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Series Motors

A series wound DC motor has an advantage over the parallel wound motors in that it is a simpler and cheaper controller which can be bought from some vendor. For AC and separately excited DC motors suitable controllers for vehicle use are not on the common market. Technically the best solution is an AC or separately excited DC motor with a proper controller but the cost is much higher. A series wound DC motor produces strong torque at low RPMs which is needed in vehicles. But when the RPM increases the torque goes down very quickly. If the maximum speed is low then a series wound DC motor is a good solution.

A series wound DC motor takes as much current as the controller can deliver in low RPMs, so it doesn’t need less current. When RPM increases it cannot take as much current anymore, and the torque goes down. A separately excited DC motor can take more current at high RPMs and thus produce more torque and power. But the range of an electric vehicle equipped with batteries depends on what the batteries can deliver and the series wound DC motor limits the current and power taken from the batteries at higher speeds by itself, thus producing better range.

Offered by Olli.