Line Interactive UPS: Popular Choice for Industries

by Roma Thomas Manager Line Interactive happens to be preferred over the other two types of UPS systems available in the market namely Offline (VFD type), and Online. Being more cost-effective than the Online variants, it also provides output voltage conditioning like voltage harmonic suppression as well as protection against transients and sags. Due to the presence of non-linear loads in the power system that distort the voltage drawn from the mains power, more current is drawn which ultimately reduces the quality and efficiency of the power fed to the entire system. These UPS systems are also capable of current harmonic suppression and reactive power compensation when they work in the standby mode.


Line interactive UPS makes use of autotransformers to counteract transients and sags. Hence, it does not require to use batteries when the voltage increases or decreases within a predefined range. This is quite beneficial in increasing the battery life. The prefix auto in the autotransformer is a misnomer as it essentially refers to the fact that this type only has one winding rather than usual two separate windings that act as primary and secondary coils. In these autotransformers, there are typically three taps to make electrical connections and to differentiate parts as primary and secondary. The added merit of using them is that they are lighter, take lesser space in the system and are cheaper than their traditional counterparts.


The working mechanism of line interactive is similar to that of offline (VFD type) systems though in this design battery is always connected to the load through the inverter and for the purpose of voltage regulation multi-tap variable voltage autotransformers are employed. The automatic voltage regulator (AVR) used in the design to protect other sensitive electrical devices makes use of the autotransformer to maintain a constant voltage at its output (in the events of transients & sags) which is then fed to the connected load through the inverter/rectifier circuit. This inverter/rectifier circuit is used for the dual purpose of charging the battery when mains power is present and to convert DC from the battery to AC for powering the connected load in the case mains is absent or has gone out of the predefined values.

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Created on Dec 31st 1969 18:00. Viewed 0 times.

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