Line Interactive UPS Operation
[Single Phase only 220V in 220V out]
Line interactive UPS has 4 basic sections
1) Battery Charger
2) Batteries
3) Inverter [Changes battery voltage to 220volts]
4) Regulator [AVR]
When mains [220volts from Eskom] is present the load [computer etc] is fed via a regulator that compensates for any fluctuations in the incoming [Eskom] voltage. The inverter is off. When Eskom fails [power failure] the batteries connect to the inverter via a switch which produces 220volts to feed the load. The batteries run the inverter for approximately 15 minutes.
Due to the cost effective nature of their manufacture, this type of UPS cannot run for a long period of time.
It does however; give sufficient time to shut the computer down either manually or via shutdown software if this is installed.
This type of UPS is ideally suited for a stand alone PC.
Online Double Conversion Single Phase UPS
[220volts Input, 220volts Outputs]
An Online UPS has three basic sections
1) Battery charger
2) Batteries
3) Inverter
When mains [220volts from Eskom] is present, this feeds the battery charger which in turn charges the batteries. The batteries constantly power the inverter which powers the load [computer etc]. The inverter also regulates [keep constant] the voltage to the load. When the main fails, the batteries simply keep the inverter running until they go flat.
There is no switching the inverter on and off and the regulation is excellent.
Because the inverter runs continuously, with suitable batteries and battery charger back up times on a power failure can exceed 12 hours.
Single phase means the input is 220volts and the output is 220volts.
This range of UPS goes from 1kva [1000va] to 15kva [15000va].
Online Double Conversion three phase UPS
These UPS systems basically operate in the same way as the online single phase UPS systems.
Three phase UPS systems can be broken down into two categories
1) Three phase input [380volts] single phase output [220volts].
The sizes here usually start at 10kva and go up 30kva.
2) Three phase input [380volts] three phase output [380volts].
The sizes here are from 40kva to 100kva and larger.
Parallel Redundant Double Conversion UPS
This type of UPS system is where two or three UPS's inputs are joined together and their outputs are joined together.
This configuration of similar size UPS's gives two options.
1) The power available to the output is the sum of UPS1 plus UPS2.
i.e. if both UPS's are 6Kva, they will run a 12Kva load.
A third UPS can also be added, should the load increase.
The maximum load is now 18Kva.
This is a very cost effective way of growing your UPS
power requirement.
2) Should one UPS fail the other UPS will carry the full load.
This is an excellent option to backup critical equipment.
Power Management and Shutdown Software
This software, which is supplied with the UPS, is loaded onto a computer that is connected to the UPS via a RS232 cable. This software performs two main functions.
a) Power Management
Power outages, dips, surges etc are logged so that a systems
administrator can see the quality of the power.
b) Should the computer be unmanned and there is a power failure, after
a pre programmed time the software will initiate an orderly shutdown
of the computer.
SNMP Adaptors
[Simple Network Management Protocol]
This adaptor interfaces between the UPS and a computer network.
The UPS can thus be seen by the whole network and not just the PC connected to the unit.
Definition of a Double Conversion UPS
Eskom [AC] voltage enters the UPS and feeds a battery charger. The battery charger changes the AC to DC to charge batteries. The DC from the batteries feeds an inverter. The inverter changes the DC to AC which feeds the load [computers etc].
It can thus be seen that there were two changes in the voltage [AC TO DC and DC to AC]. This is a double conversion.
All Alpha Power UPS systems use the double conversion principle as we believe this to produce far better regulation and isolation than a single conversion UPS system.
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