10 STS Section J Attachment J.02 STS Specifications.pdf

DEPARTMENT OF TRANSPORTATION

STATIC TRANSFER SWITCHES EQUIPMENT SPECIFICATION

PERFORMANCE GOALS

OPERATING CHARACTERISTICS

February 2025

SECTION-J, ATTACHMENT J.1 STATIC TRANSFER SWITCHES (STS) EQUIPMENT

SPECIFICATION

1.0 GENERAL

1.1 Summary

These specifications describe the electrical and mechanical requirements for Static Transfer Switches (STS). The specified unit must be designed, manufactured, and tested to this specification. The specified unit must include all operation, annunciation, detection, and switching characteristics specified in this document. The STS units must be designed to provide operational and annunciation characteristics as specified in this document.

1.2 Standards

Contractors are required to be in compliance with the latest version of Specifications, Standards and Publications. The STS units must be designed, manufactured, tested, and installed in compliance with the latest versions of the following standards:

a. Safety: Underwriters Laboratories (UL), 1008, 1778,

b. Electrical:

1. National Electrical Manufacturers Association (NEMA) ICS 10

2. IEEE Std C62.41.3-2020

3. FAA-G-2100H

4. NEC Code 2023

5. FAA-STD-019f Chg.3 and FAA-STD-20B, FAA-C-1217H Chg 2, & FAA-STD-032

c. Software: ANSI, IEEE

d. EMC: FCC part 15 class B

1.3 Environment Requirements

1.3.1 Storage Temperature

Storage Temperature range must be -40°C to+ 70°C.

1.3.2 Operating Temperature

Operating temperature range must be 0°C to 40°C (32°F to 104°F) for cabinet operation and 0° to 45°C (32° to 113°F) for panel operation.

1.3.3 Relative Humidity

Operation must be reliable in an environment with 0% to 95% non-condensing relative humidity.

1.3.4 Operating Altitude

The unit must be capable of operation in altitudes up to 3,000 feet above sea level.

1.3.5 Audible Noise

The unit must not generate audible noise greater than 55 dB outside a radius of 6 feet from the unit during normal operation and while no alarms are being annunciated by the unit.

1.3.6 Magnetic Fields

No appreciable magnetic fields must be generated. Unit must be capable of being use directly in computer rooms in any location without danger to data storage systems or devices.

1.3.7 Seismic

The STS units must be rated for installation in a Seismic Zone 4. Seismic Zone 4 classification is the least dangerous and has the lowest probability in causing damage out of all the seismic zones.

1.3.8 Radio Frequency (RF) Field

The Static Switch must be protected for RF fields that could cause any interference with the performance of the switch regardless if the configuration has either no panels or its doors are open/removed.

2.0 PRODUCT

2.1 General Requirements for all Static Transfer Switches (STS)

2.1.1 Switch Logic Operation

2.1.1.1 Input Selection

The static switch must allow the selection of either source 1 or source 2 as the preferred source.

The switch must always default to the preferred source when it is desirable in accordance with Information Technology Industry (ITI) - Computer and Business Equipment Manufacturers Association (CBEMA). The alternate source will be selected if the preferred source is undesirable or unusable and the alternate source is desirable. When both sources are desirable, the preferred source is always selected. The auto-retransfer to the preferred source also needs to be able to be deactivated in settings in case the use case doesn’t want to retransfer back to the preferred source after transfer.

2.1.1.2 Voltage Sensing

The specified unit must detect undervoltage and overvoltage conditions, maintain the connection between a viable voltage source and the critical load, and if necessary, transfer to the alternative power source. Each of these conditions set-points must be define the voltage level and timing set points. The set points must be adjustable to insure that all critical loads are operated within the safe voltage regions graphically depicted by the ITI (CBEMA) curve.

This is the accepted industry standard for American made power supplies for computerized equipment and is the accepted guideline for FAA equipment in accordance with FAA standards and orders. The instantaneous rate of change of voltage as a function of time (dv/dt) / (t) as described by the ITI (CBEMA) curve must be utilized as the testing criteria for fast and slow changing voltage detection.

