Frequency Converter UPS:

Series UPSC Guideform Specification


1.1 Summary:
This specification describes a three phase static uninterruptible power supply frequency converter, with the required battery backup to support the load when there is a loss of utility.  The following specification is intended to provide specifications for products with the quality and performance characteristics required for a static solid-state uninterruptible power supply system with built in frequency conversion. The static uninterruptible power supply frequency converter, hereafter, shall be referred to as the “UPSC”.

1.2 Furnished with Equipment:

  • Factory Test Report
  • Protective Packaging
  • Installation Drawings
  • OEM O&M Manual
  • Warranty Statement
1.3 Documents & Standards:
  • National Electrical Code, NFPA 70-2005.
  • IEEE C2 (1993) National Electrical Safety Code.
  • IEEE C62.41 (1980) Guide for Surge Voltage in Low-Voltage AC Power Circuits.
  • FS W-C-375 (Rev. B; Notice 1) Circuit Breakers, Molded Cases, Branch Circuit and Service.
  • NEMA AB 1 (1986; Rev. 1989) Molded Case Circuit Breakers and Molded Case Switches.
  • NEMA 250 (1985; Rev. 1988) Enclosures for Electrical Equipment (1000 Volts Maximum).
  • Occupational Safety & Health Act (OSHA).
  • Local Codes & Authorities having jurisdiction for this installation.
1.4 System Description:

The UPSC shall automatically provide continuous, regulated AC power to critical loads under normal and abnormal conditions, including loss of input AC power. The UPSC module rectifier/charger shall convert the incoming AC input power to DC power for the inverter and for charging the batteries. The inverter shall supply AC power continuously. Inverter output shall be at the programmed frequency and voltage, and shall supply clean AC power to critical loads. The battery shall bridge the gap in a loss of utility power.

The UPSC module shall consist of a solid state SCR rectifier/battery charger, a solid state PWM inverter, external battery cabinet, protective fuses, protective devices, and accessories as specified here that shall automatically effect continuity of electric power within specified tolerance without interruption – upon failure or deterioration of the normal AC power source. Continuity of electric power to the load shall be maintained for an emergency period with the inverter supplied by the battery, up to the specified protection time or until restoration of the normal input AC power.

The UPSC shall be a standard product of the manufacturer and shall be the manufacturer’s latest design that complies with the specification requirements hereafter. The unit shall have a calculated mean time between failure (MTBF) exceeding 24,000 hours as calculated when the UPSC is provided with yearly factory authorized service and maintenance.

The UPSC shall be a single system rated to supply the full load as specified herein. A (N+X) paralleled UPSC system shall be utilized for accomplishing redundancy, or for building power as required for the application. A redundant UPSC system shall have each module rated to supply full load as specified. A paralleled UPSC system intended for building power shall be rated as specified by the requirement.

1.5 System Operation:

1.5.1 Normal:
AC line power shall be supplied continuously to the UPSC. The system’s output shall be connected to the critical load within the specified voltage and frequency range in order to provide clean, regulated AC power.

1.5.2 Input Power Disturbance:
With a loss of normal input power, the battery shall supply DC power to the inverter so that there is no interruption of AC power to the critical load whenever the AC input power sources deviate from the specified tolerances or fail completely.

Normal Operation Resumed: When input power is re-encountered the UPSC will transition from the DC being supplied to the inverter from the emergency batteries to the DC being supplied by the rectifier. The process will be automatic and shall cause no interruption to the power being supplied to the critical load downstream of the UPSC.

1.6 Quality Assurance:

The manufacturer shall have a Quality Assurance program in place with inspection of incoming parts, modular assemblies, and final products. The manufacturer shall have a designated QA manager who is responsible for overseeing the overall QA process, as well as, Quality Control representatives responsible for actively overseeing the manufacturing process.

A final test procedure for the product shall include a check of all performance specifications and a minimum “burn in” period. An on-site test procedure shall include a check of controls and indicators after installation of the equipment.

Storage, Handling, & Delivery: The equipment  shall be shipped on a wooden pallet suitable for forklift handling. The equipment shall be covered with plastic sheeting to prevent dust and dirt from entering the unit during shipment. For international shipment, the wooden pallet will be constructed of treated wood and shall meet all other specifications required for international freight.

1.7 Submittals:

1.7.1 Proposal:
Catalog cut sheets and/or data sheets describing the proposed equipment shall be submitted with the proposal. A users listing shall be available upon request giving company names, locations, and systems installed. All deviations from this specification shall be listed and included with the proposal.

1.7.2 Receipt of Order:
A minimum of two sets of installation drawings showing outline dimensions, weights, connections, and a one-line diagram of the UPSC shall be sent to the purchaser to be used in planning the installation of the system.

