Specifications

98AEtypMMSspec_RevB.doc

SP-0011 Rev. B 9/5/09

static switch and shall at the same time as the static switch, be energized and

upon closure maintain the critical load feed from the bypass source. The static

switch shall only be utilized for the time needed to energize the wrap around

contactor therefore increasing reliability. The bypass circuit shall be capable of

supplying the UPS rated load current and also provide fault clearing current

capabilities. The UPS MMS Bypass Operation Control, will upon signaling the

UPS Module Control to initiate transfer to bypass operation, cause the static

switch to energize within 150μs, therefore providing an uninterrupted transfer

to the bypass source (UPS MMS Bypass Operation).

C. In relation to automatic re - transfer from UPS MMS Bypass Operation to UPS

MMS Inverter Operation upon overload clearance. The UPS MMS Bypass

Operation and UPS Module Control shall allow a re-transfer to occur three

times maximum within a one minute period. Re-transfer shall be inhibited upon

the fourth request for protection from a suspect recurring problem at the UPS

load distribution.

D. With each UPS Module incorporating an independent automatic bypass static

switch circuit and associated control; system reduction with the capability to

utilize the removed UPS Module for Single Module System (SMS) application

or other system configurations is possible. This feature results in high system

flexibility, with ease of expansion or reduction of the UPS MMS.

2.2.6. UPS MMS Control

UPS MMS Control, incorporating UPS MMS Parallel and Bypass Operation

Control in each UPS Module utilizes cross current control and inverter operation

logic signals between the UPS Modules to ensure correct UPS MMS operation.

A. UPS MMS Bypass Operation Control:

1. The UPS MMS Bypass Operation Control contained in each independent

UPS Module ensures correct system transfer to and re-transfer from

bypass operation and that UPS MMS Inverter and Bypass Operation will

never occur simultaneously.

2. Referring to the previous section UPS Module Inverter Shutdown,

subsequent to a UPS Module inverter shutdown, the shutdown UPS

Module inverter will automatically isolate from the system, with the UPS

MMS Bypass Control activating a control sequence that upon completion

will signal the UPS Module Control to initiate transfer to bypass operation.

The completion of this control sequence and subsequent initiation of

transfer to bypass operation will be inhibited while the remaining system

UPS Modules can sustain load power from inverter supply.

3. When the UPS MMS Bypass Operation Control in each UPS Module

signals the UPS Module Control to initiate transfer to bypass operation and

therefore initiate system transfer to UPS MMS Bypass Operation, each

UPS Module will transfer to the bypass static switch circuit simultaneously.

4. Re-transfer operation from UPS MMS Bypass Operation to UPS MMS

Inverter Operation will be inhibited if any of the systems UPS Modules are