Electricity: electrical systems and devices – Safety and protection of systems and devices – Generator protective circuits
Patent
1982-12-15
1985-01-08
Salce, Patrick R.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Generator protective circuits
361 86, 322 29, 322 58, H02H 706
Patent
active
044929994
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a supervisory unit for rotary electrical machinery and apparatus by which abnormal phenomena appeared on shaft voltage of the rotary electrical machinery and apparatus such as synchronous machine and the like are detected.
TECHNICAL BACKGROUND
In synchronous machines, voltage of several volts--ten-odd volts generates on the rotating shaft due to imbalance in magnetic flux or magnetomotive force, accumulation of charge derived from fluid in a turbine, grounding of the coil or the like. Such shaft voltage breaks down oil film on the shaft bearing and shaft current flows therethrough so that the bearing is damaged. Shaft voltage contains AC component and DC component, and the AC component involves mainly synchronous machine fundamental frequency (primary one: 50 Hz or 60 Hz) and synchronous machine tertiary harmonic wave (150 Hz or 180 Hz).
In the case where an excitation device of brushless excitation system type is employed, power source frequencies of the AC exciter appear as the AC component, while almost the same frequencies as that of the synchronous machine come out in the case where a thyristor type exciting device is used.
Heretofore, such a means in which a brush is allowed to contact with its shaft and a voltage across the shaft and the ground is determined has been known as a means for supervising shaft voltage of such type of synchronous machines. If a brushless turbine generator is taken as an example, the generator is constructed such that usually an earthing brush is mounted on its turbine side, and at the same time another brush is permitted to contact with a shaft of a brushless exciter on the opposite side of the turbine or a shaft of the turbine generator on the side of the brushless exciter to connect the brush with the ground through a resistance circuit, whereby a voltage value across both ends of the resistance circuit is detected to supervise abnormality in value of such shaft voltage.
However, in such supervisory unit as mentioned above, when the resistance circuit is short-circuited or when the brush becomes uncontacted with respect to the shaft, the shaft voltage cannot be detected and therefore, reliability of such supervisory unit is poor as the one for brushless synchronous machines.
DISCLOSURE OF THE INVENTION
A supervisory unit for rotary electrical machinery and apparatus according to the present invention is provided with a detector for obtaining a voltage signal across at least two points of a rotor shaft, another detector for obtaining a voltage signal between the rotor shaft and the ground, still another detector for detecting an electrical signal of a constituent on the field system side of the rotary electrical machinery and apparatus, and an abnormality detector for giving a signal of abnormality at the time when values of voltage and frequency of the shaft voltage are abnormal on the basis of the detection signals of these detectors. Accordingly, the supervisory unit for rotary electrical machinery and apparatus by which supervision of such shaft voltage can positively be effected, and causes for or positions of abnormal phenomena can be determined or discriminated may be obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a constructional diagram illustrating a brushless synchronous machine to which a supervisory unit for rotary electrical machinery and apparatus according to the present invention is applied;
FIG. 2 is a constructional diagram illustrating the present invention; and
FIGS. 3 and 4 are constructional diagrams illustrating other embodiments of the present invention.
THE MOST PREFERRED MODE FOR EMBODYING THE INVENTION
FIG. 1 is a view for illustrating a construction of a brushless synchronous machine which is to be used for the present invention in which the synchronous machine (1) involves an armature (2) and a field system (3), and rotors of an AC exciter (5) and a subexciter (6) are directly connected to a rotor shaft (4) to integrally construct the machine. Furthermore, reference charact
REFERENCES:
patent: 4074180 (1978-02-01), Sharpe et al.
patent: 4329637 (1982-05-01), Kotake et al.
patent: 4377780 (1983-03-01), Bjorklund
Mitsubishi Denki & Kabushiki Kaisha
Salce Patrick R.
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