Frequently Asked Questions

An online (double-conversion) UPS continuously converts mains power into direct current (DC) and then back into alternating current (AC). Even when mains power is present, it always supplies the load with its own conditioned power; the transfer time is 'zero'. A line-interactive UPS, on the other hand, supplies power directly from the mains while the mains is within normal limits and switches to battery when the voltage is disturbed. Medical devices, data centers and industrial facilities should always use an online UPS.

Current standard UPS systems are built on a high-efficiency 'transformerless' architecture and are ideal for office/IT loads. However, isolation transformer UPS systems, such as those made by Tescom, are heavy-duty systems in which the input and output are physically separated (by copper windings). In hospitals, heavy industrial facilities, CNC machines and areas with highly fluctuating mains, a transformer-based UPS is an engineering necessity.

The static bypass is an electronic safeguard that automatically and seamlessly transfers the load to the mains without shutting the system down when the UPS experiences an overload or a hardware fault. The mechanical bypass is a manual switch that allows service personnel to isolate the unit's internal power during physical repairs while the loads continue to be supplied from the mains.

Direct connection is not recommended. Laser printers and induction motors draw an instantaneous inrush current of 5 to 8 times their rated power at start-up. This sudden draw causes the UPS to protect itself by going into overload. If they must be connected, the UPS capacity should be oversized to account for this starting current.

Modular UPS systems are systems in which power is provided not by a single massive block but by multiple power modules (drawer type) operating in parallel. When one module fails, the system does not stop; the other modules take over the load (N+X redundancy). When your business's energy needs grow, capacity can be increased instantly simply by inserting a new power module into the unit (hot-swap).

The crest factor is the ratio of the maximum (peak) current that can be drawn instantaneously from the UPS to the RMS current it can supply continuously. Older devices draw a 3:1 peak current, while modern computers with today's Active PFC circuits draw a smoother current (1.4 - 1.5). New-generation Sorline and Tescom units feature a flexible inverter architecture fully compatible with both load types.

In ECO Mode, to save energy, the UPS turns off online conversion while the mains is within normal limits and feeds the load from the mains via the bypass. It raises efficiency to 99%, but causes a 2-4 millisecond interruption when transferring to battery during a mains failure. It can be risky in critical data centers, but delivers significant electricity savings for less sensitive office loads.