UPS 250, UPS 300, UPS 301, UPS 500, UPS 600, UPS 750 and UPS 900 Uninterruptible Power Supplies Caterpillar

Overview

The Caterpillar Uninterruptible Power Supply (UPS) is a fully integrated line-interactive system that uses a flywheel to store mechanical energy in the form of a rotating mass. When power from the utility is interrupted, the UPS will convert the energy that is stored in the flywheel to electrical energy. This energy is supplied to the external load until one of the following conditions occur:

• The standby generator assumes the load.

• The utility power is available again.

• The flywheel runs out of energy.

Once utility power returns, the system will transfer the load back to utility power without interruption.

The UPS can be used in a wide range of commercial power applications. The systems provide voltage regulation and protection from power outages. This is done in order to provide well regulated power for the following situations: critical loads, sags, surges and outages.

Single Module System (SMS)

The SMS is distinguished from the Multiple Module System (MMS) by a single Flywheel Cabinet that is bolted to the Bypass Cabinet. The Bypass Cabinet is available in two different sizes. The width of the cabinet is dependent on the type of wiring for the system. The four-wire cabinet is wider than the three-wire cabinet.

Multiple Module System (MMS)

The MMS is different from the SMS. The MMS contains a MMU Cabinet, an Input/Output Cabinet and a System Cabinet. The MMS is an expandable ready system. A MMU can be added to a system if an expanded run time or a higher power requirement is present.

MMS (N+1)

The MMS (N+1) is sized with an additional MMU. A MMU is disconnected from the load of the facility when the MMU has an internal failure. The additional MMU will continue to carry the load. The MMU with the failure can be repaired. Once the MMU is reconnected to the load the system can resume redundant operation.

Cabinets

The components of the UPS are contained in steel cabinets. The systems consist of following cabinets:

• The Input/Output Cabinet

• The System Cabinet

• Flywheel Cabinet

• The MMU Cabinets

The cabinets are transported as individual units. The units are delivered separately. The units are assembled at the site of installation. The Input/Output Cabinet weighs 590 kg (1300 lb). The System Cabinet weighs 386 kg (850 lb). The MMU Cabinet weighs 2041 kg (4500 lb).

Table 1 describes the configuration of each type of system.

Input/Output Cabinet

The Input/Output Cabinet can be configured for either single input or for dual input. The Input/Output Cabinet contains the following components:

• Power Cable Connections

• Maintenance Bypass Switch (optional equipment)

• Input Isolation Switch (optional equipment)

• Bypass Input Switch (optional equipment)

• Output Isolation Switch (optional equipment)

• Air Filters

Refer to Product Information Section, RENR2476, "Model Views" for more information on the location of the components that are listed above inside of the cabinet.

System Cabinet

The System Cabinet contains the following components:

• User Interface Panel for the System

• Static Bypass Switch (optional equipment)

• Output Isolation Switches for MMU (optional equipment)

• Input Isolation Switches for MMU (optional equipment)

• Bypass Circuit Breaker

• Modem

• Ethernet

• Zig zag transformer (optional equipment)

• Air Filters

Refer to Product Information Section, RENR2476, "Model Views" for more information on the location of the components that are listed above inside of the cabinet.

Multiple Module Unit Cabinet

The Multiple Module Unit Cabinet contains the following components:

• User Interface Panel for the MMU

• Flywheel Energy Storage System

• Vacuum Pump

• Emergency Power Off Reset Circuit Breaker

• Air Filters

Refer to Product Information Section, RENR2476, "Model Views" for more information on the location of the components that are listed above inside of the cabinet.

The optional (N+1) system is equipped with an additional MMU. In this configuration, the loss of one MMU will not cause the system to drop the critical load. When a malfunction occurs in the MMU, the MMU will be disconnected from the critical load. The remaining MMU(s) will continue to carry the load. After the MMU(s) has been repaired, the units can be reconnected to the critical load and the units can resume redundant operation. The load will automatically transfer the bypass line without interruption if the following conditions occur: removal of the MMU(s) from the system and exceeded load capacity of the MMU(s). Any redundant MMU(s) can manually be removed from the critical load for maintenance without disturbing the critical load bus. In this case, the isolation switches are used.

Theory of Operation

Simplified block diagrams of the system are represented by illustration 1 through illustration 2. The nodes determine the state of the system. The input node and the output node are externally available. These nodes are used in order to attach the system to a power source and to the load. The inverter node is used internally by the system.

The DC bus is used as a power source for the following items: Field Coil Currents, Voltage Regulation, Harmonic Cancellation, Power Factor Correction and Flywheel Motor-Up. The mode of the system determines if the bus is used as a power source for the flywheel or if the bus is used as a power source for the utility converter.

A description of each component is in the following list:

Input Contactor ("K1") - The input contactor is a electrically operated mechanical contactor that is used to control the flow of electricity into each MMU.

Output Contactor ("K2") - The output contactor is a electrically operated mechanical contactor that is used to control the flow of electricity from each MMU.

Bypass Circuit Breaker ("K3") - The bypass circuit breaker is an electrically operated circuit breaker that is used to bypass the system.

Static Switch ("K4") - The static switch is a semiconductor device (thyristors). The static switch is used to isolate each MMU from the utility grid when an "Out of Tolerance" condition occurs.

Flywheel Converter - The flywheel converter is a semiconductor device that is bidirectional. The flywheel converter converts DC power into AC power. This is done in order to make sure that the flywheel continues to spin at full speed whenever the utility power is available. When utility power is not available, this converter rectifies the AC power from the flywheel into DC power.

Utility Converter - The utility converter is a semiconductor device that is bidirectional. The utility converter converts the voltage from the AC bus inverter node to DC voltage in order to charge the DC bus for the flywheel converter. When the utility power is not present, the utility converter converts the DC power from the DC Bus into AC power for the load.

The Utility Converter also performs the following functions:

• Voltage Regulation

• Harmonic Cancellation

• Control of the Power Factor During On-line Operation of the UPS

Block Diagrams of the Systems

System Diagram for an SMS

Illustration 1	g01777434

System Diagram for a MMS

Illustration 2	g01777440