In the diesel generator set, the normal double pulse trigger circuit cannot be used for residual voltage excitation. First, check the conduction mechanism of the thyristor. Think of the thyristor as the interconnection of two transistors, as shown in, and inject trigger current into the gate.
When the external load is enough, Ig will form a strong positive feedback to make the two tubes saturated and conductive. The process of positive feedback is: the current amplification coefficient of one Ia, one Icl, one Ig thyristor varies with the emitter current, that is, when the emitter current is small, the current amplification coefficient is small, and vice versa.
However, the emitter current of diesel generator set is also subject to external voltage and the working principle diagram of the external load thyristor. The condition for the thyristor to turn off is to make the thyristor current lower than that of the thyristor rectifier bridge used to maintain electricity to supply power to the generator rotor.
We only care about the dynamic process of rotor current at the moment of thyristor conduction of diesel generator set. The following differential equation can be used to describe that Vt is the voltage drop of tube, brush contact and other voltage drops. U2 is a sine function. For simplicity, it can be replaced by the instantaneous value of the initial conduction voltage within 60 degrees. U2 is the effective value of the secondary side line voltage of the excitation transformer. As a result, the unit frequency can be set as 50Hz.
It can be seen from this that, in a sinusoidal period, due to the narrow pulse width of the dual pulse, if the single pulse trigger of the diesel generator set thyristor is not enough to make the current flowing through the thyristor conduct in the forward direction, the residual voltage excitation of the dual pulse fails.
Analysis on excitation mechanism of diesel generator set with high-frequency pulse residual voltage From the conduction mechanism of thyristor, it is known that the conduction of thyristor is formed by triggering current, and the thyristor is conducted when the conduction current of thyristor reaches the maintenance current. It is triggered by wide pulse or high frequency pulse with enough high frequency. When the forward voltage of the thyristor exists and is high enough, the thyristor can flow through the crystal and the current of the thyristor can reach the maintenance current and be turned on.
Main circuits and principles of several power converters commonly used in diesel generator sets. Preface: The winding of SRM switched reluctance motor only needs unidirectional current, but it should be able to quickly receive electric energy from the power supply and feed back energy to the power supply. Since SRM power converter only needs to provide unidirectional current to the motor, it is simpler and more reliable than asynchronous motor PWM converter.
However, the working current and voltage waveform of SRM of diesel generator set is not sine wave, and the waveform is restricted by the operating conditions of the system and the design parameters of the motor, so it is difficult to accurately predict. This makes the quota calculation of its main switching devices more complicated.
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