Emerson 480V Manuel D’Utilisation

The parallel redundant system can noticeably improve system reliability. In normal condition, none of 

the UPS modules work at full load. That means that even if the load is increased, the system will not 

transfer to bypass. And when a UPS module shuts down due to any failure, the remaining UPS mod-

ules can still power and protect the load. When redundancy is lost due to module failure or load 

increase, the parallel system will trigger an alarm.

The parallel system also has operation modes such as normal, battery, bypass and maintenance 

bypass. All UPS modules in the parallel system operate in coordination.

• Normal Mode Operation

The load is powered by the inverters of all the UPS modules in the system. If the frequency of 

bypass is within the synchronous range, the inverter will be synchronized with the bypass. Other-

wise, the system will operate at nominal frequency.

• Battery Mode Operation

The batteries of all UPS modules power the load through their inverters. The system operates at 

nominal frequency.

• Bypass Mode Operation

The condition to transfer to bypass mode is essentially the same as that of single module system. 

The bypass of all the UPS modules powers the load.

• Maintenance Bypass Mode Operation

The sequence to transfer to maintenance bypass mode is the same as for transferring a single-

module system. The maintenance bypass switches should be switched on as synchronously as pos-

sible. Thus the system can be repaired without interrupting the power supply to critical load. If 

ECO mode is selected, the double-conversion UPS operation is inhibited at most times for the pur-

pose of saving energy. In this mode of operation, not unlike UPS of line-interactive or standby 

technology, the bypass is the preferred source. Only when the voltage and/or frequency of the 

bypass supply is beyond pre-defined and adjustable limits is the critical AC load transferred to 

the inverter.

480V DC 

Battery Input

  AC

            DC

  DC

            AC

 DC

      DC

RIB 1

RIB 2

RIB 3

RIB 4

IOB 4

IOB 3

IOB 2

IOB 1

MBB

MIB

LDB 1

LDB N