Specifications

98AEtypMMSspec_RevB.doc
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Copyright © 2007, Mitsubishi Electric Power Products Inc.
SP-0011 Rev. B 9/5/09
bypass static switch circuit and associated control circuitry (UPS Module Control and UPS
MMS Bypass Operation Control). The same bypass source shall be connected to each
UPS Module bypass input, with each UPS Module bypass static switch circuit utilized
during UPS MMS Bypass Operation. For uninterrupted transfer of the load to the bypass
source and to UPS MMS Bypass Operation, the bypass source must be available. If the
bypass source has failed or is abnormal, the bypass source will be deemed unavailable
and an uninterrupted transfer of the critical load to the bypass source is not guaranteed.
In the event that the UPS MMS must be transferred from UPS MMS Inverter Operation
due to a system overload condition or for System Maintenance Bypass requirements, the
critical load shall be transferred without interruption to the bypass source via each UPS
Module bypass static switch circuit. The UPS MMS Bypass Operation Control in each
UPS Module will signal to the UPS Module Control to initiate transfer to bypass operation.
A paralleling, wrap-around contractor shall be used in each UPS Module bypass static
switch circuit to maintain the bypass source. Each UPS Module bypass circuit will equally
share the total load current. This condition is referred to as UPS MMS Bypass Operation
and should only be initiated during automatic emergency or manually controlled events.
F. System Maintenance Bypass/ Operation – System Maintenance Bypass Operation shall
allow total system repair and testing for parallel operation as well as individual UPS
Module repair and testing without affecting load operation. The CLC contains as standard
a System Maintenance Bypass circuit breaker (SMB) and power circuit, and a System
Output circuit breaker (52L) and output power circuit. SMB shall be a Make-Before-Break,
zero energy type circuit breaker to ensure maximum load reliability and personnel safety.
The system bypass source is a common feed to the UPS Module bypass inputs and also
the CLC System Maintenance Bypass input. An electro-mechanical interlock system will
prevent closure of the SMB circuit breaker and subsequent opening of 52L circuit breaker
unless UPS MMS Bypass Operation is active. This interlock system removes any
possibility of connecting together out of phase sources and additionally ensures a safe
operating practice and isolation procedure for system maintenance requirements.
G. Inverter and Bypass Operation Inhibit -The UPS MMS Bypass Operation Control
contained in each independent UPS Module ensures that UPS MMS Inverter and UPS
MMS Bypass Operation will never occur simultaneously. Bypass operation transfer will be
inhibited if any of the systems UPS Modules are providing load power by inverter supply.
Re-transfer operation from UPS MMS Bypass Operation to UPS MMS Inverter Operation
will be inhibited if any of the systems UPS Modules are providing load power from bypass
source supply. The same bypass source (common source) is connected to each UPS
Module bypass input therefore synchronization does not need to be considered. For
equal load sharing, a load sharing reactor shall be incorporated in each UPS Module
circuit to ensure bypass circuit impedance balance and that each bypass circuit supports
an equal share of the total load current during bypass operation. Each circuit reactor will
be located in the CLC.
H. Module Maintenance Operation - With the UPS MMS it is possible for individual UPS
Modules to be removed from the system for maintenance purposes while the remaining
UPS Modules sustain on-line power to the load from inverter supply. The configuration of
the system must be taken into consideration very carefully prior to individual UPS Module
Maintenance Operation.
I. Individual UPS Module Emergency Power Off (EPO) - When the UPS Module Emergency
Power Off (EPO) button is activated, the EPO function shuts down the UPS module. The
configuration of the UPS MMS will depict the subsequent system operation: The EPO
function can be performed both locally at the UPS Module and remotely from the CLC
System EPO button. The System EPO button shall be located on the CLC next to the