Commutation in DC Motors vs BLDC: How Is Current Reversal Achieved Without a Commutator?

Hi all, I am new to this forum. Can anyone explain me clearly what is commutation? I referred in web and knew something that commutator reverses the directions of the current flow. In both DC and BLDC it is possible to achieve the clockwise and anticlockwise by changing the polarity then what exactly a commutator does? why it need to reverse the current flow direction. How it could be achieved in BLDC without commutator? I am confused alot, Someone gives clear idea will be helpful Thanks Pon

Motors that work directly on AC do not have commutators. Commutation refers to converting DC into AC inside the motor, and is done, in a DC motor via commutators.

In a typical brushed DC motor, at the very least there is one winding on the rotor (collectivelty called "armature") that are connected to the commutators at one end. A pair of brushes contacts the commutators. When DC is applied, a magnetic field build up and the armature spins in a direction as per the polarity. As soon as the armature has moved by 180 degrees, the commutation causes the applied voltage also to reverse - this again causes the armature to keep rotating in the same direction. So the winding moves 180 degrees and then has a polarity "correction" which is the same as applying +ve and -ve pulses alternatively - an AC voltage.

In a brushless DC motor, the commutation is done electronically via transistor or FET switches - arranged in a half or full bridge configuration which simply alternatively applies pulses to the coil. In these motors the winding remains stationary but the magnet is caused to spin.

Hi rohit,

Thanks for your kind replay, Can I say all brushed DC motors have stationary magnet and rotating coil and it is vice versa for DC brushless motor and also for stepper.??

Is that commutator is the stationary part contact occasionally contact with moving armature or commutator itself will moving part??

Can you send me any web link for animation or tutorials for motors.

I have another doubt that linear motor has permanent stationary magnetic track besides to moving coil, how it could be referred as BLDC motor??

If it possible could you give short and clear note on linear motor too!!

Thanks

Pon

Refer to these:

"https://en.wikipedia.org/wiki/DC_motor(https://en.wikipedia.org/wiki/DC_motor)":https://en.wikipedia.org/wiki/DC_motor

"https://en.wikipedia.org/wiki/Brushless_DC_electric_motor(https://en.wikipedia.org/wiki/Brushless_DC_electric_motor)":https://en.wikipedia.org/wiki/Brushless_DC_electric_motor