1.7.3 Formal Approval:
If a formal submittal approval is required for the project then the following should be requested, submitted, and approved before design/construction of the UPSC commences:
  • Equipment Installation Outline
  • External Cabling Connection Diagram
  • Equipment One-Line Power Diagram
  • Equipment Elevation Drawing
  • “Other” Site Evaluation Diagrams
1.7.4 Delivery of Equipment:
As a minimum, the following shall be provided with the equipment upon its arrival to the final destination:
  • Operation & Maintenance Manual
  • System Installation Procedures
  • System Operation Procedures
  • System Troubleshooting Instructions
  • System Maintenance Requirements
  • Recommended Spare Parts List
  • Final Test Report Copy
1.8 Warranty:
The manufacturer shall state his warranty of the equipment, and in no case shall it be less than 12 months after start-up or 18 months after shipment, whichever occurs first. A warranty statement will be provided with the equipment and included as part of the overall O&M manual.


2.1 System Capacity:

The UPSC system capacity will be rated for applications ranging from 10kVA to 2,000kVA.

2.2 UPSC Input:

2.2.1 Input Voltage/Frequency:
208, 440, 460, 480, or 600 Volts at 60Hz, and 208, 380, 400, 415, or 600 Volts at 50Hz. These three phase input voltages are available in 3-wire (DELTA) or 4-wire (WYE) configurations.

2.2.2 Voltage Operating Tolerance:
+15% to -20% of Nominal.

2.2.3 Power Walk-In:
0% to 100% over 20 seconds, but capable of handling 100% step load.

2.2.4 Input Current Distortion:
For UPSC units 120kVA and greater the maximum current distortion is 15% THD at nominal input voltage while providing full rated output power. For UPSC units 80kVA and below the maximum current distortion is 33% THD at nominal input voltage while providing full rated output power.

Starting Inrush: When the UPSC is turned on and after the first half cycle, the inrush current shall not exceed 100% of the rated full load current. A “soft start” power walk-in circuit shall be used so that the rectifier ramps up to full load.

2.2.6 Power Factor:
Between 0.8 and unity of steady state line and load variations from half load to full load as specified herein.

2.2.7 Electromagnetic Interference (EMI):
Provide units that are tested and meet FCC Class A regulations for radiated emissions.

2.2.8 Neutral Currents:
Shall not exceed 2% of any individual phase current at no load and at full load.

2.3 UPSC Output:

2.3.1 Output Voltage/Frequency:
208, 440, 460, 480, or 600 Volts at 60Hz, and 208, 380, 400, 415, or 600 Volts at 50Hz, and 200/115 and 208/120 Volts at 400Hz. These three phase output voltages are available in 3-wire (DELTA) or 4-wire (WYE) configurations. The phase rotation of the output voltage shall be clockwise sequence of A-B-C.

2.3.2 Voltage Regulation:
1% Steady State.

2.3.3 Voltage Adjustment:
+/- 10% of Nominal.

2.3.4 Frequency:
50Hz or 60Hz plus or minus 0.1Hz maximum free running. 400Hz plus or minus 0.4Hz maximum free running.

2.3.5 Frequency Stability:
Output frequency within plus or minus .1 Herts for all operating conditions, including maximum and minimum specified input voltages, ambient temperature, and relative humidity. The frequency regulation shall be independent of load changes.

2.3.6 Efficiency:
The UPSC shall have a minimum efficiency of 91% at nominal voltage and full load.

2.3.7 Power Factor:
Output power rating shall be 0.8 power factor lagging.

2.3.8 Load Range:
Operate into a non-linear load with a maximum crest factor for each phase current of 2.0. The crest factor is the ratio of the peak value to the RMS value under steady state conditions. The applied peak load current shall not exceed the maximum peak rated current of the UPSC. The maximum peak rated current is defined as the full load RMS current times 1.414.

2.3.9 No Load Input Losses:
 The UPSC shall have no-load input losses no greater than 10% of the output kVA power rating at nominal input voltages.

2.3.10 Phase Angle Regulation:
Displacement angle between adjacent voltage phases shall be 120° plus or minus 2° with a balanced load and plus or minus 4° with three phases for 15% unbalanced load. A 15% unbalanced load is defined as:
  • Phase A at full rated single phase load.
  • Phase B at 85% of Phase A.
  • Phase C at 85% of Phase A.
2.3.11 Output THD:
For a balanced linear load the THD is not to exceed 3% line-to-line. Maximum single harmonic distortion is not to exceed 2% of the fundamental at the nominal voltage.

