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Power Factor Correction


OBJECTIVE: Develop lightweight and compact equipment to correct leading power factor in a military combat aircraft’s power distribution system. 

DESCRIPTION: The Generator Converter Unit (GCU) is rated at 65kVA, 115V, 400Hz, 3-phase for operation within a power factor range of 0.75 lagging to 1.0 unity. Currently in-flight, the power factor ranges from 0.9 leading to 1.0 unity, which is outside the specification rating range that in turn causes the reliability and life of the GCU to decrease. The leading power factor is caused by capacitance in the avionics' and weapons' Electromagnetic Interference (EMI) filters that are required by MIL-STD-461. In order to offset this capacitance and bring the system's power factor back into operating range, a method to add inductance to the aircraft electrical buses needs to be developed. The combined weight of components of the proposed solution must not exceed 20 pounds, and the footprint of the equipment should be as compact as possible to allow installation on a military combat aircraft. The equipment should correct the power factor from .98 leading to a minimum .97 lagging with a target of .93 lagging while complying with Military Standards 461, 704, and 810 (810 is modified for shock and vibration by MDC3376 spec). The equipment must also turn on and off based on Weight on Wheels input (the system is to be “on” when the weight is off the wheels). The equipment must be able to withstand the environments experienced by a military combat aircraft. 

PHASE I: Design, develop, and demonstrate the feasibility of a system that meets all requirements outlined in the Description. Investigate the effects of the system's total weight, size, target and power factor value and whether the system will be passive or active. Identify and explain how the power factor correction system (operated only while the aircraft is in-flight (weight off wheels)) will be integrated into the aircraft. Prove that the equipment is able to withstand the environments experienced by a military combat aircraft. Develop either the inductor rating if the system is passive or develop the range of inductance and the sensing system required to change its inductance value if the system is active. The Phase I effort will include prototype plans to be developed under Phase II. 

PHASE II: Develop a prototype that is capable of being added onto an aircraft electrical bus and should demonstrate the desired power factor correction during flight by utilizing the passive or active method determined in Phase I. The prototype should be small and light enough to be installed on military combat aircraft platforms with minimal impact to aircraft weight. The unit should be tested with a system to show a change in power factor from .98 leading to at least .97 lagging. 

PHASE III: Test the product to ensure an acceptable transition for use on a military combat aircraft. Aircraft are constantly adding more avionics that are leading loads due to the required capacitive EMI filters. Eventually, enough leading loads will be added to the aircraft that the whole system will become leading. F/A-18 is the first to reach this point but other platforms like P-8 and E-2D, or any other military or commercial aircraft could benefit from the SBIR-developed technology in the future. Industries that utilize generators, such as the shipping industry, could benefit from this technology. 


1: Dugan, R., McGranaghan, M. & Beaty, H. "Electrical Power Systems Quality, Third Edition." The McGraw-Hill Companies, Inc., 2012.

2:  "IEEE Recommended Practice for Electric Power Distribution for Industrial Plants." (IEEE Std 141-1993). Std 141-1993 Red Electric Power Distribution for Industrial Plants

3:  MIL-STD-461, Military Standard: Electromagnetic Interference Characteristics Requirements for Equipment.

4:  MIL-STD-704, Military Standard: Electric Power, Aircraft, Characteristics and Utilization of.

5:  5. MIL-STD-810, Military Standard: Environmental Engineering Considerations and Laboratory Tests.

KEYWORDS: Power Factor; Power Distribution; Leading; F/A-18; Inductance; Lagging 


Clifford Moll 

(301) 342-0880 

Charles Singer 

(301) 342-0815 

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