- #1
artis
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So while thinking about motors this suddenly struck me,
So as the universal series wound motor is spinning there is always some arcing going on around the place where the brushes contact the copper segments that slide past them, I assume this is at least partly because as each coil pair of the rotor is connected a current is built up in the coil , then as the segment for that coil pair passes by the brushes it disconnects electrically from the brushes at some point, this disconnection is rapid especially at higher RPM.
As much as I know from physics I have always remembered that an inductor always opposes changes in current , so upon sudden disconnection and circuit termination the inductor B field collapses inducing high voltage across it's terminals, this is the way car ignitions coils work I think.So here as the coil slots disengage the brushes in theory on those slots there is a voltage buildup due to the stored flux collapsing ?
But this energy left in the disengaged coil gets wasted right?
So what would happen if I took a universal motor and positioned additional brushes at some distance from the current providing ones? I should pickup some voltage/current as each disengaged slot pair passed my new set of brushes by ?
PS. Now that I think of it , could it be that at higher speeds the rotation of the rotor is fast enough that each disengaged coil pair doesn't have the time to fully collapse it's field and as it completes a full turn and touches the brushes again there is still some voltage left over from the last cycle in that coil ?
So as the universal series wound motor is spinning there is always some arcing going on around the place where the brushes contact the copper segments that slide past them, I assume this is at least partly because as each coil pair of the rotor is connected a current is built up in the coil , then as the segment for that coil pair passes by the brushes it disconnects electrically from the brushes at some point, this disconnection is rapid especially at higher RPM.
As much as I know from physics I have always remembered that an inductor always opposes changes in current , so upon sudden disconnection and circuit termination the inductor B field collapses inducing high voltage across it's terminals, this is the way car ignitions coils work I think.So here as the coil slots disengage the brushes in theory on those slots there is a voltage buildup due to the stored flux collapsing ?
But this energy left in the disengaged coil gets wasted right?
So what would happen if I took a universal motor and positioned additional brushes at some distance from the current providing ones? I should pickup some voltage/current as each disengaged slot pair passed my new set of brushes by ?
PS. Now that I think of it , could it be that at higher speeds the rotation of the rotor is fast enough that each disengaged coil pair doesn't have the time to fully collapse it's field and as it completes a full turn and touches the brushes again there is still some voltage left over from the last cycle in that coil ?