VSCF Cycloconverter Reliability Review of the 30/40 KVA F/A-18 Electrical Generating System 892228
The United States Navy F/A-18 aircraft uses two 30/40 KVA generating systems to provide precise 400 Hz power to their respective isolated busses. Each generating system is composed of a six phase generator running at a speed proportional to engine rpm, feeding an SCR-based, naturally commutated cycloconverter.
This was the first integral package with shared cooling oil, production, 400 Hz VSCF system. Over 2,000 units have been produced to date. Due to the radical shift from historical, mechanically supplied constant speed technology, the F/A-18 VSCF design initially raised numerous reliability questions. This paper serves to address those concerns and provide development questions with historical field performance/analyses in response.
Reliability predictions using MIL-HDBK-217 procedures are compared to Navy 3-M field performance data over the last eight year production period. Some interesting conclusions are drawn regarding electronic power conversion equipment failure modes, shared oil coolant system performance, and environmental stress-screen effectiveness.