JPH0634564B2 - Ground fault detector for generator - Google Patents

Description

TECHNICAL FIELD The present invention relates to a ground fault detector for a generator, and more particularly to a non-contact rotor coil ground fault detector for a brushless generator.

"Prior Art" Conventionally, a rotor coil ground fault detection device in a brushless generator has, as shown in FIG. 6, a secondary coil 2 of a power transformer 1 for supplying a power source for ground fault detection, a rotor core. The primary coil 4 of the ground fault detection device 3 including a rotary transformer and the current limiting resistor 5 are connected in series to the secondary coil 2, and one end of the series circuit is grounded to the rotary shaft or the spider.
The other end was connected to the main generator field coil 6. In addition, 7
Is an exciting coil, 8 is an armature coil, 9 is a rotary rectifier, 1
Reference numeral 0 is a stator coil, and 11, 12 and 13 are output terminals.

In such a configuration, when a ground fault occurs in the field coil 6 of the main generator as indicated by the dotted line, it passes through the secondary coil 2 for power supply, the primary coil 4 for ground fault detection, and the current limiting resistor 5, A current of about 100 mA flows to the ground, and this current is detected by the ground fault detection device 3, and the detection signal drives a relay or the like to interrupt the circuit.

"Problems to be solved by the invention" However, since the ground fault detection device was conventionally composed of a rotary transformer, the device became large in size, and it was intended for devices with medium or more capacity. Was difficult to install, and therefore a small brush had to be installed to detect a ground fault, and could not be completely brushless using a sharp brushless exciter.

"Means for Solving Problems" The present invention relates to the stator core 19 of the AC exciter, the field coil 7 and the field coil 7.
And the armature coil 8 is provided on the rotor core 14 of the AC exciter, and the armature coil 8 is coupled to the field coil 6 of the main generator via the rotary rectifier 9 to obtain the field of the main generator. In an AC generator in which an AC power source is obtained from a stator coil 10 magnetically coupled to a magnetic coil 6, the rotor core 14 is provided with π / n at intervals of 2π / n (n is a positive integer, hereinafter the same). N ground fault detection power supply coils 15 to be single-phase generators are arranged in slots within the range of 1., one end of these power supply coils is coupled to the field coil 6 of the main generator, and the other end is connected to the rotor core. 14 grounded to the stator core 19 and 2n sets of ground fault detection coils 20 spanning the NS poles at intervals of π / n.
Are arranged so as to detect the voltage due to the magnetic flux of the ground fault detection power supply coil 15 in any one of the groups, and the ground fault detection coils 20 have opposite phases in order to cancel the influence of the magnetic flux due to the armature coil 8. And a combination detection unit 23 that outputs a ground fault detection signal to the output side of the synthesis unit 21 by comparing the output of the synthesis unit 21 with a set value.
A ground fault detection device for a generator, characterized in that

[Operation] The magnetic pole of the exciter is, for example, 12 poles, and the two ground fault detection power supply coils 15 are separated by π / 2 at intervals of a central angle π (180 degrees).
Arranged within the range of (90 degrees), four ground fault detection coils 2
0s are arranged at intervals of a central angle π / 2 (90 degrees), and π
Two pairs are formed by series-connecting each other at (180 degrees). That is, the ground fault detection coil 20 is made up of two sets in which opposing coils are connected in series, and the phases are opposite to each other.
Then, before the occurrence of the ground fault, even if a voltage is induced by the magnetic flux of the armature coil 8, the combined current of the two becomes substantially zero in the combining unit 21. When a ground fault occurs here, the power supply coil for ground fault detection 15, the field coil 6 of the main generator, the rotating shaft 16 or the spider 17, the current limiting resistor 5, and the closed circuit returning to the power supply coil 15 are configured. Therefore, during the operation of the generator, a current of several 10 mA to several 100 mA flows through the power supply coil 15, a voltage is induced in the ground fault detection coil 20 four times in one rotation, and the voltage is output to the synthesis unit 21. Then, this voltage is compared to the comparison detection unit 23.
Is compared with the set value, and the output turns on the transistor 24, activates the relay 25, and disconnects the circuit.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. The same parts as those in FIG. 6 are designated by the same reference numerals.

In FIG. 1, 7 is a field coil of an AC exciter, and 8 is a three-phase armature coil. This armature coil 8
It is coupled to the field coil 6 of the main generator via a three-phase full-wave rotary rectifier 9. Further, 10 is a stator coil of the main generator, and 11, 12, 13 are output terminals.