2.1.1.3 Transfer Time

The specified unit must detect ITI (CBEMA) defined undervoltage and overvoltage conditions and transfer to an available and desirable source within the allowable region of operation as defined by the ITl (CBEMA) curve. The specified device must respond in a time period described as follows. The time period must be a period of time such that the detection time plus the transfer time must be less than the safe boundary time of the ITI (CBEMA) curve. The safe boundary time of the ITI (CBEMA) curve is all points on the ITI (CBEMA) curve defining the maximum time versus voltage boundary for all acceptable regions of operation below 3 seconds. The total transfer time for the static switch, including fault sensing and transition to a desirable source must be less than 1/4 cycle (4.175 millisecond) for the loss of selected source.

2.1.1.4 Current Sensing

The specified unit must detect overcurrent (phase faults), shorted and open static switch conditions on all 3 phases and neutral for both source 1 and source 2 switches.

2.1.1.5 Handling of Fault Conditions

The specified unit must not transfer a detected overload to another source. The static switch must be able to detect overcurrent, determine that it is a load fault, and stay on the same source until the fault is cleared by properly coordinated devices downstream of the static switch.

2.1.1.6 Phase and Neutral Transfer Requirements

The specified unit must transfer 3 phases and the neutral from one source to the three phases and the neutral of the other source for the critical loads. Neutral switching is only required for 4-pole switches, The specified unit must switch in the following order: 1) failed phases off, 2 ) new phases on. The switch must be transfer-tested to verify a spike or drop level considered a transient and transient and solid state components must not induce a transient on the phase and neutral lines.

2.1.1.7 Measurement, Decision, and Action Circuitry

The specified unit must utilize noise immune, direct measurement operational amplifiers, as well as and digital logic switching for both the decision making and transfer command process.

Fetch and execute routines may not be utilized to gather, store, or compare real time voltage and current data or to transfer critical information (that could be flawed by noise induced even bit errors) while the switch is operationally protecting the critical loads. Fetch/Execute operations are not acceptable in the decision making process to transfer and are not acceptable in the initiation of the transfer process. An example of Fetch/Execute operations is a meter installed within the switch, and communication over Ethernet to get voltage and current levels.

The switch makes logic determinations based on said values. The logic must be designed to make direct measurements of voltage and current values from all sources and make direct comparisons of all critical parameters against pre-adjusted and calculated ITI or CBEMA curve acceptable set-points. The comparison technique of the measured variable verses the set point may be digital, analog, or a combination of digital and analog logic. The comparison technique must not require a fetch execute routine to load the value of the measured variable or to load the value of the set point.

2.1.1.8 Set Point Accessibility

All voltage, current, and timing set-point adjustments must not be accessible from the operator's panel of the static switch. The key switch must enable only front panel controls and must not enable adjustment of any operational set-point for either detection or transfer functions. The set-point adjustments must only be accessible by a plug-in enabling device that can be removed from the switch during normal operation or via a password protected menu screen. The plug-in device must require the entry of a password to gain access to the static switch set-point adjustments.

2.1.1.9 Adjustments

The specified unit must incorporate the following adjustments. Refer to 2.1.1.8, above, to determine the accessibility requirements to perform the adjustments for the static switch.

2.1.1.9.1 Phase Angle Difference

This adjustment must allow the switch to transfer over a range of zero to 35 degrees of the sine wave phase difference between the preferred and the alternate sources. It must be adjusted to allow a transfer between zero and 15 degree's phase displacement.

2.1.1.9.2 Overvoltage

This adjustment must allow the switch to detect and transfer on an overvoltage threshold that is adjustable from 105% to 120% of the nominal line voltage. It must be adjusted to 110% of the nominal line voltage.

2.1.1.9.3 Undervoltage (Below the Desired Value)

This adjustment must allow the switch to detect the first level of undervoltage over a window ranging from -5% to -25% of the nominal voltage. For a 208 volt switch this window ranges from 114/198 volts down to 90/156 volts. The setting must be adjusted to 108/187 volt's AC rms. For a 277/480 volt switch, this window ranges from 264/456 volts down to 208/360 volts.

