72kW PD High Level changes to B809E PD.docx

Attached is the Purchase Description from the previous 72kW Ground Power Unit (GPU) Acquisition. Immediately below are the more important changes for the current 72kW GPU acquisition.

· Power Output Changes:

· 60Hz simultaneous with all other power outputs

· Alone and simultaneous with all other power outputs

· 120 VAC

· Single phase

· Two (2) NEMA 5-20R convenience receptacles each providing up to 20 amps

· Meet the 60 Hz requirements of MIL-STD-704, except:

· Voltage shall be 120 VAC vs 115 VAC

· All MIL-STD-704 60 Hz voltage requirements shall be centered on 120 volts

· Simultaneous 28.5 VDC and 400 Hz 115 VAC power outputs

· Combined outputs of 60Hz, 400 Hz, and 28.5 VDC shall be no less than 72kW

· Environmental:

· Operating temperature range: -40 degrees Fahrenheit to +130 degrees Fahrenheit

· Full power altitude requirement: Sea level at +130 degrees Fahrenheit to 6,500 feet at +90 degrees Fahrenheit

· Storage temperature range: - 50 degrees Fahrenheit to + 160 degrees Fahrenheit

· The GPU shall be capable of operating at 119o F with 36 percent humidity

· Acoustical Noise: The acoustical noise of the GPU shall be no greater than 84 dBA

· Material: The GPU enclosure and doors shall be made of aluminum

· Powder Coat: The GPU shall be powder coated instead of painted

· Fuel Tanks: contain sufficient fuel to provide no less than 12 hours of usable fuel for continuous operation at 80% load

· Emergency Stop Button Location: An emergency stop push-button shall be provided in the control panel area for easy access, but shall be outside the control panel doors. The emergency stop shall be recessed to prevent accidental activation.

(Continued on next page)

EXPORT CONTROLLED INFORMATION

WARNING - This document contains technical data whose export is restricted by the Arms Export Control Act (Title 22, U.S.C., Sec 2751, et seq.) or the Export Administration Act of 1979, as amended, Title 50, U.S.C., App. 2401, et seq. Violations of these export laws are subject to severe criminal penalties. Disseminate in accordance with provisions of DoD Directive 5230.25.

· Starting: The GPU shall meet the starting requirements in the following table

Four (4) hours of heat from an externally powered winterization system

5 minutes

Four (4) hours of heat from an externally powered winterization system 30 minutes of external devices such as: External power (jump starting); external heaters; external blowers; etc.

10 minutes

INCH POUND

72 kW / 90 kVA GENERATOR SET

PURCHASE DESCRIPTION

1.0 SCOPE

1.1 Coverage. This document covers the requirement for a 72 kW / 90 kVA generator set, herein referred to as Ground Power Unit (GPU). The GPU is used to provide 115/200 and 230/400 VAC 400 Hz, 28 VDC, and 270 VDC external ground power for United States Air Force (USAF) aircraft such as the A-10/OA-10, AC-130H/U, B-1B, B-2, B-52, C-5, C-17, CV-22, C-130E/H/J/J-30, F-15A/B/C/D/E, F-16A/B/C/D, F-22, F-35, HC-130P/N, KC-10, KC-135, LC-130H, MC-130E/H/P/W, MH-53J/M, UH-1N, WC-130J, and other assorted general purpose and trainer aircraft for various ground based maintenance activities. The GPU shall be the latest state of the art design and shall comply with the requirements of this document unless specified otherwise by the governing contract.

2.0 APPLICABLE DOCUMENTS

2.1 General. The documents listed in this section are specified in Sections 3, 4, or 5 of this specification. This section does not include documents cited in other sections of this specification or recommended for additional information or as examples. While every effort has been made to ensure the completeness of this list, document users are cautioned that they must meet all specified requirements of documents cited in Sections 3, 4, or 5 of this specification, whether or not they are listed.

2.2 Government documents.

Comments, suggestions, or questions on this document should be addressed to: WR-ALC/642 CBSG/GBEA, Robins AFB, GA 31098-1813. Since contact information can change, you may want to verify the currency of this address information using the ASSIST Online database at www.dodssp.daps.mil.

Comments, suggestions, or questions on this document should be addressed to: WR-ALC/LEEG, Robins AFB, GA 31098-1611. Since contact information can change, you may want to verify the currency of this address information using the ASSIST Online database at www.dodssp.daps.mil. C N/A

EXPORT CONTROLLED INFORMATION

WARNING - This document contains technical data whose export is restricted by the Arms Export Control Act (Title 22, U.S.C., Sec 2751, et seq.) or the Export Administration Act of 1979, as amended, Title 50, U.S.C., App. 2401, et seq. Violations of these export laws are subject to severe criminal penalties. Disseminate in accordance with provisions of DoD Directive 5230.25.

AMSC N/A FSC 6115

Distribution Statement D. Distribution authorized to the Department of Defense (DoD) and U.S. DoD Contractors only; Critical Technology, 8 October, 2008. Other requests shall be referred to 642 CBSG/GBEA.

2.2.1 Specifications, standards, and handbooks. The following specifications, standards, and handbooks of the exact revision listed below form a part of this specification to the extent specified herein.

