1530

Item 1530

DESIGN: Electrotor-SloMo ~ Motor - Rotor - Permanent Magnet

Preliminary Specifications:

Also see; ElectrotorSloMo ~ Motor - Specifications

Magnetic Arc:	13.4	deg.
Energy Product:
Remeance:		KG
Magnets
Coercivity:		Koe

Notes on CSIRO/UTS Aurora:

Halbach array.

"The magnet selected was VAC362HR, a neodymium iron boron material, with B_r=1.33 T at 20°C" [DESIGN?]

"The team fabricated each pole from a set of four magnets, using a wire saw to form the NdFeB material to create a correctly-shaped magnetic field. With 40 poles and four magnets per pole, a total of 320 individual pieces of magnet are required."

Notes:

It appears from testing that two magnets, which are serially touching, have a similar strength as one magnet with a length equal to the sum of the two magnets.

Inserting cardboard (airgap) between the two magnets and between the lower magnet and an iron block does reduce the magnetic attraction, however the magnets still provide good lift.

When a stack consisting of; magnet, magnet, steel is pulled apart, the 'brake' comes between the magnet and the steel.

Does an iron cap on one pole change the magnetism at the other pole? It appears that having some iron on one pole may increase the magnetic attraction at the other pole.

The book [Axial Flux Permanent Magnet Brushless Machines] says "NdFeB PM can now be purchased in the Far East for less than US $20 per kilogram."

Material:

NdFeB ~ There are different grades.

Halbach Array:

This looks interesting but it appears that it may only be workable for the rotor - stator - rotor configuration.

Halbach magnet array; ~

http://www.tip.csiro.au/Machines/papers/iwscem/index.html

Build a Halbach array; http://www.matchrockets.com/ether/halbach.html - http://www.otherpower.com/danf/halbach.html

MAGNETIC FORCES INSIDE PERMANENT MAGNET ASSEMBLIES ~ http://www-sldnt.slac.stanford.edu/nlc/notes/Bowden_Eng/ABC_TechNote-067_2.pdf Have hard copy.

The Aurora - Solar-powered electric vehicle had an ironless air-gap winding.

Definition;~ http://en.wikipedia.org/wiki/Halbach_array Have hard copy.

http://www.gaussboys.com/pages.php?pageid=6

Characteristics:

Br is the measure of its residual magnetic flux density in Gauss, which is the maximum flux the magnet is able to produce. ( 1Gauss is like 6.45 lines/sq in)
Hc is the measure of the coercive magnetic field strength in Oersted, or the point at which the magnet becomes demagnetized by an external field. ( 1Oersted is like 2.02 ampere-turns/inch)
BHmax is a term of overall energy density. The higher the number, the more powerful the magnet.
Tcoef of Br is the temperature coefficient of Br in terms of % per degree Centigrade. This tells you how the magnetic flux changes with respect to temperature. -0.20 means that if the temperature increases by 100 degrees Centigrade, its magnetic flux will decrease by 20%!
Tmax is the maximum temperature the magnet should be operated at. After the temperature drops below this value, it will still behave as it did before it reached that temperature (it is recoverable).
Tcurie is the Curie temperature at which the magnet will become demagnetized. After the temperature drops below this value, it will not behave as it did before it reached that temperature. If the magnet is heated between Tmax and Tcurie, it will recover somewhat, but not fully (it is not recoverable).
(please note that this data is from www.magnetsales.com)

Material	Br	Hc	BHmax	Tcoef of Br	Tmax	Tcurie
NdFeB	12,800	12,300	40	-0.12	150	310
SmCo	10,500	9,200	26	-0.04	300	750
Alnico	12,500	640	5.5	-0.02	540	860
Ceramic or Ferrite	3,900	3,200	3.5	-0.20	300	460

BUY ~ Suppliers:

Stanford Magnets Company.

China Rare Earth Permanent Magnet Ltd.

Permanent Magnet Products; http://www.stanfordmagnets.com/magnet.html

NdFeB: (Neodymium, Iron and Boron) http://www.magnetsales.com/Neo/Neoprops.htm

Related Page ~ This Site:

OTHER: Electrical - General

Last Revised: June 7, 2009