The setting must be adjusted to 250/432 volts rms.

2.1.1.9.4 Undervoltage (Below the Usable Value)

This adjustment must allow the switch to detect the second level of undervoltage over a window ranging from -20% to -32% of the nominal range. For a 120/208 volt switch this window ranges from 96/167 volts down to 82/142 volts. The setting must be adjusted to 84/146 volts rms. For a 277/480 volt switch, this window ranges from 222/384 volts down to 189/327 volts. The setting must be adjusted to 159/336 volts rms.

2.1.1.9.5 Overload for Source

This adjustment must allow the switch to detect and annunciate an overload condition for the switch over a window that encompasses 100-125% of the nominal amperage. The detection range may extend beyond this window as long as the 100%-125% window is covered. The adjustment may be made by factory personnel or technicians and does not need to be user adjustable. For a 150 amp switch it must be adjustable over the range of 150 amps to 188 amps load current. The setting must be adjusted to 173 amps rms current. For a 250 amp switch it must be adjustable over the range of 250 amps to 313 amps load current. The setting must be adjusted to 288 amps rms current.

For a 400 amp switch it must be adjustable over the range of 400 amps to 500 amps load current.

The setting must be adjusted to 460 amps rms current. For a 600 amp switch it must be adjustable over the range of 600 amps to 750 amps load current. The setting must be adjusted to 690 amps rms current.

2.1.1.9.6 Overload (Failed/Shorted Load)

This adjustment must allow the switch to detect a load fault and inhibit the transfer until the fault clears over a window from 150%-275% or greater of nominal amperage. The adjustment may be user-adjustable but must be at minimum factory/vendor adjustable. For a 150 amp switch it must be adjustable over the range of 225 amps to 413 amps load current or greater.

The setting must be adjusted to the normal load current of 150 plus 380 amps for a total of 530 amps. For a 250 amp switch it must be adjustable over the range of 375 amps to 688 amps load current or greater. The setting must be adjusted to the normal load current of 250 plus 633 amps for a total of 883 amps. For a 400 amp switch it must be adjustable over the range of 600 amps to 1100 amps load current or greater. The setting must be adjusted to the normal load current of 400 plus 1012 amps for a total of 1412 amps. For a 600 amp switch it must be adjustable over the range of 900 amps to 1650 amps load current or greater. The setting must be adjusted to the normal load current of 600 amps plus 1518 amps for a total of 2118 amps.

2.1.1.9.7 Frequency Detection

This must be fixed over a window of 57 to 63 Hertz in accordance with the input frequency allowable. This could be present when on engine generators (EG) and on bypass operation.

2.1.1.9.8 Re-Transfer Time

This adjustment must allow the switch to delay re-transfer to the preferred source until the source has had sufficient time to settle. It must allow the facility to stagger static switch load re-transfer times. It must have an adjustment range between 0 to 3600 seconds. It must be set to stagger the load re-transfers at 15 second intervals.

2.1.1.9.9 Reserved

2.1.2 Controls

The specified unit must have the following controls:

2.1.2.1 Lamp Test

This control must be designed to illuminate all indicator LED's and/or lamps. This control must operate all segments of all dual color indicators used to observe functional status. This is not required if the STS does not have any indicator LEDs or Lamps.

2.1.2.2 Reset Fault Control

This control must be designed to reset latched overloads that have latched the switch onto the original source to clear downstream faults.

2.1.2.3 Source Selector for Source 1

This control must be designed to select Source 1 as the preferred source for the critical loads.

2.1.2.4 Source Selector for Source 2

This control must be designed to select Source 2 as the preferred source for the critical loads.

2.1.2.5 Auto Retransfer Selector

This control must be designed to allow the operator the option of selecting automatic retransfer when the preferred source is normal or to prevent automatic retransfer and remain on the alternate source any time a transfer takes place and the alternate source remains normal.

2.1.2.6 Control Enable Key Switch

The specified unit must have a safe-guard (in the form of a key and/or password) designed to lock out all control functions except lamp test. Only when the switch is securely enabled, may one perform source select functions, retransfer mode selection, and alarm clear/reset functions.

