Cha Myong Song, a researcher at the Faculty of Electrical Engineering, has completed the principle and method for stabilizing voltage from no-load state to normal load state.
Although existing 3 harmonics exciting synchronous generators realized the stabilization of voltage by changing the structure of pole shoes, they failed to provide a reasonable value range of 3 harmonics flux density.
According to the new method, 3 harmonics flux density and the output power of 3 harmonics winding and exciting winding are decided and the windings are connected to exciting regulation resistors in order to improve the efficiency of the generator and decrease voltage changing rate. The 3 harmonics exciting synchronous generator, which consists of 1 harmonics winding, 3 harmonics winding, full-wave recification circuit, exciting winding, exciting regulation resistor, guarantees enough self exciting and decreases voltage changing rate by regulating the parameters of 3 harmonics winding, exciting winding, pole structure and exciting regulation resistors.
If 3 harmonics flux density is much higher than 1 harmonics flux density, voltage waveform gets non-sinusoidal, and if much lower, self exciting may not occur. Therefore, 3 harmonics flux density should be defined within the range of 4~6% of 1 harmonics flux density by the field analysis method.
The parameters of 3 harmonics winding and exciting winding should be defined to be reasonable by the equivalent circuit method.
The efficiency of the generator and the exciting stability depend on the designs of 3 harmonics winding and exciting winding.
The 3 harmonics exciting synchronous generator is low in manufacturing cost and ensures enough self exciting in it. Its voltage changing rate decreases to 1.4% and its efficiency improves to 90.9%.
This method of voltage stabilization is also applicable to small independent gas generators.
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