JPS61161937A - Brush malfunction detector of synchronous machine - Google Patents

Abstract

PURPOSE:To detect the spark of a brush and an improper contact by a simple circuit by detecting the variations in the exciting voltage and current, calculating the variation in the resistance value of a field winding circuit, and judging as a brush malfunction when the value exceeds the prescribed range. CONSTITUTION:In a circuit for supplying an exciting current through a collector ring 3 and a brush 4 to the field winding 2 of a synchronous machine 1, the values of an exciting voltage Vf and a current If are detected through insulating converters 7, 8. The detected values vf and if are input to a detector 9, vf/if is calculated to obtain the resistance value of a field winding circuit. When the calculated value exceeds the prescribed range, it is judged that a malfunction occurs between the ring 3 and the brush 4 to generates an alarm AL.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a brush abnormality detector for a synchronous machine that monitors a spark phenomenon occurring between a collector ring and a brush in a synchronous machine and the contact state thereof.

[Technical background of the invention and its problems] In a synchronous machine, a system having a collector ring for supplying excitation current to a field winding and a brush installed to slide on the collector ring has a problem in that the sliding If moving parts are poorly maintained, problems may occur due to spark phenomena such as sparks, arcs, or flashovers, or poor contact. Within a short period of time, this problem develops into an accident in which brushes or collector rings are burnt out, and the accident further escalates into abnormal vibration of the synchronous machine rotor and field loss.

Therefore, in order to prevent such accidents, conventional measures have been taken, such as detecting sparks using a phototube, or detecting the field supply voltage and detecting the degree of spark generation using a vacuum tube voltmeter. .

However, these methods have the following problems. That is, in the former case, since the detection section is a phototube, effective arrangement is not possible for a synchronous machine with a large number of brushes due to structural constraints, and a large number of detection sections are required. Also, due to detection sensitivity constraints, it is useless if the spark generation point is far away.On the other hand, when the latter is applied to a synchronous machine, the output of the rectifier that supplies the field voltage has a sharp waveform. is included, resulting in false positives. Furthermore, since all of these devices detect the spark itself, there are problems in that the devices are complicated and expensive.

[Object of the invention] The present invention provides a brush abnormality detector for a synchronous machine that can detect sparks generated between the collector ring and the brushes or their contact state using a simple circuit and an inexpensive detector. With the goal.

[Summary of the Invention] The present invention detects sparks or contact between the collector ring and the brushes due to the field voltage and field current supplied to the field winding of a synchronous machine, by reducing the apparent resistance value of the field winding. The feature is that it is detected as a change.

[Embodiment of the Invention] The present invention will be described below with reference to an embodiment shown in the drawings.6 Fig. 1 is a configuration diagram showing an embodiment of the present invention, and the synchronous machine 1 can be roughly divided into a stationary part and a stationary part. It consists of a rotating part.

A field winding 2 and a collector ring 3 are arranged in the rotating part. The field winding 2 is supplied with a rectified DC voltage Vf from a rectifier 5 via a collector ring 3 and an external brush 4 that slides on the collector ring 3. The field voltage Vf between the slip rings is input to the detector 9 via the isolation converter 8 as vf, and the field current If is input via the shunt 6 and the isolation converter 7 to the detector 9 as if.

The detector 9 is composed of a divider 9a, a comparator 9b, a time delay 9c, and a relay circuit 9d, as shown in FIG. The divider 9a calculates vf/if=Rf using the input signals vf and if, and detects the apparent resistance Rf of the field winding 2.

FIG. 3 shows an equivalent circuit around the brush of a synchronous machine, where Q2 represents the reactance of the field winding 2, and r2 represents its resistance. When a spark or arc occurs or when the contact between the collector ring 3 and the brush 4 is poor, the contact resistance r between the collector ring 3 and the brush 4 increases, and the apparent resistance Rf of the field winding 2 increases.
increases. This Rf is compared with a set level by a comparator 9b, and if it exceeds a certain level, the relay 9d operates with a certain time delay 90.
Give an alarm or display ^L.

Note that the apparent resistance Rf of the field winding 2 changes depending on changes in the ambient temperature and the operating state of the synchronous machine, so the comparator 9b needs to be set so as to escape these levels.

FIG. 4 is a block diagram showing another embodiment of the brush abnormality detector, in which vf and if are compared by a comparator 9b.

When there is an abnormality around the brush due to spark generation or poor contact, Rf increases due to contact resistance and the ratio of vf/if changes, so the comparator 9b operates. Even in this case, the same effect as described above can be obtained.

[Effects of the Invention] As described above, according to the present invention, sparks (arc, spark) generated around the brushes of a synchronous machine and the contact state between the brushes and the collector ring are effectively detected, and an alarm or display is issued. It becomes easier to take measures such as automatically stopping the operation of the synchronous machine, and it also prevents the continuation or expansion of poor contact and spark generation, and prevents further damage to the synchronous machine. .

[Brief explanation of the drawing]

FIG. 1 is a control block diagram of the brush area of a synchronous machine showing an embodiment of the present invention, and FIG. 2 is an internal block diagram of a brush abnormality detector.
FIG. 3 is an equivalent circuit diagram around the brush of a synchronous machine, and FIG. 4 is an internal configuration diagram of a brush abnormality detector showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Synchronous machine, 2... Field winding, 3... Collector ring, 4... Brush, 5... Rectifier, 6...
Shunt, 7, 8... Isolation converter, 9... Detector,
9a...Divider, 9b...Comparator, 9
c...Time delay, 9d...Relay circuit. (7317) Agent: Patent Attorney Noriyuki Chika (
(and 1 other person) Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] In a synchronous machine in which a field current is supplied to a rotor equipped with a field winding through a collector ring and brushes, sparks and poor contact between the collector ring and brushes are detected, and changes in excitation voltage and current are detected. A brush abnormality detector for a synchronous machine, characterized in that the change is detected as a change in the resistance value of the field winding, and when the resistance value exceeds a predetermined range, it is determined that a brush abnormality has occurred.