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ITGlossary · UPS technology
Static Bypass
An electronic path inside the UPS that instantly and automatically transfers the load to the mains on overload or internal fault.
Technical level:Intermediate
The static bypass is an electronic path inside the UPS that connects the load directly to the mains, bypassing the rectifier and inverter. It activates automatically when the UPS has an internal fault, is overloaded, or when a load's inrush current exceeds what the inverter can deliver.
Thanks to it, the load stays powered instead of shutting down. It is found mainly in double-conversion (online) UPS units, from small models up to large three-phase systems. While the load is on bypass, however, it draws power straight from the mains with no protection against outages.
If the UPS frequently switches to bypass, it is usually overloaded: check the actual consumption against the rated power.
Related terms
- Transformerless UPSModern UPS design that omits bulky transformers to improve efficiency and reduce size.
- BypassA path that feeds the load directly from the mains, without protection, when the UPS is overloaded, faulty or under maintenance.
- Electromagnetic Interference (EMI)Unwanted electrical noise or interference that can disrupt electronic equipment operation.
- TransformerAn electrical component that changes voltage levels or isolates circuits.
- OverloadA condition where the connected load exceeds the UPS’s rated output in VA or W.
- Noise (Electrical)Unwanted high-frequency disturbances on the supply voltage, e.g. from motors or power supplies, which UPS systems and line conditioners filter out.