Pumblechook said:
Generators can't produce pure DC as from a battery.
It is actually rectified AC which has a ripple. It can be smoothed with chokes and capacitors.
With all due respect, while your statement that “generators can’t produce pure DC as from a battery” is in essence correct, your statement that “it is actually rectified AC which has a ripple” is patently incorrect.
DC generators require no form of rectification whatsoever nor do they produce a rectifiable AC voltage. While the rippling on top of the DC voltage is often referred to as an “AC component”, this is entirely different than an actual “AC generated voltage”. AC requires reversal of both voltage polarity and current direction, which clearly isn’t occurring per the output of a DC generator.
Rather ingeniously, the DC generator, via its multiple commutator segments pairs and associated multiple armature windings (wound at various degrees apart on the armature’s shaft) completely eliminates any need to rectify any AC voltage induced in any of the non-conducting armature windings. This is because only ONE armature winding is ever selected per a given orientation in the armature’s rotation making it the ONLY conductive armature winding capable of delivering current. Since this selected armature winding is always physically oriented within the same magnetic polar region of the stationary magnetic fields, the polarity of the voltage that will be induced will always be the same polarity hence, a DC voltage is generated per a given direction of the armature’s rotation.
It makes no difference that the non-conducting armature windings located prior and after this select magnetic polar region of the stationary magnetic fields will have some varying degree of an opposing polarity induced in them, as by the time these armature windings once again rotate around into the select magnetic polar region of the stationary magnetic fields, the voltage polarity induced in them will once again be of the same polarity hence, a DC voltage is generated whose peaks only ripple due to the variation in flux density of the stationary fields within the select and limited magnetic polar region in which voltage is to be induced.
Some technical explanations will misleadingly state that this technique of using multiple commutator segments and multiple armature windings constitutes a form of “mechanical rectification”, but this is as misleading as it is incorrect and here’s why.
In rectifying an AC voltage, the AC present allows current flow “in one direction only” through the load (via half wave rectification, current in both directions via full wave rectification, but in either case, a single polarity is established in the circuit) therefore, current from the AC source IS provided and energy dissipated by the load.
The DC generator’s ingenious arrangement of multiple commutator segments and multiple armature windings prevents ANY current from flowing from the non-conductive armature windings regardless of their induced voltage polarity or voltage potential. No actual AC rectification ever occurs nor is any form of rectification required.