2.1.2.7 Reset (Main or Master)

This reset functional control must be located away from the normal access of the front panel but located internally in the switch. It must provide a power on type of reset and an all-alarm reset able to maintain its load on current source when said switch is selected.

2.1.2.8 Alarm Silence Switch

This switch must silence the audible alarm but must not reset any alarm or indication.

2.1.3 Indicators

2.1.3.1 Indicator Functions

2.1.3.1.1 Switch not OK (Red Indicator Prominent in the Display Area) This indicator must illuminate when any alarm is detected.

2.1.3.1.2 Availability of Source 1 Input

This indicator must clearly convey and delineate the conditions of Source 1 as follows: 1) Good, 2) Not Desirable, or 3) Not Useable. This indicator must noticeably indicate that the switch will not transfer to this source due to a logic inhibit such as an overload on the power source being utilized at this moment.

2.1.3.1.3 Availability of Source 2 Input

This indicator must clearly convey and delineate the conditions of Source 2 as follows: 1) Good,

2) Not Desirable, or 3) Not Useable. This indicator must noticeably indicate that the switch will not transfer to this source due to a logic inhibit such as an overload on the power source being utilized at this moment.

2.1.3.1.4 Load on Source 1

This indicator must indicate that Source 1 is supplying load power.

2.1.3.1.5 Load on Source 2

This indicator must indicate that Source 2 is supplying load power.

2.1.3.1.6 Source 1 is Preferred

This indicator must indicate that Source 1 has been selected as the preferred source and the system will default to this source while in normal operation and the switch is allowed to retransfer.

2.1.3.1.7 Source 2 is Preferred

This indicator must indicate that Source 2 has been selected as the preferred source and the system will default to this source while in normal operation and the switch is allowed to retransfer.

2.1.3.1.8 Retransfer Enabled Indicator

This indicator must indicate that the automatic retransfer mode has been selected and the switch will return to the preferred source automatically.

2.1.3.1.9 Retransfer Enabled Off Indicator

This indicator must indicate that the automatic retransfer mode has been deselected and the switch will remain on the alternate source until manually transferred.

2.1.3.1.10 Critical Load Powered Up

This indicator must indicate that either Source 1 or Source 2 static switch is available to provide a path for the power to reach the critical load.

2.1.3.2 Indicator Conditional Response

Indicators must indicate either individually or in combination each of the following conditions:

2.1.3.2.1 Source Annunciated

The indicator must be able to indicate the usability of one Source catalogued in an alarm log that acutely describes each complication not limited to frequency levels, voltage use (under or over), shorted devices (SCR or IGBT, etc.), an open breaker, and the ability to transfer responsibilities to a second Source’s available devices.

2.1.3.2.2 System Conditions Annunciated

The indicators must indicate an over Temperature condition of any device (SCR or IGBT, etc.), the logic cabinet, indicate when any fan fails, and indicate when an external transfer inhibit command is active while on either source and when either Source 1 or Source 2 is on bypass.

2.1.4 Communications

The static switch must offer Aux and Shunt-trip communication options. The Static Switch with communication must utilize the protocol/protocols Modbus RTU or Modbus TCP/IP. The Static Switch with communication must utilize the protocol/protocols Modbus RTU or Modbus TCP/IP.

2.1.4.1 Modbus RTU

The Static Switch equipped with Modbus RTU must communicate over RS485. Modbus over RS232 alone is prohibited. Modbus RTU connector must be via of a serial port, terminal block, RJ11, or RJ54 port. The Modbus RTU configuration must be configurable from the Static Switch screen, if no screen is available the setup can be adjusted via the serial port utilizing a password-protected, personal, computer-based program in order to communicate with the static switch. If configuration software is required, it must be provided with the Static Switch.

2.1.4.2 Modbus TCP/IP.

If the Static Switch utilizes Modbus TCP/IP the configuration must be configurable via device screen, if the device doesn’t have a display the configurations must be able to be configured over serial communication.

