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UPS For Significant Equipment UPS Input with External Power Plant

UPS For Significant Equipment

Normally, most significant equipment have non-linear loads. Because the equipment uses a configuration of diodes at the input. Which generate a distorted current, both in stable regime and in fault conditions. APC UPS price in Pakistan.

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Devices Used With UPS

To always achieve the continuity of the voltage waveform with the characteristics required by the load and with the minimum possible. THDv both on the load side and at the input of the supply transformer, different devices used. One of the most efficient is the UPS. Most UPS systems designed with 1-phase input converters, but these cause a higher harmonic content compared to a 12-phase converter.

UPS Input

As shown in the figure, the UPS input is through a three-phase transformer, where the secondaries connected in delta and star to ensure that the transformer outputs are out of phase by 30° between them. Therefore, fixing the value of the voltage so that the two outputs have the same value, the two converters powered in such a way that each one makes six commutations in each period of the network voltage, that is, every 16.66 ms.

Input Of the Power Transformer

A phase shift of 30° is achieved from the input of the power transformer, so that they are seen as a single twelve-phase converter. This effect allows a reduction of harmonics, both on the alternating current side and on the direct current side, that is, towards the batteries. APC UPS price in Pakistan.

Classic Scheme of A UPS With a Twelve-Phase Converter

The content of current harmonics generated in a converter that works under ideal conditions, that is, supplied with infinite short-circuit power, defined by the following equation:

n = kp ± 1 con In = I/n (1)

where n is the order of the harmonic, k is an integer (1, 2, 3,), p is the number of pulses in each period of the voltage and I n is the breadth of the harmonic.

Converters Modulus in Alternating Current

In this case, if the two converters work correctly, the 5th and 7th harmonics (the highest in modulus) disappear. And the first harmonic on the alternating current (ac) side will be the 11th harmonic. Which greatly reduced if a shunt filter with good efficiency introduced, also managing to reduce, although to a lesser extent, the 13th harmonic, and the successive ones. APC UPS price in Pakistan.

Important Element for the UPS

On the direct current side, the 12-phase converter always and in a controlled way supplies the batteries with a reduced ripple compared to a 12-phase converter. The next stage is a first-order filter (inductor) whose function is to further reduce the ripple, thus increasing the useful life of the batteries, which are an important element to guarantee the autonomy that the UPS can provide to the equipment since perform the following functions:

  • They eliminate the small residue of the ripple on the direct current side, improving the quality of the PWM (Pulse Width Modulation) of the inverter.
  • Depending on the number of total Ampere-hours, they set the necessary autonomy for the load it supplies in conditions of absence of electrical energy.

Autonomy Of The UPS

The autonomy of the UPS must be sufficient, at least for the time required for the longest surgical operation that carries out in the hospital. Due to this, the required autonomy times can be considerable. Therefore, all possibilities consider to maximize the guarantee of absolute power continuity.

Step 1:

(Maximization of autonomy): proceed to disconnect in coordination, automatically or manually, with a technical criterion based on medical necessity, the loads under UPS that are not vital in this period, to increase the established autonomy of machine.

Step 2:

In the event of an extended power outage, interconnect to an external plant, so that the system can continue to function normally with a continuous input flow.

Conditions To Charging with External Power Plant

In conditions of prolonged absence of power, there must be the possibility of charging the UPS input through an external power plant, in such a way as to guarantee an energy input that leads to maintaining the autonomy condition to safely supply the required service. Naturally, the autonomy of the batteries is proportional to the actual load of the UPS, so it is greater the lower the load.

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