GB1008933A - Improvements in and relating to dynamo-electric machines - Google Patents

Abstract

1,008,933. Fault testing. C.A.PAISONS & CO. Ltd. Feb. 14,1964 [April 1, 1963], No. 12764/63. Heading G1U. Means for detecting faults in rotor windings of dynamo-electric machines whilst the rotor is revolving comprises an electrical network in which each coil of the rotor winding is represented by an element; the voltage drop across each element, when supplied with a standard current, being equal to or in fixed relationship to the calculated voltage drop across the corresponding rotor coil when supplied with a standard current; and means for comparing the voltage drop across each rotor coil and its associated element to detect and/or record any departure from the fixed relationship. In Fig. 2 rotor coils 1 within a rotor body R are provided with tappings 4 connected to a selector switch 14 by leads passing through a bore or bores in the rotor shaft. The two ends of a set of coils are connected through slip rings 16 to a battery 9 and the circuit may include a variable resistance and an ammeter so that the current can be adjusted to a desired value. A plurality of elements 2, each comprising a fixed resistance in series with a variable resistance, are energized by a battery 8 and connected to a selector switch 17 operated in synchronism with switch 14 so that the potential across a coil 1 is balanced against the potential across a corresponding element 2 at the input of the detector 19. The detector 19 may comprise an input switch 19d, an amplifier 19a, a filter 19b and a recorder 19c. A relay 24 controls the energization of solenoids 15 and 18 which operate selector switches 14 and 17, and a relay 25 controls switch 19d. The two relays may be energized via cams 20 and 21 driven by a motor 22 and arranged so that the detector 19 is inoperative during the change-over times of switches 14 and 17. The rotor can be rotated at any speed during testing. The slip rings 16 may be the main rotor slip rings or slip rings provided for testing purposes; the slip rings 16a and 16b providing connections to the switch 14 and the solenoid 15 may be instrument slip rings.