An Uninterruptible Power Supply (UPS) is a battery powered electronic device that continues to supply electricity to the load for a certain period of time during utility power failure or when there are fluctuations in line voltage outside the normal operating limits.Uninterrupted Power Supply (UPS) is being widely used in many countries as a backup electrical power source for homes where there is acute shortage of electricity and frequent power outages is a commonplace.In such areas,UPS serves a good source of backup power for homes to run a few bulbs and fans in event of power outage.As soon as the grid power goes out,UPS automatically starts supplying backup power to those appliances which have been wired to power through UPS.The amount of charge stored in battery connected with UPS depends upon the power rating of UPS in KVA,its Charging Current and storage capacity of the battery in Ah (Ampere Hour).
Typical application of a UPS to serve as a PC backup power source.Large and permanently wired device may be used to supply backup power to entire home,servers or other equipment.
When you need to choose your backup power source,the main things to decide are :
Typical application of a UPS to serve as a PC backup power source.Large and permanently wired device may be used to supply backup power to entire home,servers or other equipment.
When you need to choose your backup power source,the main things to decide are :
- The amount of electrical power you may need during blackout when grid power is down.
- The length of time for which you need backup power.
- Your budget.
- Topology or Internal Design of UPS that dictates how UPS will operate in various environments.
To choose your backup power source,you need to properly size your system.While sizing your system,you need to add 10-20 percent margin for system derating and prevention of false tripping of its circuit breaker.Note, since many appliances have surge current exceeding their steady state current, you need to make sure your backup system has sufficient surge capacity to accommodate all the loads at start up. This is especially important for automatic home generators. If you choose a manually activated system, you can always turn off your loads before starting the backup source and then turn them back on sequentially.Home Battery Backup is suitable only for short term outages. A battery needs a source of electricity to recharge.
Derating is a technique usually employed in electrical power and electronic devices,wherein the devices are operated at less than their maximum rated power dissipation,taking into account the case/body temperature, the ambient temperature and the type of cooling mechanism used.
Standby UPS (SPS) : It includes a transfer relay.It switches the load to primary battery-powered Inverter when AC is out of range.Typical load transfer time ranges from 2ms to 10ms depending upon the amount of time it takes to detect the lost utility power and turn on the inverter.This leads to momentary disruption in current supply to the load which accounts for the time taken to switch to the battery-powered inverter.That is why in purely technical terms quoting it as uninterruptible is misleading.Today PC includes internal Switching Mode Power Supply Unit (SMS PSU) which supplies certain hold up time or ride through time.Typically SMS PSU of a PC should provide hold up time of at least 16ms at rated load.This hold up time corresponds to one cycle of 60Hz AC input (1/60 = 16.667 x 10^-3).This hold up time is greater than transfer time of UPS so PC is usually remains powered up continuously while transition from mains to UPS.
Standby UPS Inverter operates in standby mode and starts up only when main power source fails so it has highest efficiency (95-98%) and it is very reliable.Above all it is cheapest of all other backup power sources.That's why it is in high demand as a short term backup power source in event of main power outage.
Line Interactive UPS (SPS) : It allows for a faster response to failure than Standby UPS.It is fitted with circuitry to filter out noise and spikes and provides a smooth and regulated AC output voltage by means of a filtering circuitry and tap-changing transformer.In this UPS topology a bi-directional inverter/charger is always connected to the output and utilizes a portion of the AC power to keep the battery fully charged.In event of utility input AC failure the transfer switch disconnects the AC input from utility and the load is fed from the bettery/inverter.The key advantage of this UPS Topology is that the inverter/converter unit is always connected to the output.Its typical efficiency ranges from 90 to 96%.It is the most common design in range from 0.5 to 5KVA as backup power source for Servers and Networks.