FEDERAL STANDARDS

DEPARTMENT OF DEFENSE SPECIFICATIONS

DEPARTMENT OF DEFENSE STANDARDS

DEPARTMENT OF DEFENSE HANDBOOKS

COMMERCIAL ITEM DESCRIPTIONS

A-A-59745 Zinc-Rich Coatings

(Copies of these documents, except for MIL-HDBK-1791 C-17 Appendix, are available online at http://assist.daps.dla.mil/quicksearch/ or from the Standardization Document Order Desk, 700 Robbins Avenue, Building 4D, Philadelphia, PA 19111-5094. A copy of MIL-HDBK-1791 C-17 Appendix can be obtained form the Procuring Contracting officer (PCO) or requested by contacting the Air Transportability test Loading Agency (ATTLA) at 937-255-6296.)

2.3 Non-government publications. The following documents of the exact revision listed below form a part of this document to the extent specified herein.

American National Standards Institute (ANSI)

ANSI C2 2007 National Electrical Safety Code

(Application for copies should be addressed to ANSI, 1819 L St. NW, 6th Floor, Washington, DC 20036, www.ansi.org.)

Burton Electrical Engineering

5PTV6002-101 Connector, Plug/Cable Assy, Elec, External Power, 270 VDC, 70 KW

(Application for additional information should be addressed to Burton Electrical Engineering, 1510 W. 135th St, Gardena, CA 90247-6862, www. burtonee.com.)

J and B Aviation Services

(Application for additional information should be addressed to J&B Aviation Services, 907 Cotting Lane, Suite A, Vacaville, CA 95688, www.jandbaviation.com.)

National Electrical Manufacturers Association (NEMA)

(Applications for copies should be addressed to NEMA, 1300 North 17th Street, Suite 1847, Rosslyn, VA, 22209, www.nema.org.)

National Fire Protection Association (NFPA)

NFPA 70 2008 National Electric Code

(Application for copies should be addressed to NFPA, Batterymarch Park, Quincy, MA 02169-7471, www.nfpa.org.)

Society of Automotive Engineers (SAE)

(Application for copies should be addressed to SAE, Inc., 400 Commonwealth Drive, Warrendale, PA 15096, www.sae.org.)

Underwriters Laboratories, INC. (UL)

UL 489 2006 Molded Case Circuit Breakers & Circuit Breaker Enclosures

(Application for copies should be addressed to UL, 333 Pfingston Rd, Northbrook, IL, 60062-2096, www.ul.com.)

Vantage Technology

V-70840-PMR-RFI-L36 SD Panel Mount Receptacle

(Application for additional information should be addressed to Vantage technology, 4675 South Windermere St, Englewood, CO 80110, www.vantagexp.com.)

2.4 Order of precedence. Unless otherwise noted herein or in the contract, in the event of a conflict between the text of this document and the references cited herein (except for related specification sheets), the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained.

3.0 REQUIREMENTS

3.1 First article. When specified (see 6.2), two (2) first article GPUs shall be subjected to first article verification in accordance with 4.2.

3.2 General. The GPU shall be a stand alone, trailer mounted, self-contained unit capable of providing aircraft quality external ground power. Specifically, the GPU shall be capable of providing: three phase 115/200 volts alternating current (VAC), re-connectable to 230/400 VAC at 400 Hz rated to continuously provide 72 kW / 90 kVA of electrical power; 28.5 volts direct current (VDC) rated to continuously provide 17 kW of electrical power; 270 VDC rated to continuously provide 72 kW of electrical power. Multiple types of electrical power are not required to be available simultaneously. The GPU shall be constructed of modular and easily replaceable subassemblies and components wherever possible. The GPU enclosure shall be suitable for full time outdoor use and be four wheel trailer mounted. The enclosure shall have doors to provide access for maintenance, repair, and replacement of modular components and subassemblies. Components of the GPU shall be UL recognized or listed whenever possible. Additional features and capabilities shall be permitted unless otherwise prohibited by this document.

3.3 Generator design. The generator shall be directly coupled to the engine. Single bearing machine mounting and coupling shall minimize the effects of misalignment and torsional vibration. Double bearing machine couplings shall be of the vibration dampening type to minimize the effects of misalignment and torsional vibration. The generator shall be of a brushless design; excitation shall be supplied from a brushless exciter as well. Temperature rise shall be in accordance with the limits set forth in NEMA MG-1 for Class F or H insulation; vacuum impregnated epoxy resin or a similar process shall be used to ensure long-term insulation effectiveness. Temperature rise of the bearing(s) shall not exceed 90 degrees Fahrenheit. Insulation resistance shall not be less than 2 mega-ohms in an ambient temperature of 77 degrees Fahrenheit. The generator shall be of the drip-proof guarded type and meet all applicable standards of NEMA MG-1 and MG-2. The generator shall be capable of operation at 125% rated speed for at least 15 minutes without electrical or mechanical damage. Electrical windings shall have the following dielectric strength (withstand the following 400 Hz voltages applied for one minute):

a. Armature. 1,832 volts between phase windings and 1,480 volts between phase windings and ground.

b. Field and Exciter Windings. 10 times ceiling voltage but shall not be less than 1,500 or more than 3,500 volts between windings and ground.

c. Windings Energized by DC Voltages (control, starting, sharing systems). 500 volts between windings and ground; windings shall be insulated to Class F or H standards using a void free 100% solids epoxy vacuum pressure impregnation or similar process.

d. All others. Twice rated voltage plus 1,000 volts applied between windings and ground and between windings when applicable.

