Spacecraft Single Phase AC Electrical Power

When single-phase power is pulled from a 3-phase supply (e.g., for Orbiter lighting) that 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 sense 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.