1、Public Lessons Learned Entry: 4057 Lesson Info: Lesson Number: 4057 Lesson Date: 2010-09-16 Submitting Organization: KSC Submitted by: Annette Pitt Subject: Spacecraft Single Phase AC Electrical Power Abstract: When single-phase power is pulled from a 3-phase supply (e.g., for Orbiter lighting) that
2、 is feeding critical 3-phase motors, there is a resulting phase imbalance (especially neutral leg current) that can disrupt instrumentation that is monitoring the health of other equipment. This instrumentation monitors the current draw of the motor (or an associated load such as a fluid pump) to se
3、nse motor loading that may indicate when a bearing is wearing out, a pump is stalling, or there are short or open circuits. Whenever possible, dedicated 3-phase power should be provided to critical rotary equipment to alleviate this problem. Description of Driving Event: Each Orbiter fuel cell power
4、 plant (FCP) that provides electrical power to the Orbiter has two pumps as part of its balance-of-plant. These include a coolant pump that circulates coolant through the FCP to control the operating temperature and a water separator/hydrogen circulation pump (H2O/H2 pump) that helps remove water fr
5、om the FCP and circulate humidified GH2 through the FCP. Each pump runs on 3-phase AC current provided by Orbiter inverters. The H2O/H2 pump has a pump motor condition (PMC) sensor integrated into the motor assembly to provide insight into the H2O/H2 pump loading as well as provide feedback when a m
6、otor stalls or there is a current phase loss. Sensor output is obtained by monitoring all three input phases as well as the common return (neutral leg) for changes in current flow. The differences are summed and then converted into a 05 VDC signal that can be monitored. Shuttle engineers have long k
7、nown that Orbiter electrical equipment operating on a single-phase of a 3-phase supply (e.g., Orbiter lighting) can produce a phase imbalance that distorts readings on the PMC sensor. During several launch countdowns, the sensor picked up phase imbalances that were not caused by the FCP but made the
8、 motor suspect nonetheless. As a result, significant time and effort were spent investigating these anomalies only to determine that they were caused by normal operation of equipment external to the FCP. Lesson(s) Learned: Having a sensitive sensor that relies on obtaining 3-phase current phase imba
9、lances to provide insight into the status of a given piece of equipment can give false indications when the 3-phase current affects other equipment being operated. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Shuttle Orbiter Fuel Cell Powerplant R
10、ecommendation(s): In the future, either develop a sensor that is not subject to distortions caused by other equipment or provide a dedicated source of electrical power to the equipment being monitored. Evidence of Recurrence Control Effectiveness: N/A Documents Related to Lesson: N/A Mission Directo
11、rate(s): Science Exploration Systems Space Operations Additional Key Phrase(s): Vehicle concepts Reliability Test & Verification Engineering design and project processes and standards Level II/III requirements definition Mission and systems trade studies Crew Survival Systems Lander Systems Orbiting
12、 Vehicles Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Quality Product Assurance Launch support systems Power Spacecraft and Spacecraft Instruments Spacecraft Review systems and boards Energy Flight Operations Hardware Independent Verification and Validation Launch Vehicle Additional Info: Project: Space Shuttle Program Approval Info: Approval Date: 2011-07-22 Approval Name: mbell Approval Organization: HQ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
