JP2874998B2 - Synchronous machine field circuit ground fault detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention] (Industrial application field) The present invention relates to a field circuit ground fault detecting device of a brushless synchronous machine.

(Prior art) A high-sensitivity field ground detector is installed in the field circuit of a synchronous machine so that if a ground fault occurs, it will be detected before a fatal short circuit occurs for the machine. doing. This design philosophy is followed regardless of type, such as a brushless type and a non-brushless type.

 FIG. 3 shows a configuration example of a conventional apparatus.

In the figure, a portion (1) surrounded by a two-dot chain line indicates a rotating portion, and an AC exciter armature winding (2) is generated by exciting an AC exciter field winding (3) in a stationary portion. AC power is rectified by a rotary rectifier (4), supplied to a synchronous machine field winding (5), and has a main circuit configuration in which a voltage is generated in a synchronous machine armature winding (6).

On the other hand, regarding the configuration of the field circuit ground fault detecting device, the AC voltage generated in the AC exciter armature auxiliary winding (7) installed in a slot (not shown) for the AC exciter armature winding (2) Is rectified by an auxiliary power rectifier (8), one end of the direct current is grounded on a rotating part (1) at a ground point (E), and the other end is passed through an exciting coil (9) to synchronize the field of the synchronous machine. Circuit conductor (1
0) Connect on top. Then, a detection coil (11) is provided at a stationary portion facing the excitation coil (9), and this is connected to a ground fault detector (12).

In this configuration, the synchronous machine field magnetic circuit conductor (10)
When a ground fault occurs, the rectifier for auxiliary power supply (8)
As a result, a ground-fault current is generated from the ground-fault point (1a) to the ground point (E) in a loop, and a ground-fault current flows through the exciting coil (9) according to the ground-fault level, thereby generating magnetic flux. This magnetic flux rotates at the same speed as the rotating part (1), and the magnetic flux interlinks with the stationary detection coil (11) grounded on the opposite side. Input to (12). When this input voltage exceeds a certain level, a ground fault detector (12)
Operates by detecting that a ground fault has occurred, and generates a signal for urging an external circuit to warn or stop. FIG. 4 is a diagram showing an outline of a mounting structure of the exciting coil (9) and the detecting coil (11). The rotating section includes a synchronous machine field circuit conductor (10) as a positive field and a negative field. It comprises magnetic conductors (14) and (15), a rotating frame (17) and an exciting coil (9) mounted on the rotating frame.

Further, a detection coil (11) is provided at a position facing the exciting coil (9) in the stationary portion. That is, the detection coil (1
The exciting coil (9) rotates around 1) according to the speed of the synchronous machine. FIG. 5 is a side view of the detection coil (11) and the excitation coil (9) viewed from the direction of arrow "A" in FIG. ) Indicates a rotating state.

In this state, when a current flows through the exciting coil (9), a magnetic flux φ is generated in the direction indicated by the arrow in FIG.
By interlinking with 1), a pulse-like waveform as shown in FIG. 6 is generated in the detection coil (11).

The ground fault detector (12) detects that this level has exceeded a predetermined value, and detects that a ground fault has occurred.

(Problems to be Solved by the Invention) This conventional field circuit ground fault detection device has a very high sensitivity function of detecting the ground fault current at DC 3 mA or more. On the other hand, this characteristic is weak against noise.

For example, as shown in FIG. 4, when the positive and negative field conductors (14) and (15) are installed close to the detection coil (11), the positive field conductor In (14), a field current flows from the ground fault point (1a) to the negative field conductor (15) in the direction of the arrow in FIG. 4 to generate a magnetic flux.

In the case of FIG. 4, the magnetic flux is applied to the detection coil (1
1) occurs in a direction that penetrates from the front side to the back side of the paper. When this magnetic flux rotates along with the rotation of the rotating part, it interlinks with the detection coil (11), and a substantially sinusoidal commercial frequency voltage as shown in FIG. 7 is induced in the detection coil (11). At this time, since the absolute value of the voltage is proportional to the magnitude of the field current, when the load on the synchronous machine increases or when the power factor is operated in the delay direction, the detection sensitivity of the ground fault detector (12) is reduced. The detection operation is performed in spite of no ground fault abnormality.

The present invention has been made in view of the above circumstances, and does not malfunction due to noise generated during normal operation, maintains excellent high sensitivity characteristics when a field ground fault occurs, and appropriately and easily detects abnormality. It is an object of the present invention to provide a synchronous machine field circuit ground fault detecting device for performing the same.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, according to the present invention, first and second ferromagnetic materials are provided around a field conductor serving as a noise source near a detection coil. Constitute a magnetic circuit surrounded by members, and
A synchronous machine field circuit ground fault detecting device having an air gap or a non-magnetic member in the magnetic circuit, wherein a second ferromagnetic member is disposed between the synchronous machine field circuit conductor and the detection coil. provide.

