Three-phase generators are a type of generator commonly used in large workshops and factories. After prolonged use, the residual magnetism in the generator will disappear, causing the generator to lose magnetization and be unable to build voltage, thus failing to produce electricity. For smaller generators, a temporary high-power load can be added to build voltage, which is to create a closed circuit between the generator coil and the load, using the generator's remaining weak residual magnetism to build voltage. 1. First, start the turbine (or diesel engine) to a certain speed, use a 12V battery to magnetize and build voltage in the generator. This method can only be done by touching, as the excitation voltage of the generator after building voltage can reach 40~90V, and if the battery is not quickly disconnected, it will damage the battery. 2. Use a generator magnetizer to magnetize the generator rotor, which can be done while the generator is static. The hazards of generator demagnetization to the power system: 1. When a generator loses magnetization, it will absorb reactive power from the system, causing the voltage in the power system to drop. 2. If the power system capacity is small or the reactive power reserve is insufficient, the voltage at the generator terminal, the high-voltage side of the step-up transformer, or other nearby points may fall below the allowable value, thus disrupting the stable operation between load and power source, and even causing a voltage collapse in the power system. 3. When a generator experiences low excitation or demagnetization, the voltage drop will cause other generators in the system to increase their reactive power output under the automatic adjustment of the excitation device, leading to certain electrical components in the system. 4. When a generator experiences low excitation or demagnetization, due to the fluctuation of active power and the drop in system voltage, it may cause the adjacent generators operating normally to lose synchronization with the system or between different parts of the power system, causing system oscillation and large-scale shedding of load.