The GPU generator and excitation systems shall be capable of withstanding a 10 second duration single phase line to neutral, single phase line to line, and symmetrical 3 phase short while operating at rated load. Reduction in dielectric strength shall not be allowed. Short circuit current is defined as not less than 300% of rated full load current. The GPU shall be configured such that neither symmetrical nor asymmetrical faults will cause damage.

3.4 Output electrical power. The GPU shall provide the output power characteristics listed below. All output power shall be available individually; there is no simultaneous AC and DC electrical output power requirement and there is no simultaneous DC and DC electrical power output requirement, i.e. no AC/DC requirement at the same time and no DC/DC requirement at the same time. Unless otherwise explicitly stated, all external ground power requirements herein are to be met at the aircraft interface (cablehead/receptacle).

3.4.1 AC output power requirements. The power requirements listed in this section concern the main AC power output as utilized on A-10/OA-10, AC-130H/U, B-1B, B-2, B-52, C-5, C-17, CV-22, C-130E/H/J/J-30, F-15A/B/C/D/E, F-16A/B/C/D, HC-130P/N, KC-10, KC-135, LC-130H, MC-130E/H/P/W, WC-130J, and other assorted general purpose and trainer aircraft for various maintenance activities.

3.4.1.1 AC output voltage and frequency. The GPU output voltage shall be three phase, 115/200 VAC re-connectable (via the use of a reconnect board) to 230/400 VAC, wye configured with a grounded neutral. The output voltage shall be regulated to 1% at all settings from zero to full load. The GPU output frequency shall be 400 Hz, regulated to ± 0.5% at all loads. The DC component in the output voltage shall not exceed 0.1 volts and the crest factor shall be 1.31 to 1.51. The GPU shall operate as specified with a delta or wye configured load. The GPU shall be pre-set from the factory for 115/200 VAC output. The GPU control panel shall be equipped with a fine voltage adjustment device (non-locking potentiometer with a knob for tool-less adjustment) with an approximate 300 degree rotation (clockwise increase/counterclockwise decrease) to allow an approximate +/-2.5 VAC voltage output voltage adjustment for various aircraft voltage requirements. This device shall work in conjunction with the line drop compensation feature and voltage adjustment requirements of 3.4.9 and 3.4.10 herein. Depending upon the contractors design, this device may also work in conjunction with the 28.5 VDC and 270 VDC outputs of 3.4.2.1 and 3.4.2.2 (albeit with differing voltage adjustment scales).

3.4.1.2 Output power rating. The GPU shall meet the requirements set forth herein and any additional requirements contained in MIL-STD-704. The GPU shall have a continuous output power rating of 72kW / 90kVA; the GPU shall be capable of providing continuous power into a load with a power factor between 0.95 leading and 0.8 lagging. All applicable tolerances stated herein and in MIL-STD-704 shall be met with the output voltage preset to 115 (L-N) or 230 (L-N) at the cable head under all load conditions including transients.

3.4.1.3 Output phase sequence. The phase sequence of the GPU output voltage shall be a positive sequence of A-B-C (AB-BC-CA).

3.4.1.4 Phase balance. The output voltage for each phase shall be balanced (within 1%) while the GPU is operating at full load (with 0.8 power factor lagging or 0.95 leading), no load, or any load in between. For a three phase unbalanced load not exceeding 15% (see 3.4.1.5 herein) the load unbalance shall not exceed 3.33% of the total three phase load.

3.4.1.5 Unbalanced loads. The GPU shall be capable of supplying a 15% maximum unbalanced load. The unbalanced load of 15% shall be defined as one of the three phases at its full load condition and the remaining two phases at 85% of their full load condition. Under this condition the difference between any of the three phase to neutral voltages shall be no greater than 3.5%.

3.4.1.6 Phase angle regulation. The displacement angle between adjacent voltages shall be 120 degrees ( 2 degrees) for the balanced load and shall be 120 degrees ( 4 degrees) for the three phase 15% unbalanced load.

3.4.1.7 Amplitude modulation. The GPU (voltage) amplitude modulation shall not exceed 1% for no load to full load conditions.

3.4.1.8 Frequency stability. The GPU frequency regulation shall be independent of the load changes. The frequency stability of the GPU shall be at a minimum 0.5% (400 Hz) for all load conditions.

3.4.1.9 Line drop compensation. The GPU shall provide the specified voltage at the end of interfacing cable assemblies described as 115 VAC, 260 amp rated 60 foot output power cable (SAE AS 90328-34) or equivalent and at the end of a 230 VAC, 130 amp rated 60 foot output power cable (SAE AS 21378-15) or equivalent as required by MIL-STD-704 and herein. The GPU shall provide both a manual line drop compensation adjustment and an automatic line drop compensation (ALDC) adjustment to compensate for line drop loses in the output power cables. The GPU shall have a switch to manually select the compensation method used; the selector switch device shall be located away from the normal operator interface either via locked menu, cabinet door, or similar means. The line drop compensation circuit shall provide full voltage adjustment over the entire range of generator set operating voltage. While in the ALDC mode of operation the GPU shall sense the output voltage in two selectable locations, local and remote (see 3.4.1.10 herein). The GPU shall provide a minimum of 10% voltage adjustment through both manual and automatic line drop compensation. Note: in certain installations the use of a 125 foot single jacket 115 VAC 260 amp rated cable described as JB8817-125NJ, Contractor and Government Entity (CAGE) 0SMN2 is required; the line drop compensation circuit shall provide enough adjustment range to overcome line losses in this cable at a full 260 amp load. While operating in the ALDC mode of operation, utilizing the remote sense function of 3.4.1.10 herein, the GPU shall provide the specified voltage as required by MIL-STD-704 and herein at the cable head of the AC aircraft cables referenced herein.

