5 UPS Topologies – Line Interactive Runs on AC power from Utility and switches to Inverter if Utility source power quality is not within predetermined tolerance. Provides some surge protection.Benefits – very efficient due to minimizing inverter run timeDisadvantages – limited surge protectionApplication – Single computer or single rack
7 Delta ConversionThis Line Interactive system carries the load by using both the utility line by means of a Line Conditioner (Course Regulation) and two converters (Actually two inverters for Fine Regulation & Battery Charger).This topology can regulate the load voltage by manipulating the secondary winding of the series t-former using the Series Converter.AdvantagesSystem does not go on battery for voltage fluctuations.System efficiency is higher in normal mode.DisadvantagesThe unit needs two inverters, less reliability.It circulates more ripple current to the batteries.If the utility frequency goes out of tolerance, the unit must go on batteries.
9 UPS Topologies – Double Conversion Rectifies AC power into DC and then converts the DC back to AC. Provides clean power, completely isolated from the Utility during normal operation.Benefits – No interruption of Power; Protects load from Utility spikes and SurgesDisadvantages – Greater losses than Line Interactive design
11 UPS Design Key Market Drivers Reliability –The 5 “9’s” % up timeEfficiencyEPA InfluenceGreen GridServer TechnologyVoltageOutage Ride Through
12 Efficiency Line Interactive UPS ~98% efficient Double Conversion ~ 92% to 94% efficientMethods to improve UPS efficiencyEliminate Input and Output Transformers“ECO” mode -Line interactive mode of operationData Center Efficiency TrendsEliminate PDU transformersElectrical Distribution Voltages
14 Server Technology Server Voltages Today –120VAC - 240VAC 600V or 480V distribution with PDU transformers400V distribution without PDU transformersFuture – 277 VAC? ; 480VAC?Server Power Outage Ride ThroughCEMBA Curve – Now the “ITIC” CurveKey Factor for “ECO” mode.
16 UPS Components Rectifiers SCR or IGBT Inverters IGBT with PWM SCR – 6 Pulse and 12 PulseInvertersIGBT with PWMStatic Switch ModuleTransformersInput TransformerOutput TransformerFiltersInput Harmonic Filters
17 Rectifiers IGBT Rectifier – Clean Input SCR Rectifiers High power sinusoidal rectification – low harmonics, limited need for filtersSCR Rectifiers6 Pulse – ~30% THD without filters – 7% with 5th Harmonic Filter<5% with 5th and 11th filter12 Pulse – reduces harmonics by using parallel rectifiers with a phase shift ahead of one rectifier – requires input transformerLower efficiency than 6 PulseRectifiers can be programmed to sequentially ramp up
18 6 Pulse Current InputTHD without filterTHD with filter
20 750 kVA - 6P vs 12P Rectifier – Energy Efficiency Percentage load6-Pulse - no Xfrmr12-Pulse w/xfrmr25%92.8 %91.8 %50%94.2 %93.3 %75%93.2 %100%93.6 %92.4 %EfficiencyDifference1.0 %0.9 %1.2 %
21 Inverters Converts DC power into AC using IGBTs and PWM Several different methods to implement PWM
22 Static Switch ModulesStatic Switch Module consists of breaker or contactor in series with back to back SCRs.Static Switch modules can be continuous duty or momentary rated. Momentary rated Modules have a breaker or contactor in parallel.Continuous duty is required for ECO mode operation.
24 UPS Output Transformer Isolates load from inverterProvides greater protection to load during inverter failureTransformer MTBF > IGBT MTBF
25 Input Filters 5th Harmonic Cancellation Power Factor Correction The filter is designed to cancel the current distortion that is most present on the 5th harmonic.Power Factor CorrectionThe input filter also raises the input pf to approximately 0.93 with addition of capacitors. This will allow the generator to operate more efficiently delivering more real power
26 Multi-Module UPS Configurations Paralleling UPS ModulesCapacity or RedundancyCentralized BypassDistributed BypassTypical Parallel UPS ConfigurationsIsolated RedundantParallel RedundantDistributed RedundantSystem plus System
27 Parallel for Capacity Parallel for capacity reduces MTBF value Multiple units = NNot recommended for a N System (single system)Frequently used for System + System (N+N)MTBF impactParallel for capacity reduces MTBF valueApproximately half the MTBF of a single unit
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