Jul. 30, 2021
Volvo diesel generator sets rarely have short circuits problem during use. What are the main reasons and how to solve? 100KW generator manufacturer shares with you.
1. The characteristics of sudden short circuit.
In the case of a steady-state short-circuit, due to the large synchronous reactance, the steady-state short-circuit current is not large, and in the case of a sudden short-circuit, because the super-transient reactance limiting the current is small and contains a direct current component, the sudden short-circuit current is large , Its peak value can reach more than ten times the rated current.
With the emergence of this inrush current, the windings of the motor will be subjected to a large impact electromagnetic force, which may deform the windings and even damage the insulation of the windings.
In the process of a sudden short circuit, the motor is subjected to a strong short-circuit torque, and vibration may occur.
The stator and rotor windings of the motor have overvoltage.
2. The characteristics of the physical phenomena inside the generator during a sudden short circuit.
In the case of a steady-state short-circuit, the armature current is constant, and the corresponding armature magnetomotive force is a constant amplitude rotating magnetic field rotating at a synchronous speed, so it will not induce electromotive force in the rotor windings and generate current. From the current relationship Look, it is equivalent to the open state of the transformer.
When a sudden short circuit occurs, the magnitude of the armature current changes, and the corresponding armature magnetic field amplitude changes. Therefore, the transformer acts between the stator and the rotor, which induces electric potential and current in the rotor windings, and then affects the stator windings. From the perspective of electromagnetic relationship, the change of the medium current is equivalent to the sudden short-circuit state of the transformer.
During the normal power generation process of Volvo diesel generator set, the electrical equipment suddenly short-circuited and a large fireball appeared, which caused the generator voltage and frequency to disappear, and the diesel engine was started to the rated speed again, and the generator could not establish voltage.
After the operator or maintenance person finds such a fault, they should check the excitation fuse first, and then check the generator's stator, exciter and generator control parts. Only after confirming that there are no damaged parts can the diesel engine be started. If the generator is not generating electricity, the residual magnetization voltage of the exciter should be checked.
Cause of faults:
(1) There is an open circuit or short circuit inside the exciter.
(2) The excitation fuse is open.
(3) Second tube breakdown.
(4) There is a short circuit or open circuit inside the reactor.
(5) The residual magnetism of the exciter disappears.
The control part of this diesel generator set adopts phase compound excitation automatic voltage regulation, so when troubleshooting this kind of fault, it is necessary to understand the principle of phase compound excitation automatic voltage regulation and component composition and the role of each sub-system, and then follow the steps from simple to The principle of complicated inspection.
(1) Check the fuse and find that the fuse has been blown. Observe whether the parts in the control box are scorched. During the inspection, it is found that the limited-current two tubes are burned out.
(2) Use a multimeter to measure the 6 rectifier diodes, and no abnormality was found from the test results.
(3) Use a multimeter to test the resistance of the exciter, and the measured resistance is 3.5Ω, which shows that the internal winding of the exciter is damaged (the normal resistance is about 0.5Ω).
(4) After replacing the second current limiting tube and the fuse, when the diesel engine is started to the rated speed, the generator will not generate electricity.
This shows that the fault may be that the internal remanence voltage of the exciter is too low (in the process of normal power generation, the electrical equipment suddenly short-circuits and a large fireball appears, which will cause the internal remanence voltage of the exciter to disappear.
(5) After magnetizing the exciter with the battery, start the diesel engine to the rated speed, and the generator will start to generate electricity and meet the specified requirements.
If you are interested in Volvo diesel generators, contact Dingbo Power company by email firstname.lastname@example.org.
May. 14, 2022
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