3.4.1.10 Sensing. The GPU shall be equipped to operate with local and remote sensing while in the ALDC mode of operation. In local sensing mode the output voltage shall be sensed at the AC output cable terminals or the main 400 Hz buss of the GPU, dependent upon contractors design. In remote sense mode the output voltage shall be sensed at the load end of the AC output cable. The local or remote selector switch shall be located away from the normal operator interface via locked menu, cabinet door, or other similar means. When operating in remote sensing mode the GPU shall automatically revert to local sense mode if a break occurs in the sensing wires. Note that current sensing is also an acceptable method of providing ALDC. If current sense is used in the contractors ALDC design only a remote sense function with an “ON” and “OFF” device is required.

3.4.1.11 Output transient recovery. The GPU transient output voltage recovery shall be in accordance with MIL-STD-704 Figure 3 and the output frequency transient recovery shall be in accordance with MIL-STD-704 Figure 5.

3.4.1.12 AC overload. The GPU shall open the output contactor when the output current exceeds 125% (± 2%) on any phase for more than 30 seconds. Overload capacity between 100 and 125% shall be based on the inverse time delay curve principle.

3.4.1.13 Short circuit. The GPU shall be protected against a short circuit across the output AC cable and shall disconnect power from the load buss within 25 milliseconds in the event of a short circuit in any output phase.

3.4.1.14 Total harmonic distortion (THD). The THD in the output voltage for the GPU, regardless of ancillary power supplies, motors, etc that may be operating on the GPU, shall be as follows:

a. Balanced load condition: From no load to full load, the Root Mean Square (RMS) sum of all THD components in the output voltage waveform line-to-line and line-to-neutral shall not exceed 3% of the RMS value of the rated voltage. Maximum single harmonic distortion shall not exceed 2% RMS of the fundamental at the nominal voltage under the above listed conditions. Additionally, there shall be no spikes or notches in the output waveforms.

b. Unbalanced load condition: THD shall not exceed 4% (RMS) line-to-neutral with a 15% unbalanced load applied.

3.4.1.15 28 VDC aircraft interlock E/F circuit. The GPU shall have selector switches (located on the control panel in the vicinity of the output contactor control devices) labeled as "GPU LOOP-BYPASS-AIRCRAFT LOOP" to control the E/F pin interlock circuit for each individual output device. Note: two switches with one labeled as “GENERATOR POWER-AIRCRAFT POWER” and the other labeled as “LOADBANK” are also acceptable for each individual output device. The GPU shall contain terminal block points for the connection of 12 AWG wires from the aircraft cable assemblies for the interlock circuit. The GPU E/F interlock circuit shall not be sensitive to the polarity of the DC current flowing to and from the aircraft. When the DC current goes to zero, for any reason, the output contactor in operation shall open within 25 milliseconds. The GPU shall accept an unfiltered half-wave rectified 28 VDC signal, but an intermittent signal shall not be permitted. For descriptive purposes below the “28 VDC signal” below is the nominal steady state value, actual values may range from 16 to 32 volts with 28 +2/-4 volts being the most common steady state values. In “AIRCRAFT LOOP” mode, before the interlock loop is complete the voltage sent to the GPU may be a very choppy sine-wave like waveform approaching 60 volts. The GPU shall be capable of receiving and providing at least 5 amps of continuous current, and as much as 10 amps to close the E/F pin relay contacts.

In the “AIRCRAFT LOOP” mode, the GPU shall close the output contactor for a period of four to six seconds at start up. The GPU shall receive a 28 VDC signal from the aircraft on the F pin and loop it back to the aircraft via the E pin. This loop shall be monitored by the GPU to determine if a 16 to 32 VDC signal is present. When present, the output contactor shall remain closed. When this signal is not present or drops out the output contactor shall open (within 25 milliseconds).

In the “BYPASS” mode the E/F pins may be connected together but are not monitored or grounded. The E-F pin circuit is not used to control the output contactor. Any changes required to operate in the “BYPASS” mode shall be automatically implemented.

In the “GPU LOOP” mode, the GPU shall close the output contactor for a period of four to six seconds at start up. The GPU shall provide a filtered and regulated 28 VDC signal to the aircraft via pin E. If the 28VDC signal is looped back on the F pin, then the output contactor shall remain closed. If the voltage is not present on pin F, then the output contactor shall open (within 25 milliseconds).

3.4.1.16 AC power cable. Each production GPU shall be shipped with one 115 VAC 260 amp rated capacity, 60 foot, extra flexible, single jacket cable assembly featuring a molded cable head with strain relief and replaceable nose section. If remote voltage sensing is utilized in the line drop compensation method of the GPU control system the cable shall also be equipped with sensing wires. Further, the cable shall be equipped with E/F sensing lines; these lines shall not be "jumpered" at the cable head. The cables shall be part number JB8817-60 (with RVS) CAGE 0SMN2, or JB8816-60NJ (without RVS) CAGE 0SMN2, or equivalent; note that the Government shall have final approval authority on cable equivalency. See 6.3 c. herein for additional information on interfacing assemblies. Production GPUs are not required to ship with the 230 VAC cable.