The rotor core 14 around which the armature coil 8 is wound is fixedly provided on the spider 17 on the outer periphery of the rotary shaft 16 as shown in FIG.
... are provided at equal intervals. The armature coil 8 is inserted in the slot 26 ...
Two coils 15 of the ground fault detection power supply coil 15 are provided in the slots 26 with an interval of 180 degrees and a central angle of 90 degrees or less.
a and 15b are arranged in a single layer winding, respectively, and as a whole, 2
It has a layered structure.

As shown in FIG. 1, one end of the ground fault detection power supply coil 15 is connected to the rotary shaft 16 or the spider 1 via a current limiting resistor 5.
7, and the other end is connected to the field coil 6 of the main generator via a rotary rectifier 18.

The stator core 19 of the AC exciter is composed of twelve field pole cores 19 at equal intervals, and these field pole cores 19 ...
Is wound with the field coil 7, and the four coils A1 and B1 of the ground fault detection coil 20 span the NS pole of the field pole core 19 ... And are spaced 90 degrees apart.
A2 and B2 are arranged.

The ground fault detection coils 20 are arranged at intervals of 90 degrees.
Of the coils A1, B1, A2, B2, the first and third coils
It is composed of a coil A in which coils A1 and A2 are connected in series and a coil B in which second and fourth coils B1 and B2 are connected in series, and these coils A and B are electrically connected in opposite phases. One end of each of these coils A and B is a synthesizing section 21.
Further, the synthesizing unit 21 is coupled to the comparison detecting unit 23 via the amplifying unit 22, and the comparison detecting unit 23 is coupled to the circuit breaking relay 25 via the driving transistor 24.

The operation of the above configuration will be described.

When a current flows through the armature coil 8 during normal rotation before occurrence of a ground fault, a voltage as shown in FIG. 3 (a) is generated in each of the coils A and B of the ground fault detection coil 20. However, since the coils A and B of both sets have opposite polarities and are input to the two input terminals of the combining unit 21, the output of the combining unit 21 is substantially zero as shown in FIG. Next to
Even if amplified by the amplifier 22, the comparison detector 23 does not reach the set value and the relay 25 is not driven.

Here, when a ground fault occurs as shown by the dotted line in FIG. 1, the power supply coil for ground fault detection 15, the rectifier 18, the field coil 6 of the main generator, the spider 17, the rotary shaft 16, and the current limiting resistance 5 are passed. A closed circuit for returning to the power supply coil 15 is formed, and a current of several tens mA to several hundred mA flows in this closed circuit. Then, in the ground fault detection coil 20, an induced voltage due to the magnetic flux of the armature coil 8 and an induced voltage due to the magnetic flux of the power supply coil 15 are generated.

In the ground fault detection coils A and B, the voltages due to the magnetic flux of the armature coil 8 cancel each other out, but the voltage due to the magnetic flux of the power supply coil 15 is applied to only one of the ground fault detection coils A and B, for example, Since the voltage is induced only in the set of the ground fault detection coils A, the voltage is induced once at 90-degree intervals as shown in FIG. 3 (c). This voltage is amplified by the amplification unit 22, compared with the set value by the comparison detection unit 23, the transistor 24 is turned on, the relay 25 is operated, and the circuit is cut off.

1 and 2, the armature coil 8 is wound in a single layer in the slot 26, and the power supply coil 15 is inserted in the same slot 26 in a single layer to form two layers. Therefore, the external appearance is the same as that of the two-layer winding AC exciter, and the size is almost unchanged. However, although slightly larger than the single layer winding, it is also possible to make each a two-layer winding coil and assemble the coil into four layers in the same slot.

In the embodiment of FIGS. 1 and 2, the ground fault detection coil 20
Was divided into four and incorporated at 90 degree intervals, and the power supply coil 15 was divided into two and incorporated at 180 degree intervals. With such a configuration, it is possible to eliminate the influence of device manufacturing and assembly. However, it is not limited to this. For example, as shown in FIG.
180 in the slot 26 of the armature core 14 as only one
Installed within the range of degrees, the ground fault detection coils 20 are installed in two sets of two A and B, and are attached across the NS poles at intervals of 180 degrees. With this configuration, when a ground fault occurs, a voltage due to the magnetic flux of the power supply coil 15 is induced only twice during one rotation.