2.3.12 Amplitude Modulation:
Shall not exceed 2% no load to full load, measured line to neutral.

2.3.13 Voltage Transient:
100% load step plus or minus 12%. Loss or return of AC input – Plus or minus 1%.

2.3.14 Overload Capacity:
Satisfactory overload/over current operating time is based on no more than one overload in any (4) consecutive hours of operation. The UPSC should be able to facilitate the following overload scenarios: 110% (Continuous), 125% (5 Minutes), and 150% (1 Minute).

2.4 Environmental:

The equipment shall be suitable for installation indoors (altitude 0 to 1,500 meters or o to 4,900 feet) with ambient temperatures from 0° to +40°C (32° to +104°F) with 1% de-rating for each 1°C above 40°C up to 50°C, and relative humidity from 0% – 95% non-condensing.

2.4.2 Site Conditions:
  • Ambient: 0° to 40°C (32° to 104°F) (Higher/Lower Options Available).
  • Humidity: 0% to 95% Non-condensing.
  • Audible Noise: 65dB (Lower Options Available).
  • Construction: Suitable for indoor applications.
  • Service Factor: Continuous duty, 24-hour service
2.5 Physical Characteristics:

2.5.1 Rectifier:
Rectifier/Charger shall be a phase controlled rectifier design and utilize silicon controlled rectifier (SCR) thyristors. The rectifier/charger shall provide direct current to the DC bus for the inverter and battery charging functions. The rectifier/battery charger shall have sufficient capacity to support a fully loaded inverter and recharge the battery to 95% of its full capacity within 10 times the discharge time.

2.5.2 Input Protection:
Rectifier unit shall be provided with input protective devices consisting of an AC input circuit breaker. The protective device shall be capable of shunt tripping.

2.5.3 Power Walk-In:
Walk-in from 0 to 100% load shall be over a 20 second period. The rectifier/charger shall be capable of 100% step loading.

2.5.4 Battery Charging Current:
Battery charging current shall be voltage regulated and current limited. DC current limit settings shall be customer programmable. After the battery is recharged, the rectifier/charger unit shall maintain the battery at full float charge until the next operation under input power failure. The battery charger shall be capable of providing equalizing charge to the battery.

2.5.5 DC Voltage Adjustment:
Rectifier/charger unit shall have a manual means for adjusting the DC voltage for battery equalization, to provide voltage within 10% of the nominal float voltage.

2.5.6 Battery Isolation:
The UPSC shall have a DC disconnect device such as a battery contactor to isolate the module from the battery system. The disconnect device size and interrupting rate shall be based on the system’s required capacity.

2.5.7 Inverter:
The UPSC output shall be derived from a pulse width modulation (PWM) variable frequency and variable pulse width, transistorized-type inverter design and utilize insulated gate bipolar transistor (IGBTs). The inverter shall be capable of providing the specified precise output characteristics while operating over the battery voltage range.

2.5.8 Inverter Output Frequency:
The inverter shall run on an internal frequency reference.

2.5.9 Output Protection:
The output protective device shall be capable of shunt tripping and shall have an interrupting capacity as specified.

2.5.10 Internal Protection:
The UPSC module shall be self-protected against over current, sudden changes in output load and short circuits at the output terminals. The UPSC module shall have built-in protection against permanent damage to itself and the connected load for predictable types of failure within itself and the connected load. At the end of the battery discahrge limit, the UPSC module shall shut down without damage to the internal components.

2.5.11 Microprocessor Controlled Logic:
The UPSC control operations are executed through the use of microprocessor controlled logic. The microprocessor’s firmware has control over all the operations and parameters eliminating the need for most manual adjustments and potentiometers.

2.5.12 Programmable Microcontroller Unit:
A microcontroller provides the control logic with the means to interface with the various UPSC system controllers and equipment. The MCU shall be a complete and self-container control system that facilitates a very flexible and adaptable control system. The MCU system shall contain an Ethernet communication port for communicating to a remote facility management system.

2.5.13 Thermal & Sound Insulating Materials:
Thermal and sound insulating material shall be non-capillary, non-hygroscopic, and free from perceptible odors; resistant to attack by vermin, insects, rodents, and mildew; fire retardant; capable of maintaining its shape, position and consistency inherently or by suitable retaining under conditions of vibration specified herein; resistant to or protected from abrasion; and replaceable.

2.5.14 Wiring:
All UPSC wire shall be a type suitable for the application. All conductors shall be identified at both ends with 2″ of the connection point and so referenced on the drawings. Wire markers shall be thermally labeled heat shrinkable type. For terminal block requiring wire lugs pressure-type, insulated barrel ring lugs, which grip the insulation, as well as, the wire conductors, shall be used. A constant-pressure crimping tool, which conforms both crimps simultaneously, must be used. No solder connections shall be used. No wire smaller than #20 AWG shall be used, except for ribbon cable assemblies.