3.4.2 DC power supplies. The 28 VDC and 270 VDC power supplies shall be all solid-state designs using the latest technology for the generation and control of the DC power output. The DC power supplies shall utilize methods to obtain an efficiency of at least 90% at full load conditions and at least 85% at half load conditions. The DC power supplies shall be an integral part of the GPU and designed for continuous outdoor use. The converters shall be air-cooled and designed for easy access, so that any necessary adjustments, part replacements, cable connections, and controls can be accessed through the cabinet or enclosure of the GPU through maintenance panels or doors. All DC power supply inputs shall be from the GPU AC generator output. Each DC power supply shall be equipped with input surge protection to protect the solid-state components from damage due to any unexpected input transient voltages. Each DC power supply shall be designed to place less than 5% input THD on the AC generator over the entire output load range of the DC power supplies, unless the design approach is such that greater than 5% THD will not negatively affect the AC generation system (AC generator windings). The DC power supplies shall be equipped with soft-start circuitry on the respective internal DC buses to limit inrush current to less than 110% of the power supply input current at full-load output. The soft-start circuitry shall automatically charge the power supply internal DC bus upon application of AC power to the converter. The DC power supplies shall also be equipped with a thermal protection system to prevent damage incurred by overheating. Note that isolation between the 270 VDC and associated 28 VDC interlock returns and the AC generator neutral may be required, depending upon the contractors design approach.

3.4.2.1 28.5 VDC requirements. The 28.5 VDC power requirements listed in this section concern the main 28.5 VDC power output as utilized for MH-53J/M, UH-1N, and other assorted general purpose and trainer aircraft for various maintenance functions. The 28.5 VDC power supply is not required to be active when the GPU is reconnected to provide 230/400 VAC, 400 Hz output or 270 VDC output.

3.4.2.1.1 Output voltage. The DC power supply output voltage shall be 28.5 VDC (nominal). The output voltage shall be manually adjustable a minimum of 10% (at the GPU, away from the normal operator interface via locked menu, cabinet door, or other similar means) to compensate for output cable losses. The DC power supply shall also operate in conjunction with the fine voltage adjust feature described in 3.4.1.1, above. Additionally, the DC power supply shall be regulated to 1% at all settings from zero to full load. The 28.5 VDC performance requirements specified herein shall be met when operating with the worst-case combination of input line conditions and worst-loads specified herein.

3.4.2.1.2 Output power cable. The GPU shall be designed to operate with a 28.5 VDC 60 foot output power cable SAE AS 90347-22 or equivalent. Note: the Government shall have final approval authority on cable equivalency. See 6.3 c. herein for additional information on interfacing assemblies. Production GPUs are not required to ship with the 28.5 VDC cable.

3.4.2.1.3 Output power rating. The DC power supply shall be capable of providing 600 continuous amps of 28.5 VDC electrical power into a load (approximately 17 kW at 28.5 VDC). Additionally, the DC power supply shall be capable of providing 2000 amps for 30 seconds every 30 minutes for use in starting aircraft. Duty cycle, time on, and power availability shall be appropriately reduced at amperages exceeding 600; see 3.4.2.1.7 herein. Additionally, the voltage is allowed to drop below the 28.5 VDC steady state limits when amperages exceeding 600 are provided, however, in no instance shall the voltage ever drop below 12 VDC, which is the starting voltage lower limit of MIL-STD-704.

3.4.2.1.4 Ripple voltage. Ripple voltage on the DC power supply output voltage shall not exceed 1.5 volts (peak to peak) for no load to full load condition.

3.4.2.1.5 Transient output voltage. The DC power supply transient output voltage recovery shall be in accordance with MIL-STD-704 Figure13.

3.4.2.1.6 Distortion factor. The DC power supply distortion factor shall be no greater than 0.035. The DC power supply distortion spectrum shall be in accordance with MIL-STD-704 Figure 15.

3.4.2.1.7 28.5 VDC overload. The DC power supply shall open the output contactor if the current exceeds 660 amps for more than 30 seconds or if the output current exceeds 1500 amps for 10 seconds. Overload capacity between 600 and 2000 amps shall be based on the inverse time delay curve principle with the two points of interest noted above being on the curve.

3.4.2.1.8 Short circuit. The DC power supply shall be protected against a short circuit across the output DC cable and shall disconnect power from the load buss within 25 milliseconds in the event of a short circuit. The short circuit protection circuit shall work in conjunction with the overload limits of 3.4.2.1.7 herein and shall be defined as not less than 300% rated load.

3.4.2.1.9 Current limiting. The DC power supply shall have a current limiting device, controlled by an “ON-OFF” switch, for use with the jet engine starting feature. Current limiting shall be adjustable via potentiometer type device from at least a 750 to 1500 amp range.

3.4.2.2 270 VDC requirements. The 270 VDC requirements contained in this section cover the main 270 VDC external ground power used for maintenance purposes on the F-22 and F-35 aircraft, including conventional take off and landing (CTOL), short take off and vertical landing (STOVL), and carrier (CV) variants. All 270 VDC requirements shall be met at the aircraft interface (cablehead/receptacle) when the standard 270 VDC external power cable is in use. All requirements shall be met with the worst case combination of input voltage and worst case load condition. Throughout this section common 270 VDC external power system performance requirements, F-22 specific requirements, and F-35 specific requirements are presented. Additionally, the 270 VDC power supply is not required to be active when the GPU is reconnected to provide 230/400 VAC, 400 Hz output or the 28.5 VDC output.