2.1.4.3 Auxiliary Contacts

The static switch must provide Auxiliary contacts to allow field wiring to monitor the switch status. The static switch must annunciate the following contacts:

a. Breakers open/close statuses

b. Breakers trip statuses

c. Source Selection

d. Alarm Status

2.1.4.4 Time

The Static Switch must be designed to sync the switches internal clock to a central clock. If the switch utilizes Ethernet the selection of time synchronizing protocol can be either Network Time Protocol (NTP) or Precision Time Protocol (PTP). If the device doesn’t utilize Ethernet the serial interface Inter-Range Instrumentation Group Format B (IRIG-B) protocol is an acceptable protocol.

2.1.4.5 Shunt Trip Capability

The Static Switch must be designed to provide shunt trip capability for both Source 1 and Source 2 input circuit breakers. The shunt trip circuit must activate under either of the following conditions:

a. A shorted (SCR or IGBT, etc.,) device on one source must shunt trip the other source input breaker.

b. A shorted (SCR or IGBT, etc.,) on an unusable source.

In lieu of shunt trip capability, the STS must use other means to inhibit transfer to sources as described in conditions a and b above.

2.1.5 Cooling Requirements

2.1.5.1 Cooling Media

Static Transfer Switch cooling is by ambient air using mechanical means or convection.

2.1.5.2 Fans

All fans used must be manufactured using ball bearing and include failure indicators able to produce a summarized log of each notifications. The Rated fan life must be a minimum of 40,000 hours

2.1.5.3 Filters

All filters must be accessible from the front panel and must be replaceable without shutting down the switch. Filters must meet Federal Specification A-A-1419 or MIL-F-16552F if velocity exceeds 300 FPM. Standard manufacturer filters are acceptable only if the manufacturer provides filters designed to work with the switch and supplies specifications for these filters. A "filter-less" option is allowed. If no filters are used, the manufacturer must specify the environmental restrictions applicable to the system.

2.1.5.4 Over Temperature Detection

The static switch must have over temperature detection in each device (SCR or IGBT, etc.,) heat sink to protect all phase switching devices and all neutral switching devices.

2.1.5.5 Convection Cooling

Passive cooling is acceptable if all cooling requirements are meet by free flow of ambient air, without the aid of mechanical means, as permitted by the enclosure design.

2.1.6 Additional Required Features

2.1.6.1 Redundant Logic Power Supplies

The switch must have redundant logic power supplies; each powered independently by either source 1 or source 2. The power supplies must be configured with component isolation so that either supply can operate the logic and device (SCR or IGBT, etc.,) drive circuits as a standalone supply and can take over the task without interruption if the other source or source power supply fails. Either failed supply must be annunciated in the alarm circuitry. In the case of a large overvoltage condition on the switch’s inputs, the power supply must not adversely affect the logic power and switch to the alternative power supply without a loss logic power.

In the case of a dual power logic failure, the Static Switch must remain on the current source without dropping the load.

2.1.6.2 Power Failure Log

A log that can be computer accessed through the serial/Ethernet port must record all outages, transfer operations, and any switch alarm including date and time of the event. The switch must maintain the power failure log in a nonvolatile memory (preferred) or by rechargeable battery backup for a minimum of seven (7) days without power.

2.1.6.3 SCR Characteristics

Device (SCR or IGBT, etc.,) data must be used to enhance the transfer process through gate timing. The manufacturer must use the device "off" curves to determine the time that the charge is stored on the gated off device to time the gating process; thereby minimizing the possibility of shoot-through. The manufacturer must utilize Devices with charge (Q) discharge characteristic time such that the sum of the discharge time plus the gating on time must be less than 500 microseconds.

2.1.6.4 Positive Logic Indicators

All LED and lighting indicators must illuminate when the condition annunciated is true. The manufacturer must not utilize negative logic to circumvent any required annunciation requirement in this specification.

2.1.6.5 Accessible and Ample Test Points

All circuit boards must be fully illustrated in the manufacturer's service manual and all function's annunciated must have board accessible test points and indicators for comprehensive static switch troubleshooting.

