The installation of uninterrupted power supply (UPS)

The installation of an uninterruptible power supply (UPS) is a critical procedure. For example, a corporation that intends to acquire and install electrical equipment needs have precise data on power usage in order to install a sufficient and continuous power supply (Nayar, Ashari, and Keerthipala, 2000 p. 348). In other words, before installing a UPS, assess the power consumption of the equipment as well as the overall cost of installation. In most circumstances, each piece of equipment has a tag situated where the power code enters the item (King and Knight 2002). Through the tag, electrical engineers can determine the correct amount of power supply that will allow the device operate smoothly without overloading the source or experiencing power shortage (Nayar, Ashari, and Keerthipala, 2000 p. 350). The underlying principle during UPS installation is that electrical engineers must identify at a minimum, the “voltage,” ”amperage,” and ”frequency.”

Analyzing the Size of UPS Installation

The installation of UPS begins with a comprehensive load study based on the present energy needs and planed future developments or expansions (Jungreis, Abb Power T&D Company Inc. 2001). For instance, a company that deals in computers and related service should analyze load needs while taking into consideration aspects such as the CPU, printers, disk drive, plotters, C.R.T terminals, and important peripheral devices.

Determining the Volt-Amperes

Volt-Amperes or VA is the mathematical product of voltage (V) and amperes (A) given as VA = V x A. The value VA is a conventional measure of electrical capacity power industry (King and Knight 2002). The VA’s worse case measure recognize the fact that at some point a device may consume many amperes (A) at a specific voltage. However, small equipment have their loads measured in watts (W) and not volt-amperes. Therefore, it is important to note that the ratio of W over VA is equal to power factor (energy utilization).

Power ratio = Watts (W) + Volt-amperes (VA)

Determining the Power Factor (p.f)

If we consider a computer whose VA is 120 and W equal to 96, then the power factors (p,f) can be obtained as follows:

96 W/120 VA = 0.8 p.f.

Conventionally, it is always necessary to accept a p,f if 0.8 in cases where both the wattage of VA measures are not give. Consider a situation where a company’s desktop computer has the following labeling:

CPU

B/W monitor

100 VAC to 125VAC

100VAC – 125 VAC

1.5 A

0.9 A

50HZ or 60 HZ

60 HZ

From the table above, we are not provided with the device wattage and p.f. However, with our nominal value of 120 VAC, it is possible to determine the CPU’s VA using the formula:

CPU’s VA = VCA x A = 120 V x 1.5A = 180 VA.

If we assume a p.f of 0.8, we can get wattage as follows; 180 VA x 0.8 = 144 W.

Choosing the Correct Amount of Energy Consumption

It is important to note that after the power supply installation, the 180 volt-amperes and 144 watts will be circulating between the input power source and the device in question as unused energy (Welches 2003). The decision as to which value should be used depends on an earlier statement about the desired UPS capacity. The calculation for power supply in other equipment will follow the same procedure.

Other considerations made during the UPS should relate to the lighting system, alarms, security systems, and loads to be supported during computer operations. Moreover, the installation must allow room for future expansion (Jungreis, Abb Power T&D Company Inc. 2001). After identifying the necessary devices, it would be necessary for electrical engineers to determine the voltage of each equipment (load). The voltage of every load can be single, double, or triple phase. Apart from the voltage load, it is a requirement that the corresponding cost of installation should be determined so as to reduce the size of the UPS (King and Knight 2002). In cases where loads vary in terms of input voltage input, the engineer must determine if the loads are convertible. For instance, a company’s main frame may only accept ”208Y/120 VAC triple phase” or ”240 VAC triples phase inputs” (Jungreis, Abb Power T&D Company Inc. 2001). If the company is to choose between 120 V and ”208Y/120 V, then it would be appropriate to settle for ”208Y/120 V to reduce the additional cost of installation. However, if the firm has three phase loads, then it is appropriate to install a three pages UPS.

