There are three different types of UPS systems-Standby, Line-interactive and Double conversion systems. There are two kinds of waveforms that are output by the UPS. These are square sine wave and true sinewave.
The basic purpose of an Uninterruptible Power System (UPS) is to provide power to attached loads when the electricity supplied by the utility grid is of inferior quality that may damage the equipment or there is an event of power failure. Whatever be the case, the output waveform supplied by the UPS must correspond with the power supply of the server.
There are three different varieties of UPS systems-standby systems, line-interactive systems, and double conversion systems. Though they are different, they have some things in common. They all have a battery bank, charger, input circuitry and a DC/AC inverter. All these UPS models shell out a voltage waveform depending on the type of its DC/AC inverter (pure sine wave or modified sine).
The modified sine wave or square wave inverter is usually used in low-priced UPS devices. Inverters manufacturers mention output from such an inverter as several names like step-approximated, modified or pulse width-modulated (PWM) sine wave. This waveform comprises of zero-voltage zones between every negative and positive half-cycle. Besides, various models have an amplified voltage slew rate (rate-of-change) resulting in ringing between the input elements of power supply and the output elements of the UPS that causes current peaks and higher voltage. Certain square wave systems have slower voltage slew rates and include extra output elements to decrease the destructive ringing between the power supply and UPS. But because of such additional features, the cost of ups increases and that is the reason that they are normally not the part of the low-end UPS models. These work effectively with the pure inductive loads like blenders and mixers, as well as the pure resistive loads like heaters and lamps. But these do not work well with the computer power supplies as they lead to the systems running hotter with reduced efficiency and thus shorten the working life.
The sophisticated line-interactive and double conversion sine wave home UPS models output excellent quality sine wave that is really similar to a utility AC power sine wave. A pure sine wave DC/AC inverter is chosen when it is employed with the server and storage power supplies. To conclude, it is advised that in order to ensure maximum protection during the sudden utility outages, a UPS that has a inverter is used. For smaller needs like the pure inductive and pure resistive loads, ups with modified this inverter with additional features can be used.
