JPS6117208B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a brushless rotating electric machine, and in particular, the armature output of an AC exciter is rectified by a rotary rectifier and added to the main machine field, and ground faults in the field circuit of the excited brushless rotating electric machine are detected in a non-contact manner. related to a device for Generally, as a field circuit ground fault detection device for an AC machine that excites the main machine field with DC current through a brush, one end is grounded through a detection brush and a DC power supply to the AC machine field circuit, and the ground fault current is Structures that are equipped with ground fault detection devices such as relays that are operated by In the brushless method, it is difficult to detect it as easily as in the case with a brush, and detection and power supply are done through a slip ring, which creates a non-contact structure rather than a completely non-contact structure. In this case, a rotary transformer is used, but this rotary transformer creates a rotor side coil concentric with the shaft,
It must be installed on the rotor, transmit and receive power between the windings on the fixed side, and receive the ground fault signal using another rotary transformer, making the structure complex and expensive. There is. An object of the present invention is to provide a non-contact detection device that is completely non-contact, has a simple and inexpensive structure, and can detect ground faults in a field circuit with high reliability. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of the invention, in which a rotor 2 rotating opposite to a stator 1 of an alternating current generator, which is a synchronous machine, is connected to an alternating current exciter armature winding 3.
After converting the output of It is configured with a brushless excitation system.
Separately from the field circuits 6 and 7, the output of the AC exciter auxiliary winding 8 is connected to the AC input terminals 10 and 11 of the rectifier circuit 9, and the negative side terminal 12 on the DC output side is connected to the rotor 2. It is connected to the point E of the rotor body and grounded, and the positive side terminal 13 is connected to the negative side field circuit 7 of the rotary rectifier 4 via the detection winding 14 and the current limiting resistor 15. The auxiliary winding 8 is wound in the same slot (not shown) as the armature winding 3, and electric power is supplied brushless by DC exciting the AC exciter field winding 16. . Next, the detection winding 14 constitutes an electromagnet, and is arranged to be magnetically coupled to a detection device 18 consisting of a winding (which may be a Hall element) provided on the fixed side. The detection device 18 includes the detection winding 1
4 constitutes an electromagnet and rotates, so a corresponding speed electromotive force is generated, and its output is sent via a comparison circuit 19 and a detection circuit 20 to a display, alarm, etc.
It is connected to an alarm device 21 such as a relay. The comparison circuit 19 compares a signal proportional to the field current with the output of the detection device 18 via a current detection device 22 using a shunt in the AC exciter field winding 16 circuit, etc.
A signal output commensurate with the magnitude of the ground fault current is sent to the detection circuit 20. In this embodiment, the comparison circuit 19, the detection circuit 20, the alarm device 2
The structure and function of the first class are not intended.
These are blackboxed because they depend on the operation and control system of the plant where the main engine is installed. In reality, this can be done by computer control using digital processing, and the detection device 18 and current detection device 22 are regarded as sensors, and their respective analog outputs are A/D converted, and the main computer or dedicated microcomputer etc. It is possible to use a method of division. Next, the effect will be explained. Now, the operation in a state where the rotor main body is grounded at point A in the positive field circuit 6 in FIG. 1 will be described. Auxiliary winding 8
The AC voltage induced in the rectifier circuit 9 converts the AC voltage into DC voltage to create a rectifier voltage V _D. The rectifier voltage V _D enters in series in the direction of the sum (V _D +V _f ) with the field voltage V _f , and connects point A - point E - rectifier circuit 9 - detection winding 14 - current limiting resistor 15 - generator. A ground fault current is passed through the circuit connecting the field windings 5, the detection winding 14 is excited with direct current, and a magnetic field linked to the detection device 18 is created. Since the detection winding 14 is rotating together with the rotor 2, a velocity electromotive force is induced in the detection device 18 by the moving magnetic field, which is input to the comparison circuit 19. The comparison circuit 19 compares the main machine field voltage (which is proportional to the field current of the AC exciter) and the input signal. This is the value of the ground fault current necessary to DC excite the detection winding 14, induce a speed electromotive force in the detection device 18, and generate a certain value of voltage, that is, a value indicating the ground fault detection sensitivity. This is to accurately detect