To UPS or not to UPS?

To UPS or not to UPS?

You can buy a cheap UPS, but like anything else in life, you get what you pay for.

Here is what to look out for:

1. VA Rating
The required VA Rating depends 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) with the mains voltage (normally 220V), and divide by the PF (Power Factor) of the equipment. The PF of computer and laser equipment is normally 0.6 

So, if you are running a small CO2 laser (PLT-3040 / PLT-6040) and a (plugged into mains) notebook off your UPS, you will use say 3 Amps at maximum. If your mains Voltage is 220V and the PF is 0.6, you can calculate – 

3A x 220V = 660W / 0.6 PF = 1100VA.

A 1200VA UPS will just cover this, but for future expansion or additional equipment (say an internet router for example) and to not stress the UPS by running at maximum load all the time, you should add at least 20% capacity. Therefore a 1500VA UPS (1.5KVA) – or larger – should be considered.

If more computers or larger lasers are used, add all the Amps together and do the calculation. So, if you are running a medium CO2 laser (PLT-6040HQ / PLT-960HQ / PLT-1390) and a (plugged into mains) notebook along with a desktop PC off your UPS, you will use say 4 Amps at maximum. If your mains Voltage is 220V and the PF is 0.6, you can calculate – 

4A x 220V = 880W / 0.6 PF = 1467VA.

A 1500VA UPS will just cover this, but for future expansion or additional equipment (say an internet router for example) and to not stress the UPS by running at maximum load all the time, you should add at least 20% capacity. Therefore a 2000VA UPS (2KVA) – or larger – should be considered.

2. Backup Running Time

The Backup Running Time will be proportional to the load that is connected to the UPS. The higher the load, the less the Backup Running Time. You can have a Backup Running Time of as little as 2 minutes (which will allow you to shut down the equipment connected to the UPS before the power fails), or many hours of Backup Running Time so you can keep your equipment running until mains power returns.

A longer Backup Running Time and higher protection levels obviously costs more than short Backup Running Times and lower protection levels.

3. UPS Types and Protection

The level of protection you want will determine which of these is most suited to your needs. 

The main UPS types are:

a) Off-Line Modified Sinewave

Equipment runs off the mains via a limited AC filter under normal conditions. When the power fails, this type of UPS system switches over to a simple inverter to provide mains-like power for a short time to allow you to shut down the equipment. The backup time is normally short and will depend on the VA rating (see definition above) of the UPS and the amount of power your equipment draws from it. This type of UPS will give you very limited or no protection against power surges or spikes. Typical backup time is around 3 – 10 minutes. Mostly, the backup time can't be extended. This type of system is aimed at the SOHO market and is mainly used when you have repeated, short power failures (load shedding) but a reasonably good mains supply. Not recommended for critical applications or areas where there is bad or high fluctuating mains supply.

Cost: Low
Power Level: About 600VA to 1200VA
Protection level: 0 – 10%

b) Line Interactive Pure Sinewave

This type of system will provide a bit more time to save work and shut down your equipment after a power failure and is also designed to regulate the output voltage and prevent (mostly) spikes and surges from reaching sensitive equipment (computers, internet routers, printers laser machines etc.).

Backup time will depend on the VA rating of the UPS and the amount of power your equipment draws from it. Typical backup time is around 5 – 15 minutes. Some models can be fitted with additional batteries which can extend the backup time to several hours. Recommended for semi-critical applications and small sized business – IF the UPS output is pure sinewave (line interactive systems are also available in stepped squarewave or modified sinewave).

Cost: Medium
Power level: About 800VA to 3000VA
Protection level: 10 – 50%

c) Online Sinewave

This type of system will provide protection and backup on power failure for critical applications. Your equipment is always running on battery-produced power (which is connected to and charged by the mains) and it is not directly connected to the mains. The pure sinewave output ensures the cleanest, most compatible AC output for computers and any other critical load. Typical backup time is around 5 – 15 minutes. Plug-in external battery packs are available to extend the backup time to several hours. Aimed at the professional and upper business market, this is the recommended solution for laser machines and computers, with the highest protection level available.

Cost: High
Power level: About 800VA to 100KVA (or more with paralleled systems)
Protection level: 100%

UPS systems are not designed to be located outside. They should be indoors in a relatively cool area and low humidity (less than 65%). The life span of the batteries will be greatly reduced in warmer areas.

Standard UPS batteries are normally either sealed maintenance free, or semi-sealed maintenance free, and have a useable life of 3 – 5 years. Long life batteries (8 -10 years useable life) are also available – but significantly more expensive.