JPS6145758Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to low excitation protection for an alternator with the purpose of providing backup protection for the excitation device of the alternator.

A conventional device of this type is shown in FIG. In the figure, 1 is an alternating current generator, 2 is a field winding of the alternator 1, 3 is an excitation transformer that extracts the excitation power of the alternator 1 from the output end of the alternator 1, and 4 is an automatic voltage adjustment. A thyristor rectifier that rectifies the output voltage of the excitation transformer 3 according to the output signal of the transformer 7, 5 is a field switch and a disconnector, 6 is an instrument transformer that takes out the output voltage of the alternator 1, and 7 is an alternating current generator. This is an automatic voltage regulator that works to control the output voltage of machine 1 at a constant level.

Next, the operation will be explained. The excitation power source for the alternator 1 extracts a part of the output of the alternator 1 using an excitation transformer 3, rectifies the output using a thyristor rectifier 4, passes through a field generator and a disconnector 5, It is applied to the field winding 2. On the other hand, AC generator 1
The output voltage is detected by a voltage transformer 6 and fed to an automatic voltage regulator 7. automatic voltage regulator 7
In order to control the output voltage of the alternator 1 to be constant, the deviation between the output voltage of the potential transformer 6 and the reference value is detected and the firing angle of the thyristor rectifier 4 is controlled. It controls the output and the field current of the alternator 1.

Since the conventional excitation device for an alternating current generator is constructed as described above, an abnormality in the automatic voltage regulator causes loss of field, leading to a unit trip. It also had drawbacks such as causing serious damage to the alternator.

This invention has been made in order to eliminate the above-mentioned drawbacks of the conventional excitation device, and aims to provide a highly reliable excitation device by adding an under-excitation protection device for an AC generator that can provide the field current of the low excitation limit of the AC generator as the base for the field current to the conventional excitation device.

An embodiment of this invention will be described below with reference to the drawings.

In Fig. 2, 1 is an alternating current generator, 2 is a field winding of the alternator, 3 is an excitation transformer that takes out the excitation power source of the alternator from the output end of the alternator, and 4
is a thyristor rectifier that rectifies the output voltage of the excitation transformer 3 according to the output signal of the automatic voltage regulator 7, 5 is a field switch and disconnector, and 6 is an instrument transformer that takes out the output voltage of the alternator 1. 7 is AC generator 1
an automatic voltage regulator that provides an output signal to the thyristor rectifier 4 so as to control the output voltage to a constant value;
8 is an induction voltage regulator or a load tap switching transformer that changes the voltage of the excitation power supply according to the output of the alternator 1; 9 is an induction voltage regulator or a load tap switching transformer that rectifies the output voltage of the on-load tap switching transformer 8 and converts it into a field. A rectifier is applied to the magnetic winding 2, 10 is a current transformer that detects the output current of the alternator 1, and 11 is a current transformer that detects the output of the alternator 1 and sends a signal to the induction voltage regulator or on-load tap switching transformer 8. This is a detector that gives

Next, the operation will be explained. The excitation power source for the alternator 1 uses an excitation transformer 3 to take out a part of the output of the alternator 1, rectifies the output using a thyristor rectifier 4, and converts it into a field via a field magnet and disconnector 5. It is applied to the magnetic winding 2. On the other hand, the output voltage of the alternating current generator 1 is detected by an instrument transformer 6 and applied to an automatic voltage regulator 7. The automatic voltage regulator 7 controls the output voltage of the alternator 1 to be constant.
The deviation between the secondary voltage of the instrument transformer 6 and a reference value is detected, the firing angle of the thyristor rectifier 4 is controlled to control the output, and the field current of the alternator 1 is controlled.

Further, the output voltage of the excitation transformer 3 is stepped down by an induction voltage regulator or an on-load tap switching transformer 8, and the voltage is full-wave rectified by a rectifier 9 to provide the output voltage of the rectifier 9 to the field winding. ing. This output voltage is determined by detecting the output of the generator 1 with a detector 11 and using an induction voltage regulator or an on-load tap switching transformer 8 so that the reactive power of the generator as shown by curve A in FIG. 4 is obtained. It's in control.

Next, the voltage waveforms of the main parts of the excitation device according to this invention will be explained with reference to FIG. V ₃ is excitation transformer 3
, V ₈ is the output voltage waveform of the inductive voltage regulator or on-load tap switching transformer 8, V ₄ is the output voltage waveform of the thyristor rectifier 4, V ₉ is the rectified voltage waveform of the rectifier 9, and V ₂ is This is a field voltage waveform that is a composite voltage waveform of V ₄ and V ₉ and is applied to the field winding.
Here, the rectified voltage waveform 4 corresponds to the field voltage that maintains curve A in FIG.

If the excitation device is operating normally under the above conditions, the output voltage of the generator will be maintained at the specified value, and the field voltage will be in the state of V ₂ in FIG. 3. If an abnormality occurs in the automatic voltage regulator 7 and the output of the thyristor rectifier 4 becomes zero, the field current will be transferred to the excitation transformer 3, the induction voltage regulator or the on-load tap switching transformer 8, and the rectifier 9. will be supplied through
The field voltage is V ₉ in Figure 3. In this way, a field current at the low excitation limit of the generator is secured, and operation can be continued without damaging the generator.

Although the above embodiment describes a method in which the excitation power source for the alternator is taken from the output end of the alternator, it may be taken from another power source.

Further, in the above embodiment, a method without an exciter was described, but even with an exciter, the same effects as in the above embodiment can be obtained.

As described above, this invention adds an AC generator low excitation protection device that can provide the low excitation limit field current of the AC generator as the base of the field current to the conventional excitation system, resulting in highly reliable An excitation device is obtained, and the excitation device and low excitation protection device are supplied with a part of the output of the alternator, and are not supplied with power from an external power generation device, etc., so the entire device is simplified, and, The underexcitation protection device is controlled by a detector that detects the output of the alternator, so that the reactive power of the alternator is obtained.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing a conventional excitation device for an alternator, Fig. 2 is a system diagram showing an embodiment of an excitation device for an alternator according to the present invention, and Fig. 3 is for explaining the present invention. FIG. 4 is an explanatory diagram showing the possible output range of the generator. In the figure, 1 is an alternator, 2 is a field winding,
3 is an excitation transformer, 4 is a thyristor rectifier, 7
is an automatic voltage regulator, 8 is an inductive voltage regulator or on-load tap switching transformer, 9 is a rectifier, and 11 is a detector.

Claims (1)

[Scope of utility model registration request] An excitation transformer that derives the output of the alternator according to the excitation current, a thyristor rectifier that rectifies and outputs the output of the excitation transformer, and an induced voltage regulator that steps down the output of the excitation transformer. an automatic voltage regulator that compares the output voltage of the alternator with a set value and controls the firing of the thyristor rectifier according to the deviation;
a detector that detects the output current of the alternator and provides a signal to the induction voltage regulator or on-load tap-changing transformer; a rectifier that rectifies the output of the induction voltage regulator or on-load tap-changing transformer; and the rectifier. and a field winding inputting the combined output from the thyristor rectifier, and when the output from the thyristor rectifier becomes zero, the low excitation limit from the induced voltage regulator or on-load tap switching transformer is removed. An excitation device for an alternator, characterized in that a field current is output to the field winding.