SCREW 5404833 - Caterpillar

(N+1) Option
A UPS with the (N+1) Option is sized with an additional Multiple Module Unit. In this configuration, the loss of one Multiple Module Unit will not cause the system to drop the critical load. The Multiple Module Unit will be disconnected from the critical load when a malfunction occurs in the Multiple Module Unit. The remaining Multiple Module Units will continue to carry the load. After the Multiple Module Unit has been repaired, the unit can be reconnected to the critical load and the Multiple Module Unit can resume redundant operation.The load will be transfered to the bypass line without an interruption in the power if more than one Multiple Module Unit is removed from the system and if the load exceeds the capacity of the Multiple Module Units that are remaining.Any redundant Multiple Module Units can be disconnected from the critical load manually for maintenance without disturbing the critical load bus. In this case, the isolation switches are used.Systems without a Redundant MMU
In a system without a redundant MMU, all the Multiple Module Units will supply the full rated load. If the Multiple Module Unit malfunctions, the load will be transfered to the bypass line without an interruption.Load Sharing
In parallel operation, all inverter units automatically share load at all times. The output current of individual Multiple Module Units will be no more than 5% unbalanced. Parallel load sharing is programmed within each Multiple Module Unit. In systems with the (N+1) option, the redundant Multiple Module Unit only shares the reactive current.Manual Transfer of the Loads
A manual transfer of the load between the output of the UPS and the alternate source of power can be initiated from the control panel on the System Cabinet. Manually initiated transfers are "make-before-break". A manual transfer utilizes the following devices: the output of the UPS and the circuit breakers for the bypass circuit (system).Automatic Transfers of the Load
An automatic transfer of the load between the inverter outputs and the alternate source of power is initiated if an overload condition is sustained for a time period in excess of the capability of the system output. An automatic transfer of the load may also be initiated due to a malfunction that would affect the output voltage. Transfers that are caused by overloads are transfered back to the system again, only after the load has returned to a level within the rating of the UPS. The logic of the UPS will allow the UPS to transfer back to the system up to 3 times. The time period for the UPS to transfer back is adjustable within ten minute periods in order to prevent cyclical transfers which are caused by overloads. When the UPS attempts to transfer the load on the fourth time, the system will be locked out in bypass mode.Momentary Overloads
The static switch will connect the bypass AC source to the load. Additionally, the static switch will close the circuit breaker for the system bypass in one of the following cases:
inrush of load