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Hi Dink,Why do some motors have a small and others large wire for winding size(dia), and a high or low number of comutator segments? Second what does the number of winding segments mean? High v/s low.

The basic parameter (for the armature) is the number of series turns per pole which then determines the voltage speed relationship for a given magnetic flux per pole. One must also know the armature winding pattern to know the number of parallel circuits.

For a given flux and speed, the more turns, the higher the generated voltage. For a motor running on a fixed voltage, this means the more turns, the slower it turns. But also, the more turns, the higher the torque for a given current.

There is a finite space in the armature for the wire (turns), so when you increase the number of turns, you have to make the wire smaller. And the smaller the wire and the higher the turns, the higher the resistance, and lower the current capability.

So, few turns, large wire, high speed, high current. Many turns, small wire, low speed, low current.

The number of commutator segments (or bars) is chosen by the designer with various considerations, voltage being a primary factor relating to acceptable level of sparking. Often the number of comm bars is set equal to the number of slots in the laminated armature core. How that choice is determined gets into the magnetic structure and manufacturing process and cost benefit analysis which I think is beyond discussion.

Generally speaking, higher voltage motors have higher comm bar counts.

I hope that addressed your questions.

major