Abstract: A diagnostic system for an electrical generator winding which has first and second passages for conduction of cooling gas. The temperature of the gas exiting the passages is determined and converted to a normalized value which may be either high, low or normal. A diagnostic computer determines the existence of predetermined combinations of high, low or normal for the two readings and these predetermined combinations are utilized by the computer which generates respective confidence factors in the existence of certain abnormal generator conditions such as open conductors, broken or blocked cooling gas passages, and sensor malfunctions, by way of example.

Abstract: A generator having stator windings which are water cooled includes a plurality of sensors each for measuring the temperature of cooling water as it is discharged from respective sections of the stator windings and prior to its collection in a common manifold. The outputs of the sensors are combined to obtain an average reading and during an initialization process, each sensor reading is subtracted from the average to derive a correction factor for that particular sensor, for that particular average. The generator is operated so that other averages are selected for the calculation of other sensor correction factors. When operating on line, the correction factors are utilized to obtain a value for a percent of average coil temperature in accordance with the relationship: ##EQU1## where T is the temperature indication provided by the sensor, AVG is the average of all of the sensor readings, and CF is the appropriate correction factor for that sensor for that average.

Abstract: Insulated multiphase electrical windings are tested by applying to both ends of one phase, a positive DC voltage for a fixed period of time and simultaneously to another phase an equal negative DC voltage is applied for the same fixed period of time and all remaining phases are grounded. The application of the positive and negative DC voltages is repeated until each phase of the multiphase windings has been tested with both a positive and negative voltage.