A generator is a mechanical device that converts other forms of energy into electrical energy. It is driven by a water turbine, a steam turbine, a diesel engine, or other power machinery to convert energy generated by water flow, gas flow, fuel combustion, or nuclear fission into mechanical energy that is transmitted to the generator. It is then converted to electrical energy by a generator.
Generators have a wide range of uses in industrial and agricultural production, national defense, technology and daily life. There are many forms of generators, but their working principles are based on the laws of electromagnetic induction and the law of electromagnetic force. Therefore, the general principle of its construction is to form magnetic circuits and circuits that are electromagnetically induced with each other with appropriate magnetic conductive and conductive materials to generate electromagnetic power for energy conversion purposes.
Diesel generatorsThe diesel engine drives the generator to operate, converting the energy of the diesel into electrical energy.
generator
In the cylinder of the diesel engine, the clean air filtered by the air filter is fully mixed with the high-pressure atomized diesel fuel injected from the injector. Under the upward extrusion of the piston, the volume is reduced and the temperature is rapidly increased to reach the ignition point of the diesel. The diesel is ignited, the mixed gas burns violently, and the volume expands rapidly, pushing the piston down, called 'work'.
Gasoline Generator
The gasoline engine drives the generator to operate, converting the energy of the gasoline into electrical energy.
In the cylinder of the gasoline engine, the mixed gas burns violently, and the volume expands rapidly, pushing the piston to work downward.
Whether it is a diesel generator or a gasoline generator, each cylinder performs work in a certain order, and the thrust acting on the piston becomes a force that pushes the crankshaft to rotate through the connecting rod, thereby driving the crankshaft to rotate. By installing the brushless synchronous alternator coaxially with the crankshaft of the power machine, the rotor of the generator can be driven by the rotation of the power machine. By using the principle of 'electromagnetic induction', the generator will output an induced electromotive force, and a current can be generated through the closed load circuit. .
Principle of generator under-excitation limit and under-excitation protectionWhat is the under-excitation limit?
Answer: During the under-excited operation of the generator, the magnetic field connection between the stator and the rotor is weakened, and the generator is easy to lose static stability. In order to ensure a certain static stability margin, the excitation control system (AVR) is designed with an under-excitation limit circuit, that is, when the generator outputs a certain amount of active power, it is limited by the heating of the stator core, and the power angle cannot be To overcome the limitation of the stability limit, in order to ensure the safety of the generator equipment, it is necessary to ensure that the generator operates within the power limit circle and the thermal stability limit line. The specific settings are based on the test and the phase-input capacity limit data provided by the unit, and must be combined with the power generation. Machine loss of magnetic protection.
What is under-excitation protection?
Answer: The excitation regulator under-excitation protection switches the regulator to the standby channel to maintain operation when the under-excitation limit is disabled. This alternate channel can be another automatic channel or a manual channel. The stability of the manual mode operation is lower than that of the automatic mode. To ensure that the under-excitation protection switches to the manual mode stable operation, the manual mode minimum excitation limit is set, and its value is related to the generator operating point.
What are the principles of under-excitation and under-excitation protection?
Answer: The under-excitation limit and protection function of Cummins generator set must match the generator loss-of-magnetism protection. Any operation or power system disturbance should ensure that the under-excitation limit is prior to the under-excitation protection action, and the under-excitation protection is de-energized before the generator. Protection actions, there must be a certain margin between them.
What is the strong incentive limit?
Answer: In order to prevent the rotor winding from overheating and being damaged, when the current of the Cummins generator exceeds a certain value, the limit acts, and the excitation signal of the excitation is reduced by the AVR integrated amplification circuit output.
What is the performance of generator overexcitation?
Answer: The overexcitation of the generator is reflected as the change of each electrical parameter, which is mainly manifested by high excitation current, no power power overload and stator overcurrent.
What are the maximum excitation limits for generators?
Answer: Cummins diesel generators have two maximum excitation limits: the no-load maximum excitation current limit to prevent generator overvoltage and the maximum excitation current limit to prevent overcurrent on the excitation winding side.
What is the role of the maximum excitation current limit of the load?
Answer: The maximum excitation current limit of the load is to prevent the strong excitation current from occurring on the rotor side of the generator. During the operation of the generator, when the DC side of the excitation power cabinet fails or the field winding is short-circuited, the excitation current of the generator rises rapidly. If the current is not effectively suppressed, the fault point will be further expanded, and the development of an arc short circuit will cause greater damage to the generator, and the fault current will also damage the equipment of the excitation system.
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