Abstract : This paper analyzes commonly used excitation protection methods for DC motors and proposes effective improvement measures for excitation protection. These measures have yielded good results in practical applications. Keywords : DC motor, excitation protection. Before starting and during operation, DC motors must ensure that their excitation windings are supplied with DC excitation current in the correct direction. If there is no excitation current in the excitation winding, the motor will have only a small residual magnetism. Under the influence of the motor armature power supply, the motor speed will rise very high, resulting in a "runaway" accident. This situation can cause damage to mechanical equipment and personal injury. If a reverse excitation current is supplied to the excitation winding, the motor speed will reverse. For production machinery that cannot be reversed, this will inevitably cause mechanical damage and affect personal safety. Therefore, we must attach great importance to the excitation protection of DC motors. This paper analyzes commonly used excitation protection methods and proposes effective improvement measures for excitation protection. 1. Loss of Excitation Protection Methods Currently, commonly used loss of excitation protection methods can be roughly divided into two types according to the capacity of the drive system. (1) Small-capacity DC drive system. This type of system uses a small-capacity DC motor, typically with a power not exceeding 5.5kW, and its excitation current is also small, generally not exceeding 2A. A common protection method is to insert an undervoltage relay coil (kV) into the excitation circuit, with a high-power, low-resistance rheostat R connected in parallel across its terminals, as shown in Figure 1. In the figure, k is the excitation winding of the DC motor, u is the DC excitation voltage, and J is the DC excitation current. [b][align=center]For more details, please click: Excitation Protection of DC Motors[/align][/b]