Re: Lorentz force

["lorikloesel" <lkloesel@xxxxxxxxxxxxx>]

I'm assuming that this shows up as a 120Hz vibration in a 60Hz 
driven system? The amplitude of the mechanical vibration is related to 
the mass of the object and the strength of the 2x force?

Thanks


--- In femm@xxxx, David Meeker <dmeeker@xxxx> wrote:
> mercedes sampere wrote:
> 
> > Hi femm users!
> > Could anybody tell me what does "2x frecuency force mean" when I 
ask for
> > Lorentz force?
> > Ex:
> > Steady-state force:
> > x-component: -3.027513e-002 N/m
> > y-component: -1.022735e-004 N/m
> > 2x Frequency force:
> > x-component: -3.011e-002 - j 9.877e-003 N/m
> > y-component: -1.059e-004 - j 5.189e-005 N/m
> >
> > Thank you very much
> > Mercedes.
> >
> 
> Well, force equals the integral of J X B. If you are evaluating a
> time-harmonic problem, current density J varies sinusoidally in 
time, and the
> resulting flux density B also varies sinusoidally in time, with both 
J and B
> oscillating at the same frequency. If you multiply together two 
sine waves,
> you get one portion that is constant with respect to time, and one 
portion
> that varies at twice the base frequency, e.g.:
> 
> Sin[t]^2 = (1 - Cos[2*t])/2
> 
> Therefore, since the force is the product of sinusoidally varying 
quantities,
> you get a constant component and a 2x component, and what femm is 
reporting
> is the net constant and 2x components. Part of the purpose of 
making 3 phase
> systems is so that the 2x components all cancel out, leaving only 
the part of
> force that is constant with respect to time.
> 
> Dave.