IEEE 112:2017 pdf free download – IEEE Standard Test Procedure forPolyphase Induction Motors andGenerators
4.3.1 Power
Mechanical power measurements shall be taken with the greatest care and accuracy. If a mechanical brakeis to be used, the tare, if present, shall be carefully determined and compensated for. If dynamometer outputmeasurements are used, coupling and bearing friction losses must be compensated for.An in-line torquetransducer may be used to provide a direct measurement of torque at the test machine shaft. Properly sizeddynamometers should be used, such that the coupling,friction, and windage losses of the dynamometer(see the note below) measured at rated speed of the machine being tested should not be greater than 15% ofthe rated output of the machine being tested; and the dynamometer should be sensitive to a change oftorque of 0.25% of the rated torque.
NOTE—A dynamometer is defined as a device for applying torque to the rotating member of the test machine. It isequipped with means for indicating torque and speed, and is not limited to a cradle base construction.6
The errors of the instrumentation used to measure mechanical torque shall not be greater than +0.2% of fullscale.Additionally, for Efficiency Test Methods A and B, the operating range for the instrumentation shallbe selected such that at rated full-load of the motor under test, the total error for torque measurements shallnot exceed =0.7% of the reading，which shall include all errors from all sources (load cell, torque armlength, etc.).The error of the instrumentation can be validated by calibration as a system or by calculationfrom the square root of the sum of the squares of the individual instrument errors. See Annex E forinformation on determining the total error of measurements.
The detecting element should be located on or in close thermal proximity to the part at which the localtemperature is to be measured to obtain the highest temperature for that item, except for the incoming anddischarge air or other coolant temperature, for which it should be placed to obtain the average value.
Specially designed instruments should be used with local temperature detectors to prevent the introductionof significant errors or possibly damaging the detector during the measurement. Because of the variety ofmaterials used in these detectors，take care to ensure the instrument selected is suitable for the specificmaterial used in the detector or is matched to the resistance value when resistance thermometers are used.Many ordinary resistance measuring devices may not be suitable for use with resistance thermometersbecause of the relatively large current that may be passed through the resistance element while making themeasurement.
4.4.1.3 Embedded detector
Embedded detectors,such as resistance temperature detectors (RTDs) or thermocouples， are commonlyused on large machines to monitor the winding temperature during operation and are available for useduring machine testing.They are usually installed between coil sides within a stator slot.An RTD gives areading that is the average of the temperature of the two abutting coil sides over the length of the sensingelement. A thermocouple measures the temperature of the spot where the thermocouple junction is locatedbetween the two coil sides.
The precautions on the selection of instrumentation in 4.4.1.2 also apply here.
4.4.1.4 Winding resistance
The average temperature of a winding can be determined by comparing the resistance of the winding at thetemperature to be determined with the resistance at a known temperature. This method utilizes thecharacteristic of the conductor material where, in the temperature range of interest, the winding resistancechanges in direct proportion to the winding temperature. See 5.3.2.