Design Analysis and Implementation of A 0.5 KVA Uninterruptible Power Stabilizer

This  paper  presents  design  analysis  and  implementation  of  a  0.5  KVA  uninterruptible  electronic power  stabilizer  (UPSz).  Poor  and  instability  of  power  supply  delivery  in  Nigeria  necessitated  the need  for  a  device  that  can  stabilize  voltage,  protect  equipment  from  damages  and  also  provide power  to  the  loads  in  the  absences  of  electricity  from  the  utility  mains.  This  need  motivated  the design  of  a  power  stabilizer  (UPSz).  Method  of  Pulse  with  modulation  (PWM)  was  adopted.  This method  is  capable  of  modulating  a  varying  input  to  a  stabilized  output.  Two  input  sources  were considered;  a  fluctuating  220  V  volt  mains  supply  and  a  constant  12  V  battery.  The  12  V  battery was  rectified  to  provide  an  AC  power  supply  to  the  load  in  the  absence  of  the  utility  mains.  The control  circuit  ensured  a  stabilized  output  voltage  from  input  range  of  140  V  to  260  V  AC  power supply  which  is  about  ±40V  to  the  usual  supply  voltage  from  the  utility  mains  of  180V-220V  in Nigeria.  Appropriate  protection  circuits  were  incorporated  against  surges  to  which  ensured  the safety  of  home/office  appliances.  A  variac  was  used  to  obtain  various  AC  voltage  levels  during  the testing.  The  voltage  and  current  results  at  different  loadings  (in  watts)  of  the  UPSz  were  obtained. These  results  were  compared  with  those  of  commercially  readily  available  offline  UPS  of  the  same rating.  The  UPSz  unlike  the  commercially  available  types  delivered  a  stabilized  voltage  of  220  V  to different  loads  of  60  W  to  400  W  range  at  a  fluctuating  input  voltage  range  of  140  V  to  260  V.  This showed  that  the  designed  UPSz  is  an  improved  and  better  device  than  the  offline  equivalent.  Other