What are 3 purposes of the split rings on the commutator? What is the difference between a DC and an AC motor? explain.
Well, you said split ring, not slip ring, if that was a typo, then you have already gotten some answers, but if it was not a typo and you really meant split ( like this; hyperphysics.phy-astr.gsu.edu/Hba... ) I can come up with two purposes, 1, to conduct current into the armature to create the magnetic field that turns the motor 2, reverse the current as needed to keep the motor turning in one direction (note the difference between split and slip) But I can't think of a third, sorry.
An AC motor has slip rings and a DC motor has a commutator. With Alternating Current you have the current reversing, and therefore creating an opposite magnetic field, that will continue to push the armature through the other side of the magnetic field. With a DC motor, if you had just slip rings the current, and therefore the magnetic field would not reverse. The motor would do a half turn and stop, because the opposing magnetic fields would attract each other. I don't really know how to explain this with just words. The commutator, in it's simplest form, is two contacts that each cover half of the revolution of the motor shaft. The motor has brushes rubbing the slip rings or commutator, which supply the electric power. When a field is generated the north pole field in the armature attracts to the south pole field in the field coil in the non moving part of the motor's case. The motor would then stop. But, when the motor turns half way the positive and negative electrical contacts touch the opposite side of the commutator, thus reversing the magnetic field in the armature and pushing the motor through another half turn, where the brushes again rub the opposite side and it starts all over again.
DC means direct current, AC means Alternating Current
DC motors use a permanent magnet, making the motor reversible, and the speed adjustable. AC motors use fixed windings, making the direction and speed fixed. The split rings provide a contact surface for the brushes, allow polarity reversal, and a low friction non corrosive wear surface.
The commutator is made of segments. This is what causes the magnetic field to change polarity as the armature turns and so maintains an opposite force between the armature and field. A universal motor has a commutator and can be used on ac or dc. Some dc motors are permanent magnet motors and cannot be used on ac. Another family of motors is induction motors. These can only be used on ac and don't have the commutator, in fact there is no electrical connection (usually) between the rotor (rotating armature) and the stator (static field). The ac terms were derived from dc since motors were first made only for dc.