2.5.15 Display and Controls:
The UPSC shall be provided with a control/indicator panel. The panel shall be on the front of the UPSC module. Controls, meters, alarm, and indicators for operation on the UPSC shall be on this panel, and the following functions shall be monitored and displayed:
  • Input Voltage (Phase-to-Phase)
  • Input Current (Each Phase)
  • Input Frequency
  • Output Voltage (Phase-to-Phase or Phase-to-Neutral)
  • Output Current (Each Phase)
  • Output Frequency
  • Output Percent Load
  • UPSC Cabinet Temperature
2.5.16 Alarm Indicators:
The UPSC shall have indications for the following alarm items. Any one of these conditions shall turn on an audible alarm and the appropriate summary indicator. Each new alarm shall register without affecting the previous alarm. The UPSC will reflect the following alarm scenarios:
  • Input AC Power Source Failure
  • Overload Scenario
  • Overload Shutdown
  • System Over Temperature
  • Inverter Fault
  • Output Short Circuit Shutdown
  • Emergency Stop Condition
  • High DC Shutdown
  • Low DC Shutdown
2.5.17 Protective Controls:
The UPSC shall be built with the following protective controls:
  • Input Under Voltage
  • Input Over Voltage
  • Phase Rotation Error
  • Loss of Input Power
  • Lockable Cabinet Door
  • Output Over Voltage
  • Output Under Voltage
  • Output Overload
2.6 Construction:

2.6.1 Quality:
All materials, parts, and components used will be new and of the highest grade. Brackets and securing hardware shall be electroplated and corrosion resistant material. Internal wiring conductors shall be combined into cables, or bundles and shall be tied securely together.

2.6.2 Design:
The system shall use components of adequate rating to provide an expected service life of a minimum of ten (10) years continuous duty and five (5) years without components replacement, provided that routine maintenance procedures are conducted regularly.

2.6.3 Experience:
The manufacturer should have at least (10) years experience designing, constructing, and servicing static solid-state UPSC systems. Experience with rotary, motor generator, or flywheel UPSC systems will not be considered. Experience with other power quality products will also not be acceptable.

2.6.4 Maintainability:
No regular maintenance service operations are required, under nominal environment conditions, except for a yearly Preventative Maintenance (PM) review. A (N+X) paralleled or other unique “project specific” modifications may require a more rigorous maintenance platform in order to ensure longevity of operation and end of life (EOL). Maintenance may be done at more frequent intervals if desired.

2.6.5 System Layout:
Modules ad sub-assemblies shall be mounted in open construction design so that each may be easily replaced. The equipment shall be constructed so that each component can be replaced without the need for specialized tools.

2.6.6 Installation:
Contaminants such as magnetic, metallic, conductive, abrasive, or chemically active materials must be avoided in the airflow by effective filtering. Materials such as dust or lint, which can accumulate and block ventilation passages, must also be filtered.

2.7 Optional Features:

2.7.1 TCP/IP Over Ethernet Communication:
The UPSC will be built with RS-485 communications, which will allow real time system status, alarm indication, system measurements, and all historical information to be remotely accessed via a SNMP card TCP/IP Ethernet protocol connected directly to a HTTP server or LAN networks.

2.7.2 Outdoor Rated Enclosures:
The UPSC will be built to endure the harshest outdoor environments – sand, snow, rain, salt, etc. The enclosures will be built to NEMA 3, 3R, 4, 4X, 12…standards. For large systems (400kVA+) or “turn-key” applications the UPSC can be built into an ISO container allowing for easy transportation, placement, and maintenance.


3.1 Manufacturing:

The manufacturer shall design, build, and test the UPSC to the user’s satisfaction. If requested, the manufacturer shall arrange shipment of the UPSC to the user’s requested destination.

The manufacturer shall prepare and deliver the required drawings and manuals with the equipment.

3.2 Site Preparation:

The owner shall prepare their site for installation of the UPSC.

The owner shall arrange for local electricians to install the UPSC.

The UPSC shall be installed in accordance with local codes and the OEM’s recommendations.

3.3 Field Service, Start-up, & Inspection:

The UPSC is to be checked and inspected by the field service representative from the OEM to confirm proper installation.

The UPSC is to be started-up by the field service representative from the OEM to confirm proper operation. The OEM representative should provide commissioning, training, and other miscellaneous services required to support the UPSC installation if requested by the user.