Further, as shown in FIG. 5, the power supply coil 15 includes 15a,
15b, 15c divided into 3 parts, 120 degree intervals, 60
Installed in the slot 26 within the range of degrees, the ground fault detection coil 2
0 is divided into three sets of A1, B1, C1, A2, B2, and C2, and is installed over the NS pole at 60-degree intervals. With this configuration, when the ground fault occurs, the power coil 1
A magnetic flux of 5 induces a voltage 6 times.

"Effects of the Invention" (1) Since the power supply coil 15 for ground fault detection is incorporated in the rotor core 14, a power supply for ground fault detection is not required.

(2) When the ground fault detection power supply coil 15 is incorporated in the rotor core 14, the power supply is not required, but the ground fault detection coil 20 detects the magnetic flux of the armature coil 8 regardless of the presence or absence of the ground fault. However, the phases are made opposite to each other by the armature coil 8.
It is possible to cancel a large current of 0 to 200 A and reliably detect a small current of 100 to 200 mA by the ground fault detection power supply coil 15.

(3) With respect to the ground fault signal, since the change in the magnetic flux of the ground fault detection power supply coil 15 incorporated in the rotor core 14 is detected by the ground fault detection coil 20 incorporated in the stator core 19,
The structure is simpler and smaller than conventional rotary transformers.

(4) The ground fault detection power supply coil 15 can be miniaturized without the need for a special power supply transformer by forming a single-layer winding two-layer arrangement together with the armature coil 8.

(5) Since the ground fault detection coil 20 is used for detection, the reliability is extremely high without being affected by electrical noise or other disturbances.

(6) Since the ground fault current does not pass through the bearing metal, a highly reliable detection device can be obtained, and it can be applied to not only large capacity but also medium capacity and small capacity generators.

[Brief description of drawings]

1 is an electric circuit diagram showing an embodiment of a ground fault detecting device for a generator according to the present invention, FIG. 2 is a front view of a rotor and a stator,
FIG. 3 is an output waveform diagram of the ground fault detection coil, FIGS. 4 and 5 are front views of different embodiments of the present invention, and FIG. 6 is an electric circuit diagram of a conventional device. 1 ... Power transformer, 2 ... Secondary coil, 3 ... Ground fault detection device, 4 ... Primary coil, 5 ... Current limiting resistance, 6 ... Field coil, 7 ... Field of exciter Coil, 8 ... Exciter armature coil, 9 ... Rotary rectifier, 10 ... Stator coil, 11, 12, 13 ... Output terminal, 14 ... Rotor armature core, 15, 15a, 15b ... … Power supply coil for ground fault detection, 16 …… Rotation axis, 17 …… Spider, 18 …… Rectifier, 19 …… Stator field magnetic pole core, 20, A, B, A
1, B1, A2, B2, C1, C2 ... Ground fault detection coil, 21 ... Synthesis section, 22 ... Amplification section, 23 ... Comparison detection section, 24 ... Transistor, 25 ... Relay, 26 ...
…slot.

Claims (3)

[Claims] 1. A stator core 19 of an AC exciter is provided with a field coil 7, a rotor core 14 of the AC exciter is provided with an armature coil 8, and the armature coil 8 is connected via a rotary rectifier 9. In an AC generator which is coupled to the field coil 6 of the main generator, and an AC power source is obtained from a stator coil 10 magnetically coupled to the field coil 6 of the main generator, the rotor core 14 is provided with 2π. / N (n is a positive integer, the same applies below) are arranged in slots within the range of π / n with n ground fault detection power supply coils 15 to be single-phase generators. 2n sets of ground fault detection coils 20 are connected to the field coil 6 of the main generator, the other end is grounded to the rotor core 14, and the stator core 19 spans NS poles at intervals of π / n.
Are arranged so as to detect the voltage due to the magnetic flux of the ground fault detection power supply coil 15 in any one of the groups, and the ground fault detection coils 20 have opposite phases in order to cancel the influence of the magnetic flux due to the armature coil 8. And a combination detection unit 23 that outputs a ground fault detection signal to the output side of the synthesis unit 21 by comparing the output of the synthesis unit 21 with a set value.
A ground fault detection device for a generator, characterized in that 2. The armature coil 8 and the ground fault detection power supply coil 15 are each incorporated in the slot 26 of the rotor core 14 by a single layer winding so that the external appearance is the same as that of the two layer winding. The ground fault detection device for a generator according to item 1. 3. A ground fault detecting device for a generator according to claim 1, wherein 2n ground fault detecting coils 20 are connected in series every time they face each other.