عموماً برای ایزولاسیون نول بارهای متصل به UPS از اغتشاشات و نویزهای ولتاژی موجود در شبکه بالادستی می باشد. در متن زیر ترکیب بندیهای 3 و 4 ، گزینه های مورد نظر شما هستند.
UPS configurations and recommended grounding practices
In this case, the bypass source and the UPS source are the same and the bypass circuit has no isolation and is connected directly to UPS output. Thus, the definition of separately derived source is not satisfied. The UPS neutral is not therefore connected to the grounding conductor of equipment or to any local grounding electrode. Since there is no isolation between the source and the loads common-mode noise, attenuation is not ensured (Figure 9.18).
In this case, the bypass supply is through a delta–wye transformer and thus there is galvanic isolation between the input supply to the UPS and the output under all conditions. The UPS can therefore be considered as a separately derived source. The neutral point of the UPS is bonded to the downstream equipment grounding wire as well as to the local grounding electrode. The bypass supply neutral is also bonded to UPS output neutral to provide a return path for neutral currents when bypass circuit is in operation (note that the static bypass switch is in-line wires only and the neutral connection is direct). Common-mode noise performance is better in this circuit if the neutral connection between bypass and UPS is kept short (Figure 9.19).
This configuration shown in Figure 9.20 has a non-isolated bypass but the UPS output is taken to the loads through a distribution center, which incorporates an isolation transformer.
Thus the UPS module is not a separately derived source by itself but the secondary of the isolation transformer is a separately derived source.
Thus the neutral of the UPS module is not bonded to the local bonding conductor.
However, the isolation transformer neutral is bonded to the grounding wire from the computer loads fed by it as well as to the local grounding electrode system.
In this configuration, the power distribution center can be placed as close to the loads as possible so that it gives a better common-mode noise protection compared to the earlier configurations. The isolation transformer can also be used as a step down transformer permitting lower voltage supplies (208/220 V) to be served by UPS modules of higher voltage (380/415/480), which improves the cost-effectiveness of the design for UPS and wiring.
This configuration (Figure 9.21) is similar to configuration 3 except that the service neutral is not brought to the UPS or the bypass module. Thus both UPS module and the distribution center can be treated as separately derived sources and neutral to ground connection is established in both these installations. Noise performance is similar to that of configuration 3.