(Operation) By applying the above means, the relative permeability of the ferromagnetic member is as large as several hundred to several thousand with respect to the relative permeability of 1 for the air gap.
Most of the magnetomotive force due to the field current flowing through the field conductor is consumed in the air gap, and behind the ferromagnetic member where the detection coil is located, the noise is reduced by reducing the strength of the magnetic field behind it. That is, the S / N ratio, which is the ratio between the signal S and the noise N, is improved. Therefore, by setting the detection level to a predetermined value or more, an abnormality can be appropriately detected when a field circuit ground fault occurs, and the function of the synchronous machine field circuit ground fault detection device, which has been unable to perform its function sufficiently due to a malfunction, conventionally. Function can be enhanced.

(Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1 and FIG.

FIG. 1 shows a gap (g ₁ ) around the positive and negative field conductors (14) and (15) of the synchronous machine field circuit conductor (10).
First, second ferromagnetic member has a _{(g 2) (23),} (24)
And the detection coil (11) is installed on the outer surface of the substantially central portion of the second ferromagnetic member (24) in proximity to and behind the substantially circular opposing area (16) shown by a dashed line. Indicates that you have done. One of the first and second ferromagnetic members (23) and (24), or a part thereof, may be shared by a conventional structural material. The gaps (g ₁ ) and (g ₂ ) may be only one of them, or may be any non-magnetic member. Other parts are the same as those shown in FIGS. 3 and 4 as the conventional example.

 Next, the operation of this embodiment will be described.

FIG. 2 shows equipotential lines (25) and (26) of a magnetic field due to a field current flowing through the synchronous machine field circuit conductor (10) when viewed from the arrow B in FIG. However, only half of the space on the side where the detection coil (11) is located with respect to the ferromagnetic member (23) is shown. The equipotential line (25) shown by a broken line is a conventional case without the second ferromagnetic member (24), and extends radially from the synchronous machine field circuit conductor (10). The detection coil (1
The strength of the magnetic field at the position 1) is represented by the interval between the equipotential lines (25) and (26) at that position. The equipotential line (26) shown by a solid line is a case where the second ferromagnetic member (24) according to the present embodiment is installed. The number of equipotential lines (26) is the same as the conventional one, but the distribution is significantly different from the conventional one. That is, while the relative magnetic permeability of the air gaps (g ₁ ) and (g ₂ ) is 1, the non-magnetic permeability of the ferromagnetic member (24) is as large as several hundreds to several thousands, so that the positive side and the negative side Field conductor (14),
Most of the magnetomotive force surrounding (15) is spent in the air gaps (g ₁ ) and (g ₂ ). That is, most of the equipotential lines are concentrated there, and the ferromagnetic member (2
In the vicinity of 4), a small number of equipotential lines (2
6), the spacing is widened and the strength of the magnetic field is reduced. This allows the positive or negative field conductor (14)
Alternatively, the noise component to the detection coil (11) due to the field current flowing through (15) is reduced, and the S / N ratio is improved.

[Effects of the Invention] As described above, according to the present invention, even when commercial frequency noise is loaded on the detection coil due to a structural cause, the ground fault detecting device does not always respond to the noise. It is possible to provide a synchronous machine field circuit ground fault detection device that can respond to a pulse-like voltage when a field circuit ground fault occurs and can appropriately detect the field circuit ground fault.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main part of an embodiment of the present invention, FIG. 2 is an equipotential diagram as viewed in the direction of arrow B in FIG. 1, FIG. 3 is a circuit diagram according to the prior art, and FIG. Third by technology
FIG. 5 is an explanatory view for explaining the principle of FIG.
FIG. 6 is a mounting diagram of the exciting coil and the detecting coil as viewed from the arrow, FIG. 6 is an output voltage waveform diagram of the detecting coil of FIG. 3, and FIG. 7 is a commercial frequency voltage waveform diagram induced by the detecting coil of FIG. DESCRIPTION OF SYMBOLS 1 ... Rotating part 1a ... Earth fault point 2 ... AC exciter armature winding 3 ... AC exciter field winding 4 ... Rotary rectifier 5 ... Synchronous machine field winding 6 ... Synchronous machine Armature winding 7 ……………………………………………………………………………………………………………………… ………………………………………………………………………. ... Positive field conductor 15... Negative field conductor 16... Opposite range of detection coil 23... First ferromagnetic member 24.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-77359 (JP, A) JP-A-55-164378 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H02K 19/00-19/38

Claims (1)

(57) [Claims] A rotating armature type AC exciter is provided, the output of which is rectified by a rotary rectifier, and used as a field source for a synchronous generator or a synchronous motor. When a field circuit is grounded, an auxiliary power supply and a circuit are connected. A brushless synchronous system comprising an exciting coil formed and generating a magnetic flux outside the rotating part, a detecting coil detecting the magnetic flux at a stationary part, and a ground fault detector receiving an output of the detecting coil and detecting a ground fault. In the field circuit ground fault detecting device of the machine, a magnetic circuit surrounding a synchronous machine field circuit conductor serving as a noise source near the detection coil with first and second ferromagnetic members is formed, and A synchronous machine field circuit ground fault detecting device, wherein the magnetic circuit has an air gap or a non-magnetic member, and the second ferromagnetic member is arranged between the synchronous machine field circuit conductor and the detection coil.