ANSI/IEEE 251-1984 pdf free download.IEEE Guide: Test Procedures for Direct-Current Tachometer Generators.
ANSI/IEEE 251-1984 covers instructions for conducting and reporting the more generally applicable and acceptable tests to determine the performance characteristics of direct-current tachometer generators. Direct-current tachometer generators are used for a variety of indicating and control purposes and a characteristic of primary importance in one application may be of little or no importance in another. This procedure shall not be interpreted or construed as requiring the making of all or any of the tests herein in any given transaction.
2. Tests-General
2.1 Normal Test. Because of the variety of applications and of design and manufacturing conditions, it is beyond the scope of this pro cedure to define a normal test. However, a large number of machines normally are built with the same design, possibly with minor mechanical modifications, and as a result certain performance tests have been grouped frequently enou Igh to result in the following definitions.
These are listed merely as a guide and do not constitute a specification.
3.2 Ammeters. Direct-reading indicating instru ments, either analog or digital type, are ordin arily sufficiently accurate for reading load current. The instrument should be so selected that readings will be well up on the scale, preferably at least 75% of full-scale reading The accuracy requirements for measuring field current of separately excited tachometer generators are the same as those for measurin output voltage and similar instruments shall be used.
3.3 Tachometer Generator Drive. For most of the tests, the only satisfactory drive is a syn chronous motor. The motor should have a rating several times the maximum torque requirement of the tachometer generator and should be well damped to minimize the effects of voltage variations in the power supply and torque variations in the tachometer generator.
3. Test Equipment
3.1 Voltmeters. Direct-reading indicating instruments, either analog or digital type, ma be used for some tests where the specified tolerances are large compared with the instru ment accuracy. When an indicating instrument is used, it should be selected so that readings will be well up on the scale, preferably at least 75% of full-scale value. For many of the tests, the permissible deviations in the tachometer generator voltage are of the same order of mag nitude as the precision of the best indicating instruments. For these tests a null-balance potentiometer type direct-current voltmeter having an accuracy at least 4: 1 better than the maximum voltage deviation to be measured shall be used.ANSI/IEEE 251-1984 pdf download.