The excitation mode of the DC motor refers to the problem of how to supply the excitation winding and to generate the magnetic flux potential and to establish the main magnetic field. According to the different excitation modes, the DC motor can be divided into the following types:
1 He DC motor
There is no connection between the excitation winding and the armature winding, and the DC motor, which is supplied by other DC power supply to the excitation winding, is called the excitation DC motor.
2. Shunt DC motor
The excitation winding of the shunt excitation DC motor is parallel to the armature winding. As a shunt generator, the terminal voltage generated by the motor itself is supplied by the excitation winding. As a shunt motor, the excitation winding and armature share the same power, and the performance is the same as that of the DC excited DC motor.
3. series excited DC motor
The excitation winding of the series excited DC motor is connected in series with the armature winding, then it is connected to the DC power supply. The excitation current of this kind of DC motor is the armature current.
4. complex excitation DC motor
The complex excitation DC motor has two excitation windings with shunt excitation and series excitation. If the flux potential generated by a series of excited windings is the same as the direction of the flux potential generated by the shunt winding, it is called the complex excitation. If the two direction of magnetic flux is opposite, it is called the differential complex excitation.
The DC motor with different excitation modes has different characteristics. Generally speaking, the main excitation modes of DC motor are shunt excitation, series excitation and compound excitation. The main excitation modes of DC generator are excitation, shunt and compound excitation.
(1) the performance of speed regulation is good. The so-called "speed performance" refers to the changes in the speed of the motor artificially under the condition of a certain load. The DC motor can realize uniform and smooth stepless speed regulation under heavy load, and the speed range is wide.
(two) the starting moment is large. The speed regulation can be realized evenly and economically. Therefore, all machines that start or require uniform speed regulation under heavy loads, such as large reversible rolling mills, hoists, electric locomotives, trams, etc., are all driven by DC motors.