JPS586377B2 - AC synchronous machine field current measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is mainly suitable for a field current measuring device for a brushless synchronous machine.

An example of a conventionally known method for measuring the field current of this type of rotating machine is shown in FIG.

In the figure, 1 is the stator of the synchronous generator, 2 is its rotating part, 2a is the rotating armature winding of the AC exciter, and 2b is the rotation for rectifying the output of the armature winding 2a of the AC exciter. rectifier, 2C is the field winding of the synchronous generator, 3 is the field winding of the AC exciter, 4 is the shunt inserted in the field winding circuit of the AC exciter, 5 is the field current of the AC exciter It is a total.

Next, this device will be explained.

The field winding 2c of the synchronous generator, together with the rotating rectifier 2b and the armature winding 2a of the AC exciter, is constantly rotating during operation, and the field current cannot be directly measured.

Therefore, instead of measuring the synchronous generator field current, the field current of the AC exciter is measured using the field ammeter 5 of the AC exciter, which has an almost relative relationship, and the field current of the synchronous generator is estimated. There is.

In order to estimate the field current of a conventional synchronous generator using this method, errors due to saturation of the magnetic circuit of the AC exciter, field winding 2C of the synchronous generator, and armature winding 2a of the AC exciter are
The problem is that the error due to temperature changes is large, and in practical terms it is only useful as a guide.

Furthermore, it is not possible to directly read the field current of the synchronous generator,
Another drawback is that it takes time and effort to estimate the current value.

This invention was made with the aim of eliminating the drawbacks of the conventional devices as described above. By detecting the internal induced voltage of the synchronous machine, the field current of the synchronous machine, which is proportional to the internal induced voltage, can be detected. The object of the present invention is to provide a field current measuring device suitable for detecting the field current of a brushless synchronous machine with high precision and capable of directly reading the field current.

Next, one embodiment of the present invention will be described based on the drawings.

In Fig. 2, 7 is a current transformer for detecting the output current of the alternator 1, and 8 is a function converter energized by the terminal voltage of the synchronous generator, which flows into the field winding of the generator. The so-called 4th generation of the field current and the generator voltage generated in the generator 1
It has an input/output relationship as shown in FIG. 5, which is similar to the no-load saturation characteristic curve shown in the figure.

9 is a voltage detection circuit that generates a voltage proportional to the internal induced voltage of the synchronous generator 1, and 10 is a conversion display device that converts the internal induced voltage of this voltage detection circuit as a field current and displays it.

Note that the other configurations are the same as the conventional device shown in FIG. 1, so the explanation will be omitted.

As described above, this invention detects the internal induced voltage generated in the alternator 1 and displays it as a field current.The relationship between the field current and the internal induced voltage is determined by the temperature of the field winding. This takes advantage of the fact that there is always a constant relative relationship regardless of the low resistance change due to change.

FIG. 3 is an embodiment of the voltage detection circuit 9, and FIGS. 6 and 7 are vector diagrams for explaining the device shown in FIG. 3.

In FIG. 3, 7 is a current transformer for detecting the output current of the alternator 1, and 8 is a function for detecting the terminal voltage of the alternator 1 and correcting the magnetic saturation characteristics of the alternator 1. Converter 11 is a transformer for vector synthesis of the output voltage of the function converter 8 and a voltage proportional to the output current of the alternator 1 detected by the current transformer 7; 12 is a secondary of the current transformer 7; A low resistor that shunts the current, E1 is the secondary voltage of the transformer 11, E
2 is the voltage across the resistor 120, and E3 is the output voltage of the voltage detection circuit 9, which is proportional to the field winding current of the alternator.

In FIG. 6, Eu, Ev, and Ew are the phase voltages of the alternator 1, Iv is the V-phase current, and θ is the power factor angle.

In FIG. 7, Et and ■ are the terminal voltage and output current of the alternator 1, ■·xd is the voltage drop due to the synchronous impedance xd of the alternator 1, and Eo is the internal induced voltage of the alternator 1.

In FIG. 3, when the function converter is connected between the U and W phases and the current transformer 7 is connected to the V phase, the vectors of El and E2tE3 become as shown in FIG. 6.

That is, E1 has the same phase as Ewu based on the composite vector Ewu of Eu and Ew, and E2 has the same phase as Iv based on the V-phase current Iv.

Here, E1 is a value proportional to Et, and E2 is a value proportional to ■, so the function converter 8, resistor 12, and transformer 11
If , is selected appropriately, the triangle formed by E, , E2, and E3 in Figure 6 and the triangle formed by Et, I xd, and Eo shown in Figure 7 can be obtained regardless of the load size or power factor. They become similar shapes.

Therefore, the voltage E3 is the internal induced voltage E of the alternator 1.
o, and maintains a constant proportional relationship with the field current.

In this embodiment, an AC synchronous generator has been described, but the field current can be similarly detected and measured for an AC synchronous motor.

As described above, according to the present invention, the field current of the AC synchronous machine can be detected by detecting the internal induced voltage of the AC synchronous machine, so the field current of the brushless synchronous machine can be directly read. It is possible to detect field current with less error due to resistance change in the field winding and less error due to magnetic saturation.

Furthermore, the rotating part may have the same structure as before, and a highly accurate field current detection and measurement device that can be easily installed even after the AC synchronous machine is manufactured can be obtained.

[Brief explanation of drawings]

Fig. 1 is a wiring diagram of a brushless synchronous machine to explain a conventional device for estimating field current of a synchronous machine, and Fig. 2 is a wiring diagram showing a field current detection and measurement device according to an embodiment of the present invention. , Fig. 3 is a wiring diagram showing an embodiment of the voltage detection circuit for explaining the device shown in Fig. 2, Fig. 4 is a no-load saturation characteristic curve of an AC synchronous machine, and Fig. 5 is the present invention. Characteristic curves showing the input and output relationships of the function converter, FIGS. 6 and 7 are vector diagrams for explaining the voltage detection circuit shown in FIG. 3. In the figure, 1 is the AC generator, 2 is the rotating part, 3 is the field winding of the AC exciter, 4 is the shunt, 5 is the AC exciter field ammeter, 7
8 is a current transformer, 8 is a function converter, 9 is a voltage detection circuit, 10 is a field current display device, 11 is a transformer, and 12 is a resistor. In each figure, the same symbols indicate the same or equivalent parts.

Claims (1)

[Claims] 1 It is energized by the voltage between the first and third phase terminals on the AC side of a three-phase AC synchronous machine, and has an input/output relationship similar to the no-load saturation characteristic curve of the field current and internal induced voltage of the above synchronous machine. a current transformer and a voltage transformer for obtaining an output voltage proportional to the phase current of the second phase of the synchronous machine; an output voltage of the function converter and an output of the current transformer and the voltage transformer; 1. A field current measuring device for an AC synchronous machine, comprising a device that responds to a composite voltage.