3.4.2.2.1 Output voltage The continuous rated power supply output voltage shall be 270 VDC, regulated to ± 1% at all settings from zero to full load at the cable head. Additionally, the 270 VDC power supply shall continue to provide the minimum cable head voltage required during overload conditions described in 3.4.2.2.10 and 3.4.2.2.11 herein.

3.4.2.2.2 Output power cable. The GPU shall be designed to operate with a 270 VDC, 267 amp rated capacity, 63 foot, extra flexible, multiple conductor, single jacket cable assembly. The interfacing cable assembly shall be part number 5PTV6002-101, CAGE 81861 or equivalent; note that the Government shall have final approval authority on cable equivalency. See 6.3 c. herein for additional details of interfacing assemblies. See Appendix A for 270 VDC cable to aircraft interface requirements. Production GPUs are not required to be shipped with the 270 VDC cable.

3.4.2.2.3 Output power rating. The 270 VDC power supply shall be rated to continuously provide 267 amps DC into a load (approximately 72 kW at 270 VDC). The power supply shall comply with all loading, overloading, and transient requirements herein.

3.4.2.2.4 Ripple amplitude. Output voltage ripple amplitude for the 267 amp 270 VDC output shall be as defined in Table I below.

TABLE I. 270 VDC Normal operating characteristics.

3.4.2.2.5 Distortion. The 270 VDC distortion factor and spectrum shall meet the requirements of Table I herein.

3.4.2.2.6 Output transient voltage. The 270 VDC output shall remain within the range of 220 to 330 VDC under the worst case combination of input voltage step change and any output load step change within the range of 300-0-300 amps DC, inclusive of the load profiles defined herein, for either positive or negative 200 amps per millisecond current rate of change. Voltage transient onset occurs when the output voltage, to include allowed voltage ripple, exceeds 270 ± 2.7 VDC for a duration greater than or equal to 0.5 milliseconds. The 270 VDC power supply output shall begin recovery from onset of the worst case transient excursion within 10 milliseconds and shall be completely recovered within 40 milliseconds. See Figure 1, below for complete details of the transient voltage limits.

FIGURE 1. Envelope of normal voltage transient for 270 volts DC system.

3.4.2.2.7 Line drop compensation. If needed by the contractor’s design the 270 VDC power supply may incorporate an ALDC function on the main 270 VDC output to maintain the minimum voltage input thresholds at the aircraft external power receptacle, effectively cancelling out the voltage drop in the 270 VDC output cable. Note that the 270 VDC cable contains no sensing wires for remote voltage sensing applications.

3.4.2.2.8 28 VDC aircraft interlock C/D cable interlock circuit. The 270 VDC power supply shall be equipped with a cable interlock, similar in nature to a conventional E/F interlock, to prevent power from being applied to the output cable when the cable is not connected to a load. There shall be no control or switch to activate the interlock for the 270; if the 270 VDC power supply is activated the interlock power supply shall also be activated. Upon application of the 270 VDC contactor close device the 28 VDC interlock shall provide the required 28 VDC signal to the load via pin “1” (commonly referred to as C) on the cable; following an interval of at least 100 milliseconds the 270 power supply shall activate and provide 270 VDC to the load. If at any time the 28 VDC signal is removed from pin “2” (commonly referred to as D) the 270 VDC contactor shall open, removing power from the aircraft and cable. The 28 VDC interlock output shall be designed to provide power to a baseline load of 0 to 200 microfarads of capacitance in parallel with any combination of resistive and constant power load. The 28 VDC interlock power supply shall be capable of providing a minimum of 15 amps continuous and up to 37.5 amps peak (for 250 milliseconds) with a minimum current demand rate of 60 amps per millisecond. The 28 VDC interlock output voltage shall be regulated to 28 VDC ± 1 VDC under the worst case combination of resistive or constant power load variations from no-load to full-load. The 28 VDC interlock output ripple amplitude shall be as defined in MIL-STD-704, Table IV. The 28 VDC distortion factor shall meet the requirements of MIL-STD-704 Table IV of 0.035 maximum and the distortion spectrum shall meet the requirements of MIL-STD-704 Figure 15. The 28 VDC interlock output shall remain within the range of 26 to 40 VDC under all load conditions during any defined 270 VDC loading conditions and under any fault current condition that occurs. The interlock voltage shall not drop below 26 VDC for more than 50 microseconds under any condition. The 28 VDC interlock output shall begin recovery from the voltage transient onset within the limits of MIL-STD-704 Figure 13 as modified herein by Figure 1A. The onset of voltage transient occurs when the output voltage, including voltage ripple, exceeds the limits of 28 +/1 VDC for a duration greater than or equal to 0.5 milliseconds or falls below 26 VDC for more than 50 microseconds. Note: the 270 VDC and the 28 VDC interlock returns are required to only be tied together on the aircraft side of the on-aircraft external power receptacle to avoid 270 VDC and 28 VDC load interconnection issues. Additionally, to support on-aircraft fault isolation, the 28 VDC interlock shall not be disrupted or removed during any 270 VDC load high current/time (di/dt) change (e.g. overload, over or under voltage, ripple, etc) and regulated voltage shall remain (this includes no voltage dropout below 26 volts for a duration longer than 50 microseconds). As further support for on-aircraft fault isolation, the 28 VDC interlock shall maintain power after the 270 VDC output power is removed from the aircraft so the on-aircraft protection devices can isolate the fault before the GPU contactor opens and before any fault condition is annunciated by the GPU. If required by the contractor’s design, the 28 VDC interlock power source may incorporate an ALDC function to compensate for line losses in the output cable. The 28 VDC interlock output shall also provide an I²t overcurrent protective function for the 16 AWG wire used to provide the interlock signal.

FIGURE 1A. Envelope of normal voltage transient for the 270 VDC 28 VDC interlock system.

3.4.2.2.9 Output start-up load. The 270 VDC power converter shall operate within the limits specified herein when 1,500 microfarads of capacitance in parallel with 0 to 54 kW of resistive power, constant power, or any combination thereof start-up loads are applied. The 270 VDC power supply shall be designed to preclude inadvertent trips for inrush currents during start-up loads not exceeding 2,000 amps with a 1.0 millisecond duration resulting from charging a capacitive load as high as 2,500 microfarads total. The 270 VDC power supply shall be designed to prevent nuisance tripping during start-up loads and transient conditions.

3.4.2.2.10 Output loads. The 270 VDC power supply shall operate within the limits specified herein when the following loads are applied:

a. Constant power load. 0 to 1,000 microfarads of capacitance in parallel with 0 to 72 kW of constant power load.

b. Baseline load. 2,500 microfarads of capacitance in parallel with the conditions listed in Table II below.

TABLE II. Baseline load conditions.

Condition #1 (0 to 100% CONSTANT Loads) Condition #2 (0 to 100 % RESISTIVE Loads)

0 to 72 kW ii

(i) 0 to 72 kW of constant power + 150% overload for 2 seconds (minimum), while meeting the minimum current demand rate of 200 amps/millisecond.

(ii) 0 to 72 kW of resistive load + 150% overload for 2 seconds (minimum), while meeting the minimum current demand rate of 200 amps/millisecond.

The integrated power package (IPP) is a bi-directional pulse wave modulated (PWM) power converter, which can operate as an active load or as a power source. See Figure 2, below.

FIGURE 2. External power source to IPP (single line diagram).

As an active load, the power bridge is a standard configuration 3 phase full-wave bridge inverter topology at a switching frequency of 20 kHz. As a power source, the power bridge functions as an active rectifier to condition the power output and its fundamental frequency is 1 kHz.

The time duration from when the IPP transitions from an active load to a power source is shown in Figures 9 and 10 can range from 1 second to 15 seconds.

c. Pulsed load 1. The converter shall support pulsed loads of up to 140 amps (peak to peak) over the frequency range of 50-500 Hz while maintaining ripple voltage within the limits of Table 2 herein, and distortion within the limits of Figure 3 below. The pulsed load has a duty cycle of 10% to 50%, indefinite duration, and the average current will not exceed 267 amps.

FIGURE 3. 270 VDC system distortion limits (Pulsed Load 1).

d. Pulsed load 2. The converter shall support pulsed loads of up to 70 amps (peak to peak) over the frequency range of 5,000-15,000 Hz while maintaining ripple voltage within the limits of Table 1 herein, and distortion within the limits of Figure 4, below. The pulsed load has a duty cycle of 50% with a duration of two minutes.

FIGURE 4. 270 VDC system distortion limits (Pulsed Load 2).

Note: The 50-500 Hz and 5,000-15,000 Hz pulsed loads will not occur simultaneously. The 50-500 Hz load will have a steady-state load of at least 22 kW during pulsing. The 5,000-15,000 Hz load will not have any additional steady-state load during the periods of pulsing.

e. Profile and transient loading (including start-up) profiles. For any surface activity (FLCS IBIT or stick stir) the max positive ramp rate is +5 kW/millisecond and the max negative ramp rate shall be -20 kW/millisecond.

FIGURE 5. FLCS IBIT (maximum steady-state baseload of 22 kW).

Note: Typical power profile for flight controls IBIT activity (maximum steady-state baseload of 22 kW). Two IBITs can be run in sequence with a 30 second dwell time between these events.

FIGURE 6. FLCS IBIT (minimum steady-state baseload of 3 kW).

Note: Typical power profile for flight controls IBIT activity (minimum steady-state baseload of 3 kW). Two IBITs can be run in sequence with a 30 second dwell time between these events.

FIGURE 7. FLCS Surface Maintenance Activity (maximum steady-state baseload of 22 kW).

Note: Typical power profile for flight controls surface maintenance activity (maximum steady-state baseload of 22 kW). This profile definition can be repeated for up to 30 minutes.

FIGURE 8. FLCS Surface Maintenance Activity (minimum steady-state baseload of 3 kW).

Note: Typical power profile for flight controls surface maintenance activity (minimum steady-state baseload of 3 kW). This profile definition can be repeated for up to 30 minutes.

FIGURE 9. IPP Start Activity (maximum steady-state baseload of 28 kW).

Note: Typical IPP start profile (maximum steady-state baseload of 28 kW). External power source may be paralleled with IPP for 250 milliseconds after starter cutoff.

FIGURE 10. IPP Start Activity (minimum steady-state baseload of 3 kW).

Note: Typical IPP start profile (maximum steady-state baseload of 3 kW). External power source may be paralleled with IPP for 250 milliseconds after starter cutoff.

FIGURE 11. FLCS IBIT with regen (minimum baseload of 3 kW).

