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Extended Load Bus Synch (ELBS)

Guide Spec Addendum

1.0 Description

The Extended Load Bus Synch (ELBS)option is an add on enhancement to Liebert/Emerson

Uninterruptible Power Systems (UPS). Its purpose is to ensure synchronous operation of two or more

independent (as opposed to parallelled) UPS systems during all steady state operating conditions. This

includes times when the UPSs are operating on battery and situations when the bypass inputs are out of

phase or synch.

2.0 Operation

The ELBS option performs the following functions:

a. Continuously senses the phase relationship between the outputs (critical bus) of one or more

Designated Slave System (DSS)UPSs and a Designated Master System (DMS), which is

another UPS.

b. If the systems lose synch with each other for more than a pre-determined period of time

(adjustable from 0.1 to 5 seconds), the ELBS will synch the DSS to the DMS if the Auto/Manual

switch is in the Auto Position. Synchronisation is accomplished by switching the line synch

reference in the DSS from its own bypass input to the critical bus of the DMS.

c. Bypass input voltage to the DSS is continuously monitored for quality and synch. Once quality of

the bypass and synch between the DSS critical bus and the bypass input have been re-established

for five seconds, the ELBS will revert to internal line synch with the bypass.

d. The DMS shall be selected via a rotary select switch in the Master Select and Distribution

Assembly (MSDA). Normally the largest system in the group would be the DMS (see Note

below). A second system can be manually selected in the event the original DMS is unable to

perform its duties. This MSDA will house the terminal blocks and fusing for the synch reference

signals that fan out to all of the UPS in the grouping. This will be the only common point of

coupling between the various UPS. There will be no logic-level connections between UPS,

resulting in maximum independence of systems, but retaining the ability to keep all systems in

synch.Note: If one of the systems is nota Liebert UPS, that system will be the full-time DMS,

since it will not be capable of changing its synch in response to the ELBS controls.

e. In the event the synch voltage for the DMS system should become unusable, the individual UPS

will resort to internal synch, which will be either internal bypass voltage (if in tolerance) or

internal oscillator.

3.0 Configuration:

a. The ELBS system will consist of one ELBS assembly for each UPS involved, plus ELBS

interface circuitry in each UPS (single module systems) or in each System Control Cabinet (SCC)of multi-module systems. In addition, there will be one MSDA containing the hardware necessary

to handle the number of UPS to be synchronised, plus any future expansion.

b. The ELBS assemblies shall be packaged in wall-mount enclosures, with each mounted as close as

possible to the UPS being controlled.

c. The MSDA shall also be packaged in a wall-mount enclosure and installed near whichever UPS

is chosen as the DMS.

Extended Load Bus Synch Specification 1


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2 Extended Load Bus Synch Specification

4.0 Indicators and Alarms

a. LBS Enabled.Indicates that load bus synch circuitry is enabled.

b. System Non-Synch. Indicates that the associated UPS is no longer synchronised to the other

UPS (or the DMS). This alarm will indicate during the transition from internal bypass synch to

DMS synch.

c. LBS Active.Indicates that the LBS circuitry has taken over the synch of the UPS. If the SystemNon-Synch is also on, it indicates that the synchronisation is in process.

d. Load Synch To DMS.Indicates that the UPS critical bus is synchronised to the DMS. This

indicator will turn on when the synch process is complete.

e. Indicators a through d abovecan be supplied with optional remote Form C dry contacts.

5.0 Controls

On the ELBS Assembly:

a. Mode Select Switch. Provides manual selection of Auto or Off mode. In the Auto mode, the

ELBS will be enabled. In the OFF mode, the UPS associated with the ELBS will synchronise

independently of all other UPS.

b. Lamp Test. Push to test indicator lights.

On the MSDA Assembly:a. Master Select Switch. Provides manual selection of DMS source. Two UPS feed the MSDA, so

the selection of the DMS would be either Source 1 or Source 2, with Source 1 being the first

choice and Source 2 being the contingency source.

b. Source 1 Available. Indicates that Source 1 voltage is available at the MSDA.

c. Source 2 Available. Indicates that Source 2 voltage is available at the MSDA.


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Load Bus Synch (LBS)

Guide Spec

1.0 Description

The Load Bus Synch (LBS)option is an add-on enhancement to Liebert/Emerson Uninterruptible Power

Systems (UPSs). Its purpose is to ensure synchronous operation of two or more independent (as opposed

to parallelled) UPS systems during all steady state operating conditions. This includes times when the

UPSs are operating on battery or generator, and situations when the bypass inputs are out of phase or

synch.

2.0 Operation

The LBS option shall perform the following functions:

a. Continuously sense the phase relationship between the outputs of the two UPSs that make up the

system.

b. If the two systems lose synch with each other for more than a pre-determined period of time

(adjustable 0.1 to 5 seconds), the LBS will synch the Designated Slave System (DSS)to the

Designated Master System (DMS)if the Auto/Off switch is in the Auto position.

c. Continuously monitor the quality and synch of the bypass input voltage to both systems. Oncequality and synch between the two have been re-established for five seconds, the LBS will revert

to separate synch for both systems, each synchronised to its own bypass.

d. DSS and DMS are selected manually via the Master Selectswitch on the LBS controller

enclosure. If the DSS is on bypass and unable to synch to the DMS, the DMS will then synch to

the output bus of the DSS. This re-selection of master will be accomplished automatically. The

controller enclosure shall house the terminal blocks and fusing for the synch reference signals of

the two UPSs. There will be no logic-level connections between UPSs; this shall provide

maximum independence between systems while retaining the ability to keep the systems in synch.

e. Failure of any part of the LBS controls will not cause system failure. The worst case effect of a

failure in the LBS will be a failure of the two systems to synchronise with each other during times

when both systems are not synchronised to utility power.

3.0 Configuration

The LBS system will consist of a controller that fits into a compact 500 x 600 mm (20x24 inch)

enclosure. In addition, LBS interface cards will be installed installed either in each UPS (single module

systems) or in each System Control Cabinet (multi module systems). Front panel controls on the LBS

shall be simple and fault tolerant and enable the operator to select:

a. Whether the circuit will function automatically or be Off, and

b. Whether UPS #1 or UPS #2 will be the Designated Master System (DMS). The other UPS system

then becomes the Designated Slave System (DSS).

4.0 Indicators and Alarms

a. LBS Enabled. Indicates that the load bus synch circuitry is active.

b. System Non-Synch. Indicates that the DSS is no longer in synch with the DMS. This alarm willindicate during the transition from internal bypass synch to DMS synch.

c. LBS Active. Indicates that the LBS circuitry has taken over the synch of the UPS. If the System

Non-Synch indicator is also on, it means that synchronisation is in process.

d. Load 1 Synch to Load 2. Indicates that the UPS critical bus is synchronised to the bypass input

of the DMS, in this case UPS #2. This indicator will turn on when the synch process is complete.

e. Load 2 Synch to Load 1. Indicates that the UPS critical bus is synchronised to the bypass input

of the DMS, in this case UPS #1. This indicator will turn on when the synch process is complete.

Load Bus Synch Specification 1


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2 Load Bus Synch Specification

f. All indicators mentioned above can be supplied with Form C dry contactsfor remote

monitoring, if desired.

5.0 Controls

a. Mode Select Switch. Provides manual selection of Automatic operation or Off mode. In the

Automatic mode, the LBS will be enabled. In the Off mode, both UPSs will synchronise

independently.b. Master Select Switch. Provides manual selection of the DMS source. The LBS circuitry will

automatically switch DMS sources should the initially selected DMS lose its bypass input.

c. Lamp Test. Push this button to test indicator lights.

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