Typical Ratings
40–750 kVA/600 kW, and higher when multiple units are paralleled.
Typical Static UPS Configurations Static UPS systems modules are available in three basic types of configurations known as standby, line interactive and double conversion.
See Tab 33 in this guide for details on all the UPS configurations available from Eaton. The lighter power ratings are likely to be one of the first two types of configurations, e.g., standby or line interactive. Most medium or large static UPS installations use the double conversion technology in one or multiple module configurations, i.e., or multiple UPS units in parallel.
Figure 1.4-19 illustrates the one-line diagram of a simple single Double Conversion UPS module. Brief explanations appear for the standby and line interactive UPS systems after the text explaining the Double Conversion static UPS type of system.
A. Double conversion concept of operation—the basic operation of the Double Conversion UPS is:
1. Normal power is connected to the UPS input through the facility electrical distribution system.
This usually involves two input circuits that must come from the same source.
2. The Rectifier/Charger function converts the normal AC power to DC power to charge the battery and power the inverter. The load is isolated from the normal input source.
3. The battery stores DC energy for use when input power to the UPS fails. The amount of power available from the DC battery system and time to discharge voltage is a function of the type of battery selected and the ampere-hour sized used. Battery systems should be sized for no less than 5 minutes of clean power usage from a fully charged state, and, in many cases, are sized to provide more time on battery power.
4. The DC link connects the output of the rectifier/charger to the input of the inverter and to the battery.
Typically the rectifier/charger is sized slightly higher than 100% of UPS output because it must power the inverter and supply charger power to the battery.
5. The bypass circuit provides a path for unregulated normal power to be routed around the major electronic sub-assemblies of the UPS to the load so that the load can continue to operate during maintenance, or when the UPS electronics fails. The bypass static switch can switch to conducting
mode in 150–120 milliseconds.
When the UPS recognizes a requirement to transfer to the bypass mode, it simultaneously turns the static switch ON, the output breaker to OPEN, and the bypass breaker to CLOSE. The output breaker opens and the bypass breaker closes in about 50 milliseconds. The restoration of normal conditions at the UPS results in the automatic restoration of the UPS module powering the load through the rectifier/charger and inverter with load isolation from power quality problems, and the opening of the bypass circuit.
Static Double Conversion Advantages
■ Addresses all power quality problems
■ Suitable for applications from 5 kVA to over 2500 kVA
■ Simple battery systems are sized for application
■ Long battery backup times and long life batteries are available
■ Higher reliability is available using redundant UPS modules
Figure 1.4-19. Typical Static UPS, Double Conversion Type with Battery Backup Source
Battery AC
DC
DC AC
Inverter Output
Breaker Normal
Breaker
Bypass Static Switch
UPS Module
Load Rectifier/Charger
Battery Breaker Bypass Breaker (Optional)
1.4-29
April 2016
i ii 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Sheet 01
Uninterruptible Power Systems (UPS)
085
Static Double Conversion Disadvantages
■ Battery systems, battery maintenance and battery replacement are required
■ Large space requirement for battery systems (higher life takes more space, e.g., 500 kW takes 80–200 sq ft depending upon the type of battery used, VRLA 10 year, VRLA 20 year or flooded)
■ Limited discharge cycles of battery system
■ Narrow temperature range for application
■ Efficiencies are in the 90–94%
range, which is lower than some line interactive configurations
■ Bypass mode places load at risk unless bypass has UPS backup
■ Redundancy of UPS modules results in higher costs
■ Output faults are cleared by the bypass circuit
■ Output rating of the UPS is 150%
for 30 seconds
■ Battery disposal and safety issues exist
B. Standby UPS concept of
operation—The basic operation of the Standby UPS is:
1. The Standby UPS topology is similar to the double conversion type, but the operation of the UPS is different in significant ways.
Normal power is connected to the UPS input through the facility electrical distribution system.
This usually involves two input circuits that must come from the same source. See Figure 1.4-20 for details.
2. The rectifier/charger function converts the normal AC power to DC power to charge the battery only, and does not simultaneously power the inverter. The load is connected to the input source through the bypass static switch.
The inverter is in the standby mode ready to serve the load from battery power if the input power source fails.
3. The battery stores DC energy for use by the inverter when input power to the UPS fails. The amount of power available from the DC battery system and time to discharge voltage is a function of the type of battery selected and the ampere-hour sized used.
Battery systems should be sized for the anticipated outage.
4. The DC link connects the output of the rectifier/charger to the input of the inverter and to the battery.
Typically the rectifier/charger is sized only to supply charger power to the battery, and is rated far lower than in the double conversion UPS.
5. The bypass circuit provides a direct connection of input source to the load. The load operates from unregulated power. The bypass static switch can switch to non-conducting mode in 150–
120 milliseconds. When the UPS recognizes the loss of normal input power, it transfers to battery/
inverter mode by simultaneously turning the Inverter ON and the static switch OFF.
Static Standby UPS Advantages
■ Lower costs than double conversion
■ Rectifier and charger are economically sized
■ Efficient design
■ Batteries are sized for the application
Static Standby UPS Disadvantages
■ Impractical over 2 kVA
■ Little to no isolation of load from power quality disturbances
■ Standby power is from battery alone
■ Battery systems, battery mainte-nance and battery replacement are required
■ Limited discharge cycles of battery system
■ Narrow temperature range for application
■ Output faults are cleared by the bypass circuit
■ Battery disposal and safety issues exist
C. Static line interactive UPS concept of operation—the basic operation of the Line Interactive UPS is:
1. The Line Interactive type of UPS has a different topology than the static double conversion and standby systems. The normal input power is connected to the load in parallel with a battery and bi-directional inverter/charger assembly. The input source usu-ally terminates at a line inductor and the output of the inductor is connected to the load in parallel with the battery and inverter/
charger circuit. See Figure 1.4-21 for more details.
2. The traditional rectifier circuit is eliminated and this results in a smaller footprint and weight reduction. However, line conditioning is compromised.
3. When the input power fails, the battery/inverter charger circuit reverses power and supplies the load with regulated power.
Static Line Interactive UPS Advantages
■ Slight improvement of power conditioning over standby UPS systems
■ Small footprints and weights
■ Efficient design
■ Batteries are sized for the application
Static Line Interactive UPS Disadvantages
■ Impractical over 5 kVA
■ Not as good conditioning as double conversion
■ Standby power is from battery alone
■ Battery systems, battery mainte-nance and battery replacement are required
■ Limited discharge cycles for the battery system
■ Narrow temperature range for application
■ Battery disposal and safety issues exist
1.4-30
April 2016
i ii 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Sheet 01
Uninterruptible Power Systems (UPS)
086
Figure 1.4-20. Typical Static UPS, Standby Type with Battery Backup
Figure 1.4-21. Typical Static UPS, Line Interactive Type with Battery Backup Source
AC
DC
DC
AC UPS Module
Normal Breaker
Rectifier/
Charger Inverter
Bypass Static Switch
Battery Breaker
Output Breaker
Battery
Load
Source
DC
AC
UPS Module
Bidirectional Inverter/Charger
Battery
Load Inductor
1.4-31
April 2016
i ii 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Sheet 01
System Application Considerations
Other Application Considerations
087