Load Size Analysis

In summary, the first step in load analysis include the identification of loads. The second step involves balancing the loads while the third stage entails selecting UPS size. The table and calculations below summarize the three procedures.

Identification of Loads

Single phase (120 V)

Double phase (208 V)

Triple phase (208)

75.0 amp

1.5 amp

12.0 amp

0.5 amp

5.0 amp

3.5 amp

1.5 amp

7.0 amp

2.5 amp

5.0 amp

3.0 amp

Balancing Loads

Phase A

Phase B

Phase C

75.0

5.0

2.5

Single phase loads

7.0

3.0

Single phase loads

3.5

Single phase loads

0.5

Single phase loads

1.5

1.5

Double phase loads

12.0

12.0

12.0

Triples phase loads

1.5

1.5

1.5

Triples phase loads

5.0

5.0

5.0

Triples phase loads

93.5

32.5

29.5

Calculating kVA

In order to determine the lowest kVA required, it becomes necessary to find the product of highest phase current, voltage, and three. The result is then divided by 1000 as a phase value as indicated below.

k.VA =

k.VA = = 33.66 kVA.

If we are to select from the standard sizes, we are compelled to supply a triple phase of 40kVA with 111 amperes AC output for every UPS phase (Welches 2003). It is also clear from the calculations that phase ”A” will be about 84 percent loaded while Phases ”B” and ”C” will be 27 percent loaded (Jungreis, Abb Power T&D Company Inc. 2001). This leaves us with adequate space of additional single phase load that can be used for projected developments or expansions.

The analysis and discussion above revolve around the installation of UPS for equipment that require continuous load current supply (Welches 2003). It is, therefore, necessary for the installation teams to identify loads that have inrush current. Similarly, powering up current loads sequentially can help in preventing overloading, which may lead to power interruption.

The size of the UPS during the installation can be estimated in order to make accurate quotations particularly when the time available does not allow detailed load analysis. With all the devices installed and working, the electrical engineer may decide to use a clamp-on ammeter method to install the required UPS. Where the UPS is to be installed on a single phase, a two-wire system can be used to determine the hot leg while the kVA can be determined using the formula below.

kVA =

Similarly, a three-wire system of the ratio 240:120 can be used to determine every hot leg in a single phase installation. This installation process ensures that the kVA rating achieved corresponds to the highest current reading and voltage according to the formula below.

kVA =

When dealing with a triples phase system, it always recommended that each of the three hot legs should be measured. The kVA rating in this case can be determine using the formula:

kVA =

Material Selection and UPS Installation

The next stage involves making sure that the inverter is compatible with the equipment loads at a high crest capability factor. The current electronic devices and instrumentations tools have high frequency switching powers, meaning that the non-linear current can be obtained from AC sources (Nayar, Ashari, and Keerthipala 2000 p. 352). It is also necessary to maintain the power sources at sufficient level to enhance response to some of the worst case requirements for the same services. It is widely known that clients play the role of installing power energy requirements. The specific concepts studied in relation to the installation of UPS include consideration and distribution of input power (Jungreis, Abb Power T&D Company Inc. 2001). The installation process outlines specific consideration that must be made. The first consideration made is that the installation team should understand the systems recharge capabilities and the overload capacities.

References

Jungreis, A.M., Abb Power T&D Company Inc., 2001. Uninterruptible power supply. U.S. Patent 6,184,593.

King, A. and Knight, W., 2002. Uninterruptible Power Supplies. McGraw-Hill Pub..

Nayar, C.V., Ashari, M. and Keerthipala, W.W.L., 2000. A grid-interactive photovoltaic uninterruptible power supply system using battery storage and a back up diesel generator. IEEE Transactions on Energy Conversion, 15(3), pp.348-353.

Welches, R., Hohm, D., Wen, J., LeRow, K. and Griessel, R., Welches Richard Shaun, Hohm Daniel P. and Lerow Kevin E., 2003. Hybrid variable speed generator/uninterruptible power supply power converter. U.S. Patent Application 10/691,357.