DEVELOPMENT OF DEFINITIONS AND LIMITS FOR FREQUENCY TRANSIENTS AND FREQUENCY MODULATION IN AIRCRAFT 380- TO 420-CPS ELECTRIC SYSTEMS
Phase rept. no. 2,
NAVAL AIR DEVELOPMENT CENTER WARMINSTERPA AERONAUTICAL ELECTRONIC AND ELECTRICAL LAB
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The report discusses the problem and requirements for adequate instrumentation, and establishes definitions and limits for the transient- frequency and frequency-modulation characteristics of constant-frequency aircraft electric systems. The instrumentation evaluation emphasized the need for improved instrumentation to measure both frequency transients and frequency modulation. The improvements are basically in the area of 1 Measuring frequency accurately from the voltage output of a generator while the measurements are kept independent of voltage fluctuations. 2 Improving the time constant so that rates of frequency change up to 500 cpss can be recorded accurately. 3 Improving sensitivity to frequency deviation so that frequency modulation can be recorded in a readable and accurate manner. The study of the data of frequency transients has indicated that limits can be defined in terms of envelopes grouped in overall conditions correlated to electric system actions. To be compatible with utilization equipment designers requirements, definition of frequency modulation should be expressed in terms of rate of frequency change and total limit of modulation.