the degree of ground fault failure when current is flowing, that is, the insulation resistance of the main engine field circuit with the rotor body. I will explain. FIG. 2 is an equivalent circuit in which a ground fault current i _e flows when a ground fault occurs at point A in FIG. The sum of the field voltage V _f and the rectifier voltage V _D is added to the series circuit of the resistance R of the current limiting resistor 15, the resistance R _c of the detection winding 14, and the insulation resistance R _e of the ground fault point A, and then the field voltage The voltage V _f is connected to a resistor R _f of the field winding 5 so as to cause a current to flow therein. In this way, the value of the insulation resistance R _e is determined from the relationship of equation (101) shown below. R _e ≒ (V _f + V _D )−i _e (R _c +R)/i _e ...
(101) Moreover, by transforming this equation (101), the earth fault current i _e can be obtained as shown in the following equation (102). i _e ≒V _f +V _D /R _e +R _c +R (102) Therefore, the field voltage V _f and the rectifier voltage V _D are the armature voltage of the AC exciter, and therefore the field winding 16
It changes depending on the excitation current flowing through the , and is approximately proportional to the excitation current flowing through the . Since the earth fault current i _e is proportional to the sum of the field voltage V _f and the rectifier voltage V _D as shown in equation (102), it is understood that it is proportional to the excitation current of the field winding 16. Ru. Therefore, the signal detected by the detection device 18 on the stator side is also affected by this. This makes it impossible to know the true insulation resistance R _e . For example, considering the case where the main engine is field facing, V _f +V _D
The value of is increased several times, and even if there is sufficient insulation resistance R _e , the earth fault current i _e shows a large value, and the earth fault current similar to that at the time of a ground fault at normal voltage flows, and the alarm device 21 attempt to malfunction. However, in this embodiment, as described above, the comparison circuit 19 compares the input signal from the detection device 18 and the AC exciter field current. Therefore, the detection circuit 20 can be operated accurately in various cases such as A, B, C, and D in FIG. That is, case A is a case where the field voltage V _f is normal and the insulation resistance R _e is normal. At this time, since the output signal of the detection device 18 is small, the output signal of the comparison circuit 19 is also small, and the detection circuit 20 does not output an output signal. Next, B is a case where the field voltage V _f is abnormally high but the insulation resistance R _e is normal. At this time, the detection device 1
Although the output signal of 8 is large, when the comparator circuit 19 divides or subtracts it by the signal (proportional to the field voltage) generated by the field current of the AC exciter, the output signal of the comparator circuit 19 becomes small, so the detection circuit 20 outputs No signal. Next, C is a case where the field voltage V _f is normal and the insulation resistance R _e is reduced due to a ground fault. At this time, the output signal of the detection device 18 is quite large, but since the signal due to the field current of the AC exciter (proportional to the field voltage) is small, the comparator circuit 19 does not perform large divisions or subtractions and outputs the signal to the detection circuit 20. A large signal is applied, so that the detection circuit 20 outputs an output signal at an operating level. Finally, D is a case where the field voltage V _f is abnormally high and the insulation resistance R _e becomes small due to a ground fault. At this time, the output signal of the detection device 18 becomes very large. Since the signal due to the field current of the AC exciter (proportional to the field voltage) is small, the output signal of the comparator circuit 19 also becomes large. However, in this case, the top part of the output signal is cut off to produce an output signal of the same level as in case C. However, since the output signal naturally exceeds the detection level, the detection circuit 20 outputs an output signal at the operating level. As a result, the detection circuit 20 outputs an output signal at an operating level only when a proper ground fault occurs, and it can be seen that the detection circuit 20 is a highly reliable non-contact detection device. Next, a case where a ground fault occurs at point B of the negative field circuit 7 in FIG. 1 will be explained. If a ground fault occurs at point B, the equivalent circuit will be as shown in Figure 4. Therefore, the ground fault current i _e becomes as shown in equation (103) below. i _e =V _D /R _e +R _c +R (103) In this case, the field voltage V _f is not applied, so A
The element of detection malfunction during main engine field facing is milder than that in the case of a ground fault at a point. However, in this case as well, due to the function of the comparator circuit 19, the relationship shown in FIG. 3 is performed in the same manner as in the case of a ground fault at point A, and detection can be performed without malfunction. Table 1 shows this state as a sample in which each constant is appropriately inserted into each element in FIG.

