Page 112 - CITS - Electronic Mechanic - TT - 2024
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ELECTRONICS MECHANIC - CITS




           2  Output frequency depends on the input frequency.
           3  Line interactive UPS has no power factor correction circuit.
           Comparison Between Offline Ups, On-line UPS,Line-interactive UPS

                                            Offline           Line-interactive                     Online
                                                           Typically, large &
            Size                     Compact                                     Typically, small & light
                                                           heavy
            Practical Power Range    0-0.5                 0.5-5                 5-5000
            (kVA)
            Voltage Conditioning     Low                   Design Dependent      High
            Cost per VA              Low                   Medium                Medium
                                     High                  High                  Low-Medium
            Efficiency
                                     (typically 95-98%)    (typically 90-96%)    (typically 80-90%)
            Cost                     Low                   Medium                High
                                                                                 Telecoms; Communications;
                                                           Small and medium
            Typical Application Fields  Homes; Small Offices                     Banking; Transportation;
                                                           businesses
                                                                                 Industrial Environments
           When considering a UPS solution, be aware of the UPS type and corresponding level of protection. The key
           difference among online vs offline vs line-interactive UPS lies in their working principles, which reflects in the
           diversities in their features, functionalities, benefits & limitations. Furthermore, the internal design of the topology
           of a UPS will further affect how it will operate in various application environments.
           UPS Specification:
           Power  factor  (pf)  is  the  difference  between  actual  energy  consumed  (Watts)  and  the  apparent  power  (Volts
           multiplied by Amps) in an AC circuit. It is calculated as a decimal or percentage between 0-1 pf and 0-100% i.e.
           0.9 pF = 90%.
           The nearer the power factor is to unity (1 pf), the closer the two waveforms are in phase with each other, and the
           device uses power more efficiently, hence why power factor relates to UPS efficiency.
























           Convention stipulates that inductive loads are defined as positive reactive power, with capacitive loads defined
           as negative reactive power. But the power factor is never described as positive or negative, it is either lagging or
           leading.
           Lagging Power Factor
           These are loads where the current waveform lags the voltage by a factor equal to the load’s reactance, typically
           between 0.5 and 0.95.
           In the below image, a 2300 VA load with a lagging 0.766 pf would have a real power value of 1762 W (1.76 kW).



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                                    CITS : E & H - Electronics Mechanic - Lesson 56 - 63
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