Note: Typical power profile for flight controls IBIT activity (minimum steady-state baseload of 3 kW). Two IBITs can be run in sequence with a 30 second dwell time between these events.

FIGURE 12. FLCS IBIT with regen (maximum baseload of 28 kW).

Note: Typical power profile for flight controls IBIT activity (maximum steady-state baseload of 28 kW). Two IBITs can be run in sequence with a 30 second dwell time between these events.

FIGURE 13. FLCS Surface Maintenance Activity with regen (minimum baseload of 3 kW).

Note: Typical power profile for flight controls surface maintenance activity (minimum steady-state baseload of 3 kW). This profile definition can be repeated for up to 30 minutes.

FIGURE 14. FLCS Surface Maintenance Activity with regen (maximum baseload of 28 kW).

Note: Typical power profile for flight controls surface maintenance activity (maximum steady-state baseload of 28 kW). This profile definition can be repeated for up to 30 minutes.

3.4.2.2.11 Output load fault. Upon application of a hard short or a short between the aircraft cable, receptacle, or structure the GPU 270 VDC power supply shall limit output current. The GPU 270 VDC power supply shall support on-aircraft fault clearing. Semi-conductor type fuses shall not be utilized to provide 270 VDC power supply protection on the GPU.

a. F-22 fault support. The 270 VDC power supply shall be capable of surviving worst-case load current spikes (due to inrush or on-aircraft fault clearing) of up to 3,000 amps for 10 milliseconds without damage. Note that these are on-aircraft limits and the contractor shall limit short circuit current and duration on the GPU itself. The current waveform can be assumed to have an exponential decay from 3,000 amps for inrush and square for fault clearing.

b. F-35 fault support. To support on-aircraft fault isolation the 270 VDC power supply shall coordinate with the trip curve for a 120 amp contactor as shown in Figure 15 herein to ensure that the 120 amp contactor will “trip” prior to the 270 VDC power output fault condition (i.e. overcurrent or undervoltage). For clarification, the 120 amp contactor is on a separate leg of the aircraft circuit. The 270 VDC power supply shall operate in the envelope defined in Figure 16, herein, until an overload greater than 480 amps is detected. Upon a short between the aircraft receptacle and aircraft structure the 270 VDC power supply shall detect the short circuit and maintain current within 460-490 amps after 40 milliseconds regardless of the resistance in the current path for a minimum time duration so that the worst case fault duration, as defined by Figure 15 herein, is cleared by the aircraft 120 amp over current device (e.g. 480A for 2 seconds or 150 amps for 10 seconds). The 270 VDC power supply output voltage is allowed to fold back linearly at 300 amps and then collapse at 480 amps during the short circuit event; the 270 VDC power supply shall maintain a minimum of 260 VDC at 380 amps and a minimum of 220 VDC at 480 amps before voltage collapse at amperages exceeding 480 during the short circuit event (see Figure 16 herein). If the fault condition requiring greater than 300 amps clears in less than the time allowed in Figure 15, herein (I2t curve), the 270 VDC power supply shall recover within the regulated voltage levels defined Figure 1. The lower voltage limits of Figure 1 shall not apply during this event, but shall be in accordance with Figure 16, herein.

FIGURE 15. Trip coordination with a 120 amp on-aircraft contactor.

FIGURE 16. Fault coordination with the aircraft’s electrical power system.

3.5. Engine system The engine and related equipment shall be in accordance with Appendix B except as otherwise specified herein and shall be of the in-line 6 cylinder type design with a minimum displacement of 366 cubic inches (6.0 liters). The net power output rating of the engine, when continuously operated on JP-8 fuel at 5,000 feet elevation at 125 degrees Fahrenheit and determined in accordance with SAE J1349, shall be adequate for all performance requirements specified herein. The engine shall be equipped with anti-vibration systems and anti-vibration mounting points to minimize generator set vibration. Note: in certain applications the engine may spend extended amounts of time at both full load and part (low) load conditions. To reduce and minimize "wet-stacking" issues the engine fuel calibration shall be selected so that part load (10-20% of full load) conditions do not induce excessive amounts of fuel into the engine. Engine fuel consumption, horsepower, and torque curves shall be considered when selecting the operational speed of the engine and AC alternator combination to provide balance between required power, available power, and long-term durability.

3.5.1 Engine exhaust emissions. The engine shall be a diesel that is certified to comply with the Environmental Protection Agency (EPA) off-highway emission requirements at the time of contract award and design. The engine shall be certified by the manufacturer to operate on fuels listed herein and the engine shall meet all EPA exhaust emissions requirements while operating with EPA test fuel.

3.5.2 Engine starting. The engine of the GPU shall start at and above 0 degrees Fahrenheit with no external assistance. External starting assistance is allowed from -1 to -25 degrees Fahrenheit. The engine is required to operate, but not start at -26 to -40 degrees Fahrenheit. The engine shall start within 30 (± 10%) seconds for a + 32 degree Fahrenheit ambient condition. In colder ambient operating ranges of the GPU, the engine shall start with a maximum of three attempts, each attempt shall not exceed 30 (± 10%) seconds in duration (to avoid starter overheating and battery drain issues). Internal cyclic starting aids such as air intake heaters, glow plugs, etc. may be utilized at temperatures at or above 0 degrees Fahrenheit, or as required by engine manufacturer, with an indicator light on the control panel to denote activation.