【table】

【table】

[Table] To put it simply, the detection circuit 20 should operate when the comparison circuit output [1] = ([H]/[B]) > 5, and the detection circuit at both points A and B. It detects whether 20 is 0 or 1, and if it is 0, it is determined that there is no ground fault, and if it is 1, it is determined that there is a ground fault. Furthermore, the detection of the AC exciter field current corresponds to the field forcing operation and only involves dividing by the focusing magnification, so there is no difference in the detection blind spot depending on the presence or absence of the comparison circuit 19. Furthermore, in Table 1, even when there is no ground fault, the ground fault current [K] is slightly generated in the main field winding 5.
This is because the value of the insulation resistance 15 is not infinite, and it is not a problematic value. In this way, according to this embodiment, by simply providing the auxiliary winding 8 in the slot of the AC exciter armature, power can be supplied from the fixed part to the rotating part in a non-contact manner, and the rectifier circuit 9 Because of the above-mentioned configuration, there is no need to apply a voltage higher than the field voltage to the main machine field circuit, and
This has the advantage of preventing malfunction detection due to the setting conditions of the main machine field. Next, a circuit according to a second embodiment of the present invention is shown in FIG. In this figure, the same parts as in FIG. 1 are given the same reference numerals, and their explanation will be omitted. In this embodiment, one phase (or two phases may be used) of the AC exciter armature winding 3 is branched and connected to the primary winding 25 of the transformer 24. The secondary winding 26 electrically insulated is connected to the AC terminals 10, 1 of the rectifier circuit 9.
Connected to 1. The rest is the same as in FIG. In this way, the operation is equivalent to the first embodiment shown in FIG. 1, but the transformer 24
This has the advantage that the voltage can be freely selected and the slot size of the AC exciter armature does not need to be increased. It should be noted that this invention is not limited to the embodiments described above and shown in the drawings, but can of course be implemented with various modifications without changing the gist thereof. As explained above, according to the present invention, ground faults in brushless field circuits can be detected in a non-contact manner, there is no need to apply high voltage to the field circuit for detecting ground faults, and the rotor The parts installed on the side have a simple and simple configuration, and are equipped with a highly reliable non-contact detection device that can prevent detection errors due to load control conditions such as no load, load, and facing of the main synchronous machine. Can be provided at low cost.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing the first embodiment of the non-contact detection device of the present invention, Fig. 2 is an equivalent circuit diagram showing the ground fault current path when a ground fault occurs at point A, and Fig. 3 is the equivalent circuit diagram. FIG. 4 is an equivalent circuit diagram showing a ground fault current path when a ground fault occurs at point B in the first embodiment; FIG. 5 is a diagram of signal waveforms in each part during operation of the first embodiment; FIG. 3 is a circuit diagram showing a second embodiment. DESCRIPTION OF SYMBOLS 1... Stator, 2... Rotor, 3... AC exciter armature winding, 5... Field winding, 6, 7... Field circuit, 8...
Auxiliary winding, 9... Rectifier circuit, 10, 11... AC input terminal, 12, 13... DC output side terminal, 14... Detection winding, 15... Current limiting resistor, 16... AC exciter field winding, 18 ...Detection device, 19...Comparison circuit, 20...
Detection circuit, 21... Alarm device, 22... Current detection device, 24... Transformer, 25... Primary winding, 26... Secondary winding, A, B... Ground fault point, E... Ground point of rotor body, i _e ...Earth fault current.

Claims (1)

[Scope of Claims] 1. In a brushless rotating electrical machine comprising a synchronous machine consisting of a stator and a rotor part, and an AC exciter connected to the synchronous machine, the rotor of the synchronous machine is provided with: (a) an AC exciter; A rectifier circuit that obtains electric power from the armature, connects the electric power to an AC input terminal, and connects the DC output side terminals to the rotor body and the field circuit, respectively; (b) in series with the DC output side of the rectifier circuit; (c) a detection device comprising an inserted detection winding and a current limiting resistor, and disposed on the stator side of the synchronous machine so as to be magnetically coupled to the detection winding; (d) a comparison circuit that compares the output of the detection device and the field current level; (e) a detection circuit that receives the output of the comparison circuit and converts it into a signal for operating an alarm device such as a display, an alarm, or a relay; (f) A current detection device installed in the field circuit of the AC exciter to input the field current or its equivalent signal to the comparison circuit, and detects a ground fault in the event of a field circuit ground fault. A non-contact detection device that detects current. 2. Claim 1, characterized in that the device for receiving power from the armature of the AC exciter to the rectifier circuit is an auxiliary winding provided in a slot in which the armature winding is wound. non-contact detection device. 3. A device in which the rectifier circuit receives power from the armature of an AC exciter has a secondary winding insulated from the primary winding of a transformer whose primary winding is connected to the armature winding. A non-contact detection device according to claim 1, characterized in that: