Goodness factor
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The goodness factor is a metric developed by Eric Laithwaite to determine the 'goodness' of an electric motor. Using it he was able to develop efficient magnetic levitation induction motors. : G = \frac {\omega} {\mathrm{resistance} \times \mathrm{reluctance}} = \frac {\omega \mu \sigma A_\mathrm{e} A_\mathrm{m}} {l_\mathrm{e} l_\mathrm{m}} where : is the goodness factor (factors above 1 are likely to be efficient) : , are the cross sections of the electric and magnetic circuits : , are the lengths of the electric and magnetic circuits : is the permeability of the core : is the angular frequency the motor is driven at : is the conductivity of the conductor From this he showed that the most efficient motors are likely to be relatively large. However, the equation only directly relates to non-permanent magnet motors. Laithwaite showed that for a simple induction motor this gave: : G \propto \frac {\omega \mu_0 p^2} {\rho_\mathrm{r} g} where is the pole pitch arc length, is the surface resistivity of the rotor and is the air gap.
The goodness factor is a metric developed by Eric Laithwaite to determine the 'goodness' of an electric motor. Using it he was able to develop efficient magnetic levitation induction motors. G = \frac {\omega} {\mathrm{resistance} \times \mathrm{reluctance}} = \frac {\omega \mu \sigma A_\mathrm{e} A_\mathrm{m}} {l_\mathrm{e} l_\mathrm{m}} where is the goodness factor (factors above 1 are likely to be efficient) , are the cross sections of the electric and magnetic circuits , are the lengths of the electric and magnetic circuits is the permeability of the core is the angular frequency the motor is driven at is the conductivity of the conductor From this he showed that the most efficient motors are likely to be relatively large. However, the equation only directly relates to non-permanent magnet motors. Laithwaite showed that for a simple induction motor this gave: G \propto \frac {\omega \mu_0 p^2} {\rho_\mathrm{r} g} where is the pole pitch arc length, is the surface resistivity of the rotor and is the air gap.
References
Text derived from https://en.wikipedia.org/w/index.php?oldid=1292765181 under CC BY-SA 4.0; modifications have been made.