When you buy series dc motor, you need to understand the reversible operation of the DC motor.
What is a DC motor reversible operation?
A DC motor can in principle be operated both as a motor and as a generator. This principle is called the reversible principle in motor theory.
When the prime mover drives the armature winding to rotate between the main magnetic poles N and S, an electromotive force is induced on the armature winding, and after being rectified into a direct current by the brush and the commutator device, the external load (or the power grid) is led to the external power supply. At this time, the motor operates as a DC generator.
If an external DC power supply is used, the DC current is directed to the armature winding via the brush commutator device, and this current interacts with the magnetic field generated by the main magnetic pole NS to generate torque, which drives the rotor and the mechanical load connected thereto. At this time, the motor is operated as a DC motor.
