Design consideration of magnets

In case if you haven't read the previous post linear/tubular generator please do (as it is the pt-2)

Magnets may be selected based on anticipated power generating necessities, cost considerations or a stability of cost and performance requirements. Optimum performance is obtained with magnets having high maximum energy product defined as the product of magnetizing force H times induction B. This property is essentially a measure of the efficiency of magnetic induction. Where cost considerations are a primary factor and generation capacity and power output is secondary, aluminum-nickel-cobalt or AlNiCo magnets may be employed. Alternatively, ceramic magnets such as barium or strontium ferrite may be used where increased power is desirable with marginal cost increases. Rare earth magnets may be preferred where cost is not a factor and maximum magnetic flux densities are required for maximum power generating capacity. For example, rare earth magnets such as samarium cobalt, SmCo₅ or S₂Co₁₇, or neodymium iron boron (“NdFeB”), for example Nd₂Fe₁₄B, may be employed to provide for high magnetic flux density.

In a preferred embodiment, magnets having a high “maximum energy product” B·H_max are used. The “maximum energy product” is defined as the point in the magnetic hysteresis loop at which the product of the magnetizing force H and induction B reaches a maximum. At this point, the volume of magnetic material required to project a given energy into its surroundings is at a minimum.

In a most preferred embodiment, neodymium iron boron magnets are employed due to their relatively high maximum energy product. NdFeB magnets with remanent magnetic flux density B_rem of 1.3 Tesla are widely available and magnets having a B_rem of 1.5 Tesla have been recently commercialized. In a preferred embodiment, rare earth magnets having a typical remanent magnetization B_rem and coercive magnetic field H_c of 1.5 Tesla are employed. Based on actual road profiles encountered under normal urban driving conditions, NdFeB magnets could potentially lead to power contribution efficiencies of at least 50% with the device.

A key design feature of the electromagnetic generator device may be in the unique configuration and orientation of stacked central magnets and spacers, stacked concentric magnets and spacers, coil location, and magnet magnetic pole orientations which provide for vector superposition of magnetic fields from a plurality of neighboring magnets to produce a maximum average radial magnetic flux density in the coil windings.

THE HALBACH ARRAY

fig 1

 NdFeB magnets or batter say neodymium maygnets are already strong but if we arrange it in a special manner called a halbach array, so normally we arrange from north to south symmetric on the both side of the magnets (fig 1) but if we rearrange the those magnets in this special halbach array, the magnetic feild lines are channeled almost entirely into oneside of the magnetic array and they cancel out on the other side(fig 2) 

fig 2

This configuration produces a much stronger magnetic field without changing the properties of the magnets. Also, this configuration mainly used in the particle accelerator, maglev trains and also ganna be used in hyperloop.