2.2 Static Transfer Switch Electrical And Physical Requirements The Static Transfer Switch (STS) has a requirement for 208 volt and 480 volt switches in amperages of 150, 250, 400 and 600 Amps. The 208 volt STS are needed in two distinctly different physical configurations and option of 3 or 4-Pole switching.

2.2.3 Static Transfer Switch (STS), 208 Volt, 3-pole/4-pole, 150 Amp, 250 Amp, 400 Amp, 600 Amp, with Bypass Cabinet, Free Standing

2.2.3.1 Free Standing Cabinet Physical Requirements

2.2.3.1.1 Static Transfer Switch with Integral Bypass Cabinet The STS cabinet must be free standing with capability of mounting the cabinet back against a wall. The entire enclosure housing the STS, manual bypass, and display screen maximum dimensions are:

Height: 91 inches

Width: 34inches

Depth: 34-inches.

2.2.3.1.2 Mechanical Configuration Requirements

2.2.3.1.2.1 Service Access

Service Access must be from the front primarily. This will permit installation of the STS enclosure with back panel against a wall. Service access for the STS enclosure may be available from the side or the rear of the enclosure provided that, in addition to front access, ONLY single side access OR rear access is needed to properly maintain the unit.

2.2.3.1.2.2 Cable Entry

Cable entry must be allowed from the top and/or bottom, as designated at the time of order. The vendor must clearly designate the chosen entry point, such as in the part number.

2.2.3.1.2.3 Cooling

See paragraph 2.1.5 above.

2.2.3.1.2.4 Mean-Time-to-Repair

The design must be such that the switch can be restored to basic continuity of service within 30 minutes or less by trained FAA technical personnel.

2.2.3.2 Electrical Requirements

2.2.3.2.1 Inputs

2.2.3.2.1.1 Input Voltage

The nominal input voltage must be three phase 120/208 volt's ac ± 10%.

2.2.3.2.1.2 Input Voltage Operating Range

The 120/208 volt unit must be able to operate normally utilizing the input voltage over a range of 82/142 to 144/250 volt's ac rms. The unit must continue operation (gating SCRs) with an overvoltage transient of 140% (168/291 volt) on one or both of its sources without interruption to load. It may change sources if the other source is more favorable based on setpoints.

2.2.3.2.1.3 Input Voltage Connection

The input voltage must be connected three phase and four wire.

2.2.3.2.1.4 Neutral Plate Connection

The input neutral must be manufactured with a continuous rated ampacity of 100 percent of line current.

2.2.3.2.1.5 Frequency

The unit must be designed to operate normally over a frequency range of 57 to 63 Hertz.

2.2.3.2.1.6 Input Conductor Ratings

Phase conductors and neutral must be provided with a wire size of at least 125% of the STS amp rating for the switch with a minimum of 600 volt route mean square rms) ac voltage rating.

All bus work and interconnecting cables must be made of copper. Aluminum is not acceptable (except for the semiconductor heat sinks).

2.2.3.2.2 Outputs

2.2.3.2.2.1 Output Voltage

The output voltage must be no more than 4 volts rms. below the selected source.

2.2.3.2.2.2 Output Current

The output current rating must be no less than STS amps rms continuous.

2.2.3.2.2.3 Overload Capacity

The device must be capable of providing overload current to the load under the following conditions:

125 % of rated load capacity for 5 minutes

300 % of rated load capacity for 20 seconds 330 % of rated load capacity for 15 seconds 360 % of rated load capacity for 10 seconds

2.2.3.2.2.4 Inrush

The device must be capable of withstanding 1200% current for 8.33 milliseconds.

2.2.3.2.2.5 Fault Clearing

The device must be capable of withstanding 22,000 amps symmetrical fault current.

2.2.3.2.2.6 Voltage Withstand

The device must be capable of withstanding 2000 volt transients as specified by ANSI C62.41B.

2.2.3.2.2.7 Output Conductor Ratings

amp rating for the switch with a minimum of 600 volt rms. AC voltage rating. All bus work and interconnecting cables must be made of copper. Aluminum is not acceptable (except for the semiconductor heat sinks).

2.2.3.2.2.8 Performance

The unit must perform at 98% efficiency. Defined as ratio of output power to input power.

