The four excitation methods for DC motors include:
Constant magnet excitation: also known as permanent magnet excitation. In this way, the motor uses a constant permanent magnet as the magnetic pole, without the need for external power supply, thus the motor has high efficiency and stability. However, in this way, the motor cannot achieve speed regulation function.
Series excitation: In this method, the armature and excitation coil are connected in series, and the armature and excitation coil share a common power source. In this way, the motor has a high starting torque and a wide speed adjustment range, but its efficiency is low and it is prone to excitation loss of control.
Parallel excitation: In this method, the armature and excitation coil are connected in parallel, and the armature and excitation coil are powered by different power sources. In this way, the motor has high efficiency and stable operating characteristics, but the speed adjustment range is narrow.
Composite excitation: In this method, the motor adopts both series and parallel excitation methods, that is, the armature and excitation coil use both series and parallel excitation methods simultaneously. In this way, the motor has the advantages of large starting torque, wide speed adjustment range, and high efficiency, but the manufacturing and maintenance costs are high.
The above are four excitation methods for DC motors, each with its own scope of application and advantages and disadvantages. The appropriate method should be selected based on specific needs and application scenarios.