VA RATING :
The UPS VA Rating you require will depend on the load current of the equipment you intend plugging into the UPS. To calculate the VA Rating : multiply the Amps of the equipment (normally indicated on a label on the rear of the equipment or in the technical manual or ask the supplier) you will use with the mains voltage you require and divide by the Power Factor (PF) of the equipment.
SIZING A UPS SYSTEM :
For example : Computer equipment requires : 2 Amps (current) Mains voltage used : 230VAC (AC voltage) Power factor of computer equipment : 0.6 (typical for computer equipment) 2A x 230V = 460W / 0.6 PF = 766 VA You will require a 800VA but to cater for your future expansions and to not stress the UPS by running on 100% load all the time, you always add 20-25% capacity. Therefore a 1000VA UPS (1KVA) should be used in this case. When choosing a UPS system it is a good idea to also plan ahead to cater for expansion so that your investment in a UPS does not outgrow your future needs. If several computers or pieces of equipment are involved, add all the Amps together and do the calculation as shown.
BACKUP TIME :
The backup time is proportional to the load that is connected to the UPS. The more the load, the less the backup time. You can have backup time as little as 5 minutes which will enable you to shutdown the equipment connected to the UPS before the power fails; or many hours of backup time so you can keep your equipment running until mains power returns. Longer backup time and higher protection levels cost more than short backup times and lower protection levels. A UPS system is often used to provide uninterrupted power after mains fail until a generator starts up.
OFF-LINE SQUAREWAVE and MODIFIED SINEWAVE and STANDBY
Your computer is running at standard mains via a small limited AC Filter under normal circumstances (some systems do not have filters at all). After a power failure this type of UPS system switches, via a small relay, over to a simple inverter to provide power to allow you to save your open files and shutdown your computer. This type of UPS System is aimed at the SOHO & small business market and is mainly used when you have repeated, short power failures but a reasonably good mains supply. This type of UPS system is not recommended for critical applications or areas where there is bad or high fluctuating mains supply.
LINE INTERACTIVE STEPPED SQUAREWAVE
Your computer is running at standard mains via a small AC Filter under normal circumstances. After a power failure this type of UPS system switches, via a small relay, over to a simple inverter to provide power to allow you to save your open files and shutdown your computer. The system also normally includes a limited AVR (Automatic voltage regulator) which controls incoming mains fluctuations to a small degree. This type of UPS System is aimed at the SOHO & small business market and is mainly used when you often experience short power failures but a have a reasonably good mains supply. This type of UPS system is not recommended for critical applications.
LINE INTERACTIVE PURE SINEWAVE
This type of UPS system will provide backup to enable you to save your work and shutdown your computer after a power failure and is also designed to regulate the output voltage and prevent, to a large degree, any spike, sags and blackouts from reaching your sensitive equipment (ranging from computers and telecommunications systems to computerised instruments). Recommended for semi-critical applications and small to medium sized businesses. Only recommended for semi-critical applications if the UPS output is pure sinewave (as line interactive UPS systems are also available in stepped squarewave or modified sinewave).
DOUBLE CONVERSION ONLINE SINEWAVE
This type of UPS system will provide total protection and backup on power failure for critical applications. Your computer system is always running on electronically produced power and it is not directly connected to the utility supply. The double conversion, double isolation and the pure sinewave form output ensure the cleanest, most compatible AC output for computers and any other critical load. This type of UPS System is aimed at the professional, medical/industrial and upper business market and is recommended when you have a very dirty, noisy & unreliable mains supply. It is also recommended for all critical Computer and medical applications. This type of system has the highest protection level available.
UPS MONITORING & SHUTDOWN SOFTWARE :
This software is available for many UPS systems. This will enable you to monitor your UPS remotely and in the event of a power failure the software can shutdown the computers connected to the system so that you do not lose any data. DB Space UPS have free shutdown software included. A special SNMP (simple network management protocol) version is also available on request for certain UPS. Will require additional hardware.
UPS ENVIRONMENT & BATTERY LIFE SPAN :
To protect your UPS and its batteries, the system should be placed in the correct environment. UPS systems are not designed to be placed outside where they are exposed to the elements. They should preferably be placed in an air conditioned room but this is not necessary if the environment temperature does not exceed 24 - 26 degrees Celsius. The hotter the environment, the shorter the life span of the batteries. If possible, humidity should also be kept below 60%. Remember a UPS is more complex than the computer that it is driving. UPS batteries are normally semi sealed maintenance free and have a life span of 2 - 3 years. At the end of this time, UPS batteries can be replaced.
systems, especially larger systems, require maintenance. UPS should be tested monthly to ensure that the UPS is functioning correctly. These services help to extend the UPS and battery life span.