2.2.4 Static Transfer Switch (STS), 480 Volt, 3-pole/4-pole, 150 Amp, 250 Amp, 400 Amp, 600 Amp, with Bypass Cabinet, Freestanding.

2.2.4.1 Free Standing Cabinet Physical Requirements

2.2.4.1.1 Static Transfer Switch with Integral Bypass Cabinet The STS cabinet must be free standing with capability of mounting the cabinet back against a wall. The entire enclosure housing the STS, manual bypass, and display screen maximum dimensions are:

Height: 91 inches

Width: 34inches

Depth 34-inches

2.2.4.1.2 Mechanical Configuration Requirements

2.2.4.1.2.1 Service Access

Service Access must be from the front primarily. This will permit installation of the STS enclosure with back panel against a wall. Service access for the STS enclosure may be available from the sides or rear of the enclosure provided that, in addition to front access, ONLY single side access OR rear access is needed to properly maintain the unit.

2.2.4.1.2.2 Cable Entry

Cable entry must be allowed from the top and/or bottom, as designated at the time of order. The vendor must clearly designate the chosen entry point, such as in the part number.

2.2.4.1.2.3 Cooling

See paragraph 2.1.5 above.

2.2.4.1.2.4 Mean-Time-to-Repair

The design must be such that the switch can be restored to basic continuity of service within30 minutes or less by trained FAA technical personnel.

2.2.4.2 Electrical Requirements

2.2.4.2.1 Inputs

2.2.4.2.1.1 Input Voltage

The nominal input voltage must be three phase, 480 volt ac ± 10%.

2.2.4.2.1.2 Input Voltage Operating Range

The 277/480 volt unit must be able to operate normally utilizing the input voltage over a range of 189/327 to 333/576 volt's ac rms. The unit must continue operation (gating SCRs) with an overvoltage transient of 140% (387.8/672 volt) on one or both of its sources without interruption to load. It may change sources if the other source is more favorable based on setpoints.

2.2.4.2.1.3 Input Voltage Connection

The input voltage must be connected three phase and four wire.

2.2.4.2.1.4 Neutral Plate Connection

The input neutral must be manufactured with a continuous rated ampacity of 100 percent of line current.

2.2.4.2.1.5 Frequency

The unit must be designed to operate normally over a frequency range of 57 to 63 Hertz.

2.2.4.2.1.6 Input Conductor Ratings

amp rating for the switch with a minimum of 600 volt route mean square rms) ac voltage rating.

2.2.4.2.2 Outputs

2.2.4.2.2.1 Output Voltage

The output voltage must be no more than 4 volts rms below the selected source.

2.2.4.2.2.2 Output Current

The output current rating must be no less than STS amps rms continuous.

2.2.4.2.2.3 Overload Capacity

The device must be capable of providing overload current to the load under the following conditions:

125 % of rated load capacity for 5 minutes 300 % of rated load capacity for 20 seconds 330 % of rated load capacity for 15 seconds 360 % of rated load capacity for 10 seconds

2.2.4.2.2.4 Inrush

The device must be capable of withstanding 1200% current for 8.33 milliseconds.

2.2.4.2.2.5 Fault Clearing

The device must be capable of withstanding 22,000 amps symmetrical fault current.

2.2.4.2.2.6 Voltage Withstand

The device must be capable of withstanding 2000 volt transients as specified by ANSI C 62.41B.

2.2.4.2.2.7 Output Conductor Ratings

amp rating for the switch with a minimum of 600 volt rms. AC voltage rating. All bus work and interconnecting cables must be made of copper. Aluminum is not acceptable (except for the semiconductor heat sinks).

2.2.4.2.2.8 Performance

The unit must perform at 98% efficiency. Defined as ratio of output power to input power.

3.0 TESTING

3.1 Quality Assurance

The specified unit must be factory quality assurance tested. After a 24 hour burn-in, all switch detection functions, transfer functions, interlock functions and all annunciations must be verified operational. The static switch must be signed off by a manufacturer's quality assurance officer. The sign off document must be affixed to the switch stating the full name of the quality assurance officer, the date and time the sign off occurred.