Why inverters and UPS fail (Part-2)

Power disturbances may lead to a lot of things. Sags and under voltages can cause component overheating or destruction. Component overheating reduces the life and deteriorates the real reliability as opposed to the estimated reliability based on steady-state conditions of the product.

Most of the semi-conductors fail as they are intolerant to surge voltages in excess of their voltage ratings. Even a fast surge of a few microseconds can cause the semi-conductor to fail catastrophically or may degrade it so as to shorten its useful life. Damage generally occurs when a high reverse voltage is applied to a non-conducting PN. The junction may avalanche at a small point due to the non-uniformity of the electric field. In this case, thermal runaway can occur because of localized heat build up and cause a melt-through which destroys the junction.

Due to many reasons even the current solutions to these typical problems fail. Typical EMI filters used in most systems are not well damped. This has a dramatic effect on any voltage disturbances, resulting in oscillations inside the EMI filter under any transitional conditions. Severe voltage surges may result from fly-back from saturated inductors looking for a path to release energy. Boost converters can be destroyed by surges causing increased energy storage in input filter, the output capacitor (c) is charged to an unsafe level depending on capacitance value and load levels for the dc/dc converter connected to the output of the boost.

Installation and wiring practices are very important to ensure a reliable installation. But some typical problems are commonly experienced. They are like: Inadequate wire size or type, Long overloaded wire runs, Too many loads on a branch circuit, Poor connections, Ground currents due to incorrect wiring, Systems that do not have a clear path to ground for fault currents have to rely on ground fault detection that sometimes malfunctions, Mixing electrical equipment that is designed for different standards, Overloaded utility transformers and Incorrectly applied surge protection devices.

Commercial Inverters and UPS Equipments have certain limitations as well. They are as follows:

1. Because of the frequency of power disturbances, the power electronic circuitry in the Inverter/UPS must work far more often and under greater stress. This is especially true for Inverters and Line Interactive UPS which must make the transfer to battery backup every time there is a power disturbance. Also the power transistors and transformers must operate at higher current and voltage levels during brownout and over voltage conditions, resulting in a shorter-than-normal operating lifetime of the Inverter / UPS systems.
2. Stand-by power generators such as DG sets can cause special problems for when they are used to power an Inverter/UPS system. They are known to produce wide frequency/voltage fluctuations, surges/spikes, and highly distorted (often non sinusoidal) outputs which can cause continuous mains/inverter transfer operations, shutdowns, and even catastrophic failure.
3. If the ambient temperature is outside of the optimum 10 to 25 degree C range, standard flooded lead-acid batteries cannot be used. Standard flooded batteries are rated to work only when temperature is above 0 degree C, and sudden battery failure can occur when operating temperature goes above 40 degree C. Even at 30 degrees C, expected battery lifetime is reduced by 50% compared to the expected battery lifetime at 20 degrees C.
4. Limitations include sites subjecting to frequent lightning strikes, absence of a coordinated surge protection system may cause premature failure due to unmitigated surges and spikes induced on incoming ac power line(s).
5. Moreover the industry is driven by low cost and users normally do not care much about power quality.

But Su-Kam has come up with a reliable and consistent solution for these problems. The R&D team of Su-Kam has managed to develop an intelligent application of technology coupled with an intimate familiarity with the nature of power problems persisting in India. Su-Kam has developed a family of Inverter/UPS systems that are best suited for developing countries like India. Su-Kam has been serving you since the 1990’s and will continue to deliver their best in future as well.

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