BEARING 4J3044 - Caterpillar

Manual Load Transfers
A manual load transfer between the UPS output and the alternate bypass AC source can be initiated from the UPS control panel. Manually initiated transfers are "make-before-break". The transfers utilize the UPS output and the system bypass circuit breakers.Automatic Load Transfers
An automatic load transfer between the inverter outputs and the alternate bypass AC source is initiated if an overload condition is sustained. That is, if the overload condition is in excess of the system output capability.An automatic load transfer may also be initiated due to a malfunction that would affect the output voltage. Transfers that are caused by overloads initiated by an automatic transfer of the load back to the system. The transfer occurs only after the load has returned to a level within the rating of the UPS. The system logic of the UPS allows the load to be transferred up to three times. The transfers are adjustable within 10 minute periods in order to prevent cyclical transfers which are caused by overloads. The system will be locked out in bypass mode on the fourth transfer.Momentary Overloads
The static bypass switch will connect the bypass AC source to the load and close the system bypass circuit breaker for one of the following reasons:
Load current in rush
Branch load circuit fault is in excess of the system ratingThe load transfer to bypass mode will be uninterrupted.Protection and Back Feed Prevention
The critical output bus is protected from the flow of excess current fuses. Each phase of the bypass circuit is protected by the bypass circuit breakers. Blown fuse monitors indicate when a blown fuse will prevent the static bypass switch path from being available for automatic transfers.The static bypass switch will not feed the UPS power back to the bypass distribution system, while the UPS system is operating on flywheel mode during a bypass source power outage. The static bypass switch is provided with redundant bypass power outage sensing circuits.The static bypass switch is provided with disconnects that are for redundant bypass power outage sensing. The back feed prevention system operates even if two component failures exist simultaneously. If a shorted SCR is detected, the static bypass switch is isolated. An alarm message will be annunciated at the control panel for the system cabinet. The load shall remain on conditioned power and protected power after detection of a shorted SCR and after isolation of the static bypass switch.