Electromagnetic DC motor is composed of stator poles, rotor (armature), commutator (commonly known as commutator), brushes, casing, bearings, etc.
The stator pole (main pole) of an electromagnetic DC motor is composed of an iron core and an excitation winding. According to the different ways of excitation (the old standard is called excitation), it can be divided into series excitation DC motor, parallel excitation DC motor, other excitation DC motor and compound excitation DC motor. Due to the different excitation methods, the laws of the stator pole magnetic flux (generated after the stator pole excitation coil is energized) are also different.
The field winding and the rotor winding of the series-excited DC motor are connected in series through the brush and the commutator. The excitation current is proportional to the armature current. The magnetic flux of the stator increases with the increase of the excitation current, and the torque is approximately The square of the armature current is proportional to the speed, and the speed drops rapidly with the increase of torque or current. The starting torque can be more than 5 times the rated torque, and the short-term overload torque can be more than 4 times the rated torque. ). Speed ​​regulation can be achieved by using external resistors in series (or parallel) with the series winding, or by connecting the series winding in parallel.
The excitation winding of the parallel-excited DC motor is connected in parallel with the rotor winding, the excitation current is relatively constant, the starting torque is proportional to the armature current, the starting current is about 2.5 times the rated current. The speed decreases slightly with the increase of current and torque. The short-term overload torque is 1.5 times the rated torque. The speed change rate is relatively small, 5% ~ 15%. The speed can be adjusted by the constant power that weakens the magnetic field.