Electrical Contracting News (ECN) September 2016 - Page 36

UPS Modularity offers many attractive features. role, other components can be regarded as equally important. One of these is the static switch, which allows the UPS output to be transferred seamlessly between conditioned power and raw mains in response to different threats and failure modes. Below, we look at the static switch and how it contributes to UPS functionality. Figure 1 shows how the static switch connects the critical load to either conditioned power from the UPS or raw mains from the bypass supply. In some installations, the bypass supply could be provided by an on site generator. The static switch has two operational states – ‘On UPS’ and ‘On Bypass’. The static switch typically comprises a pair of inverse parallel connected SCRs linked in series with the bypass and inverter supplies as shown in Fig.2. UPS operational modes The static switch’s role relates to the three operational modes for UPS systems; ‘online’, ‘offline’ and ‘lineinteractive’. Products such as UPSL’s PowerWave 9000DPA can operate in any of these modes. During normal online operation when the mains supply is present, mains power is used to feed the rectifier which generates a stable output DC voltage. This is used both to float charge the battery and supply the inverter. In the absence of the mains supply, the battery takes over and begins to discharge through the inverter which continues to support the critical load with well regulated AC power. This design is often referred to as ‘double-conversion’, due to the two conversion stages, AC- DC and DC-AC. It offers the highest possible level of critical supply integrity because the load is supplied with uninterrupted processed power from the inverter at all times. In addition to the battery’s support during blackouts, the rectifier and inverter protect the critical load from electrical disturbances originating from the mains supply. While the UPS is online, using either mains or battery power, the static switch is in ‘On UPS’ state, connecting the inverter output to the load. However if a UPS fault should develop, causing either the voltage or frequency at the inverter output to exceed acceptable levels, or an overload beyond the UPS’s redundancy capacity appears, the static switch changes over without pow \[\\[ۂ8&Yۈ\\&KۘHHݙ\Y\X\Y܈\؛[\\HXYYY H]X][ٙ\HYXH[\\]][ܛX[\][ۈ۝[Y\˂ݙ\[ Hۛ[H[HݚY\BY\XH][و\X\]K[\\HۙHX[Y[Y܂[]]H[ܚ]X[UY˂]\ٙ[H\][ۈ\XK\XX[HY\H\ۙY[H[BXZ[\x&\]X[]H[۝[Z]Kٙ[H[HYX[]\[ܛX[\][ۈH]X\\]\[&ۈ\\&H[H]HYZ[™Y\XHHH\\\KBXYY\[\\[XZ[\Y™[XH]\H\[[HH[\\\[[XY[XYHۈ[KYH\\\HZ[H]Xœ][[ٙ\HYH[\\]]8$][ $H\܈H\]BL H8$[Y[XZ[\Y\˜\HZ\[]H[YHو[ٙ\B[\\\\YYHH]\K[\Y\]\ܛX[ H]X]]]X]X[H[ٙ\HYX˜\\[HH]\HX\\[H[\\]\[H[Kٙ[K[KZ[\X]H\[\˜\HYH[ܙHYXY[[ۛ[BۙY\][ۜYHYXYXYY\[[\\\[8&ٙ[x&H\Y][Y\œY\Y\8&X[[x&K\]X]\][ۈ[\œ\[[[H[\\[\\›]]܈ܝ\[[ۚ\][ۂ]Y[H\Y\\[\ܝ[]YXX[HY\\\[\ˈ\X[KHXZ[YB\H\]Y[H[HR\\HXK]\\X^HHH\H܈[ۈ]HX\[\]܋X[B[\]ܸ&\]]\]Y[HX[]H\š[\ܝ[YܙH\H]HT\[KYˌNT\ۙ[[]X] ]X]\[[[\B\[\X\H\]BL H]HH[[\K[[\]Hٙ\X[H]X]HX]\\š[Y[X\H[X[]KYXY[B[XY][Y[[K[Y]Z[X[]HYH8&\8&Hۛ[B[[H\X[Y[ \X\[\\H[\[Y[YH\]H[[\[H[HX[ۚ\][ۈ]Y[[H\\[X[ \[HX\\YHۛX[[[[\H۝\]\Y\Yۘ[™܈\]Y[H[ۚ\][ۋY\[˜[\[[ۜˈH\[[[œYۘ[\Yݙ\H۝\XX\[[H[[XۚX[H\\B]ۈ\]Y[H[]]\[]]›ZY\&\[\H][HY\Y[XY]H[[Yۙ][ۜ˂H[[H۝X[^\œXۚ\\ۙHوH\[[\\H8&X\\&H[H\\8&]\&K]\YH8&X\\&H[[H\][B][H[YHH^[[H[HZ[[[[YYX][HZHݙ\\X\\[HܛY\X\\[[H[\ٙ\][K[X\\\X[]H[[Z[]\[B[H[وZ[\K[[\HY][و\[H]Z[X[]K[[H\KH\Yۘ[X[^\™[\\][]X]\\H[B[YH[K][[[\YYBYZ]\HH[\\܈HB]X\\ˈ[\]][K[[[\[H]Y[XZ[[[H\\[Kۘ\[ۂ[\\XHH]HY[T›]\ٙ\H\ ^XH\ۜH™]\H]X][ۈ][X[HX][Z\ܚ]X[Y \H[YH\X]܈[X\XH\]X[]Kݙ\Y؛[\܈][Z[\\][HT[\[\ˈT[[ٙ\^X[]H[Z\\][ۘ[[H8$ۛ[H܈ٙ[H8$\Z]H\]Z\[Y[[[ܚ]Y\وZ\\X[\Y Y][ۘ[K[\T\[\\B[H[KX[[\]X\\\H]HY[[[\[\[Y[][ۜ›ٙ\X[HY[Y\ˈ]\\H[[][ۜ]\H[\[B[ۚ\Y[[ۈX\ٝ[K][[[\Z]\ۈ[\\܈ۈ\\˂H\HوۙH]X]\[[H\™]\Y ]YH[H[وZ[\K^x&\T\XX[HHX\H\]HL H]\B[[\XK\H^XH[X\[B[XH[HX[Z\ܚ]X[YHX[HY\[X]\\ˈ]Xœ]\^HH^HH[\\[\œ\[Y[\ܛX[KYۈ\\“PRSSSBSBTT°\\”\BSH UP°TT°SBHT“QSH BSTTUTBXZ[”\BUPUPQQTYˌ]X]\Z] PLBY\BԌBPLSTT\\œ\BԌԌ‚\\UTBL 0pX[][\\\BԍT›]][[\XH\[\ X\][™\X܈][[\\XH\\Y\ H]X[YYY[XX[ [XۚX[[Y\[[\ݙ\ NYX\&H^\Y[Hو[\[X\][›XY\\][]\[YKX\XX[\[Y\\[Bؘ[[Y\X[ [\X[ [XKY[K[\X\H[YYX[X\]Xܜ˂Y\H Yۈ\\‚͂KL͈T8$T [ ͂L  ̌ M M