Excitation, an electrical term. When an electric current passes through a coil, it generates a magnetic field; this is called an excitation coil. It is also called "magnetization".
What is inrush current? When a power transformer is connected to the grid under no-load conditions or when voltage is restored after an external fault is cleared, a considerable inrush current is generated due to the saturation of the transformer core flux and the nonlinear characteristics of the core material. This inrush current is called inrush current. The value of the inrush current is very large, sometimes reaching 3 to 8 times the rated current, which may cause the transformer differential protection to mistakenly operate as a fault current. Simultaneously, the inrush current can cause winding deformation, thereby reducing the transformer's service life. The multiple harmonic components and DC components contained in the inrush current will degrade the power supply quality of the power system. The high-order harmonics in the inrush current have a strong destructive effect on sensitive power electronic devices connected to the power system.
For generators that frequently lose excitation, two wires (positive and negative) can be drawn from the carbon brush wires of the copper ring. Connect a bell button in series with either wire. Connect 4-8 size D dry cell batteries or storage batteries (dry cell batteries can last for two years without replacement) across the two wires. Ensure the positive and negative terminals are connected correctly. When the generator reaches a certain speed, press the bell button for 1-3 seconds. The generator should then generate electricity normally. If it fails to generate electricity normally, the fault may be: 1. Rectifier burnout; 2. Poor carbon brush contact; 3. Short circuit or open circuit in the excitation lead; or 4. Rotor or stator burnout.
The diesel generator uses self-excitation and should not require a battery. If it's for magnetization, there's no need to start the diesel engine; simply connect the batteries directly to the winding terminals.
When the residual magnetism of the generator core disappears, it should be remagnetized. The remagnetization method is as follows: For self-excited generators, an external storage battery or dry cell battery is typically used. Simply connect the positive and negative terminals of the battery to the excitation winding leads for a short time to provide power. However, it is crucial to correctly identify the polarity of the DC power supply and the excitation winding; connect the positive terminal of the DC power supply to the positive terminal of the excitation winding, and the negative terminal to the negative terminal. If the diesel generator set control panel has a remagnetization circuit, turn the toggle switch to the "magnetize" position to remagnetize the AC exciter. For generators with third harmonic excitation, when the no-load excitation voltage cannot be established, DC power can also be used for remagnetization.
How to force excitation of an engine using an exciter and wiring method
When the generator output voltage drops or a fault occurs, in order to maintain the generator terminal voltage at a certain level and maintain the stability of the power system, the generator exciter is forcibly excited. The effect of forced excitation is to increase the generator terminal voltage.
Forced excitation is achieved by increasing the excitation current and excitation current of the exciter, thereby increasing the excitation amplification factor. Under normal operating conditions, the excitation voltage will not be that high; the excitation current and voltage are only increased when a fault occurs, hence the name forced excitation.
The wiring method for a typical forced-excitation generator depends on its voltage output method. Small generators output voltage from the rotor brushes, while larger ones output voltage from the stator. In fact, its internal wiring method is the same as that of an asynchronous motor.
The 3-phase harmonic excitation winding has 12 poles. The single-phase harmonic winding also has 12 poles, but the connection method is different. The former is connected end to end, while the latter is connected head to head.
The main coil has 4 poles!
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