic.php?f=66&t=2520

accessible to a model airplane hobbyist.

 

Or the Pelton-Schaefer pump:

http://saposjoint.net/Forum/viewtopic.php?f=66&t=2272&start=10#p27829

http://saposjoint.net/Forum/viewtopic.php?f=66&t=2272&start=50#p33837

needs access to a milling machine.

 

Even more fun, reproduce the historic Fizeau-Foucault experiment

http://www.scienceforums.net/topic/16198-rpm-of-fizeau-foucault-apparatus/#entry752353

looks easy. It needs the proper light source and little more.

Edited June 20, 2013 by Enthalpy