Online UPS (SPS) : It includes a transfer relay.It switches the load to primary battery-powered
Standard 220 volt electric power is a pure sine wave, this is what comes out of your normal wall socket and what all electric devices are designed to work optimally with.A sine wave AC Voltage passes through Zero Volts twice per cycle.Not clearly noticeable to a naked human eye,a simple incandescent light bulb connected to utility mains actually flickers 100 to 120 times (for 50 or 60Hz AC) as the AC Voltage crosses zero to change polarity.
Derating is a technique usually employed in electrical power and electronic devices,wherein the devices are operated at less than their maximum rated power dissipation,taking into account the case/body temperature, the ambient temperature and the type of cooling mechanism used.
Derating increases the margin of safety between part design limits and applied stresses, thereby providing extra protection for the part. By applying derating in an electrical or electronic component, its degradation rate is reduced. The reliability and life expectancy are improved.Intuitively, if a component or system is operated under its design limit, it will be more reliable than if it is operated at or above the design limit.
The salient features of UPS & Battery based Backup Power Source are :
- Lowest cost as compared with other home power backup sources.
- Easy to use.
- Not much professional skill is required for installation.
- Emergency Power is supplied only to the devices that are plugged into the UPS.
- Powers critical appliances via extension cords. May be permanently connected to the house wiring via a transfer switch
- Typical power for residential use: 5-10 kW
- Auto start systems have response time 16-36 ms
- No maintenance required
- Quiet
- May be installed indoor
- Low power consumption at no load (consumes power according to the actual load demand)
- Limited run time (typically 2 to 12 hours) depending on the battery tank capacity
- Look for a sealed deep cycle battery and a temperature compensated charger with a trickle mode to avoid battery overheating
- Standby or Offline UPS
- Line - Interactive UPS
- Online UPS
Standby UPS (SPS) : It includes a transfer relay.It switches the load to primary battery-powered Inverter when AC is out of range.Typical load transfer time ranges from 2ms to 10ms depending upon the amount of time it takes to detect the lost utility power and turn on the inverter.This leads to momentary disruption in current supply to the load which accounts for the time taken to switch to the battery-powered inverter.That is why in purely technical terms quoting it as uninterruptible is misleading.Today PC includes internal Switching Mode Power Supply Unit (SMS PSU) which supplies certain hold up time or ride through time.Typically SMS PSU of a PC should provide hold up time of at least 16ms at rated load.This hold up time corresponds to one cycle of 60Hz AC input (1/60 = 16.667 x 10^-3).This hold up time is greater than transfer time of UPS so PC is usually remains powered up continuously while transition from mains to UPS.
Standby UPS Inverter operates in standby mode and starts up only when main power source fails so it has highest efficiency (95-98%) and it is very reliable.Above all it is cheapest of all other backup power sources.That's why it is in high demand as a short term backup power source in event of main power outage.
Line Interactive UPS (SPS) : It allows for a faster response to failure than Standby UPS.It is fitted with circuitry to filter out noise and spikes and provides a smooth and regulated AC output voltage by means of a filtering circuitry and tap-changing transformer.In this UPS topology a bi-directional inverter/charger is always connected to the output and utilizes a portion of the AC power to keep the battery fully charged.In event of utility input AC failure the transfer switch disconnects the AC input from utility and the load is fed from the bettery/inverter.The key advantage of this UPS Topology is that the inverter/converter unit is always connected to the output.Its typical efficiency ranges from 90 to 96%.It is the most common design in range from 0.5 to 5KVA as backup power source for Servers and Networks.
Online UPS (SPS) : It includes a transfer relay.It switches the load to primary battery-powered
Standard 220 volt electric power is a pure sine wave, this is what comes out of your normal wall socket and what all electric devices are designed to work optimally with.A sine wave AC Voltage passes through Zero Volts twice per cycle.Not clearly noticeable to a naked human eye,a simple incandescent light bulb connected to utility mains actually flickers 100 to 120 times (for 50 or 60Hz AC) as the AC Voltage crosses zero to change polarity.
