The commutator

[NE2000]

Can someone please basically explain exactly how the commutator does what it does? Like why does the current reverse every half-cycle, what is it about the commutator that makes that happen? Thanks heaps.

Also what effect does the commutator have when you are running from an AC supply (using a permanent field, i.e. the motor won't rotate as the current changes direction at 50 Hz).

[TrueTears]

The commutator is normally used in a DC motor. It has 2 split rings attached to it.

As the motor turns (let's say clockwise) and say it begins "flat" against the magnetic field (ie lying 180 deg to it), as it turns to its 90 deg position (directly perpendicular to the mag field) the split rings on the commutator will rotate with the motor, so as the motor rotates to the 90 deg position the 2 split rings change position and touch the opposite terminals. This way the current is "manipulated" to be reversed. It is still DC current as the terminals themselves don't change, it is just the position of the split rings that do.

For AC motor, if you use commutators it will oscillate for a bit when it gets to its 90 deg position and stop.

[NE2000]

The commutator is normally used in a DC motor. It has 2 split rings attached to it.

As the motor turns (let's say clockwise) and say it begins "flat" against the magnetic field (ie lying 180 deg to it), as it turns to its 90 deg position (directly perpendicular to the mag field) the split rings on the commutator will rotate with the motor, so as the motor rotates to the 90 deg position the 2 split rings change position and touch the opposite terminals. This way the current is "manipulated" to be reversed. It is still DC current as the terminals themselves don't change, it is just the position of the split rings that do.

For AC motor, if you use commutators it will oscillate for a bit when it gets to its 90 deg position and stop.

Thanks!

[BlueYoHo]

But how does the current get "manipulated"? I understand why it needs to be reversed and everything else, but I don't get how it gets reversed...

Say you were making one, and you have the split ring things that are supposed to be brushed on something... what is that something and what do you need to do to it so that it can change the direction of the current?

[NE2000]

But how does the current get "manipulated"? I understand why it needs to be reversed and everything else, but I don't get how it gets reversed...

Say you were making one, and you have the split ring things that are supposed to be brushed on something... what is that something and what do you need to do to it so that it can change the direction of the current?

The commutar has two metal parts (split rings) that are separated by an insulating space. You've probably seen this on a diagram.

The brushes are essentially the positive and negative terminals from the DC source.

As the motor coil rotates, the commutator will rotate too (with the coil). Throughout one half rotation, say Split Ring A will be touching the positive terminal and Split Ring B will be touching the negative terminal. When it crosses that vertical point, the rotation of the commutator means Split Ring A is touching the negative terminal and Split Ring B is touching the positive terminal. The result is a reversal of current.

[BlueYoHo]

Ahhhh ok i get ya, thanks

[naved_s9994]

can anyone show this info, through any possible diagram image?

[TrueTears]

can anyone show this info, through any possible diagram image?

Check Jarcaranda if you're using it. Good diagram there.

[naved_s9994]

na
screenshot? or something?

[TrueTears]

That is one hell of a concise diagram and explanation.

[naved_s9994]

ahaha, THANKS sooooo much TT

your soo helpful