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ITGlossary · UPS technology
Inverter
The component inside a UPS that converts DC power from batteries back to usable AC power.
Technical level:Intermediate
The inverter uses power semiconductor switches (IGBTs or MOSFETs) that switch on and off at high speed to create a 230 V / 50 Hz AC voltage from the battery's DC voltage. In an online UPS it runs continuously, while in line-interactive and offline units it only comes into action when the mains is lost.
Its quality determines the output waveform. Budget inverters produce a stepped (modified) sine wave, which can cause problems with active PFC power supplies, motors and pumps. A pure sine wave inverter delivers a waveform similar to the mains.
In solar PV the same term describes the device that converts the panels' DC into AC. When comparing products, check whether "pure sine wave" is stated explicitly.
Questions that mention it
All frequently asked questionsCan I power critical loads with a UPS and solar energy?
Yes, with hybrid systems that combine solar panels, an inverter and batteries or a UPS, so critical loads keep running during a power cut. Full independence from the grid needs a much larger system, often with a generator too.
What are the most common UPS faults?
Worn batteries, inverter failure, poor cooling, overload, or incoming voltage outside specification.
What does bypass mode mean on a UPS?
It is the mode in which the load is powered directly from the utility supply, without using the battery or the inverter.
What is start-up voltage?
The minimum voltage required for the inverter to start operating.
Related articles
Related terms
- Online (Double Conversion) UPSA UPS that continuously converts incoming AC to DC and back to AC, so the load is always fed by the inverter with clean, stable power.
- Static SwitchA thyristor-based switch with no moving parts that transfers the load between inverter and mains within a fraction of a cycle.
- Zero Transfer TimeA feature of online UPS systems, where the inverter feeds the load continuously so a power cut causes no gap at all.
- Harmonic DistortionDeviation of the waveform from a pure sine wave, caused mainly by non-linear loads such as power supplies and inverters.
- Altitude DeratingReduction in the rated power of a UPS, inverter or generator when it is installed above a certain altitude, usually 1,000 metres.
- Cold Start FunctionA feature that allows a UPS to be started directly from the battery without utility power.