Alternate Definition: UPS is an electronic device that provides emergency power to a load when the input / main power fails.
Explanation: A complete UPS system consist of 1.) Rectifier or converter that converts Alternating Current (AC) to Direct Current (DC) to charges the battery, 2.) Battery and 3.) Inverter, this inverter converts the 12 / 24 Volts DC from battery to 110 / 220 Volts AC.
There are two basic types UPS:
- Stand-by UPS
- On-line UPS
What are Stand-By UPS ?
Stand-by UPS are such systems which are connected to the load through a STS (static Transfer Switch). When main supply is live, the voltage from main supply is used to charge the battery and main supply is directly connected to the load. (as shown in the diagram below)
When main power fails, (or in case of WAPDA electricity load shedding) the static transfer switch shifts the connected load on UPS system. STS operates in milliseconds.
The Rectifier Unit converts the main AC supply into DC voltage (Usually 12 Volts DC), which are used to re-charge the batteries.
The Filter circuit & Regulator circuit are used to filter and regulates the DC voltage for smooth charging of battery.
The Inverter Unit converts back the DC voltages, coming from battery, into AC. The Oscillator circuit generates the desired frequency (usually 50 Hertz) and then supply to load through Static Transfer Switch.
Static Transfer Switch: The main operation of Stand-by UPS depends upon STS. Static Transfer Switch is also known as relay. STS allows switching from main supply (WAPDA) to UPS Supply. In normal condition sts connects the main supply directly to the load, during and breakdown or power failure in main supply it shifts the load to the UPS without any interuption because it operates in milliseconds. When the main supply COMES BACK sts shifts back the load on main supply. Power Plant TC 263
What are On-Line UPS ?
On-live ups, also called Continuously Delay UPS, are always connected in series between the load and the source. It consist of Rectifier, Battery and Inverter.
Rectifier is used to to convert the AC voltage into DC to re-charge the battery. The battery is used to store back up energy. The inverter is used to invert back the DC, coming from battery, to AC according to desired or rating voltage of load.
Importance and Uses of UPS:
- In homes as Back-Up power ic case of electricity load shedding.
- It is used as emergency Power.
- Used in Hospitals for backup energy and emergency.
- In telecommunication Exchanges.
- Used in stadiums for score counting & lightning.
- CNG stations and Petrol Pumps for cash management and calculations.
- In Computer systems, Software production and Data Banks.
- Used in Industry.
- Security Systems.
- Home Appliances.
- Radio & TV Broadcasting.
- Power Stations, Grid Stations, Control Systems.
The Installation and Connection of UPS is very simple. The diagram below explains the Installation and Connections.
UPS Wiring Picture: (Battery and AC Wiring)