Must know before buying a UPS
By Ravindra Johari
Dec 28, 2016
Everyone desires Power, ask the Designers. They are not behind Power, they design it instead. Let's get started.
1. Appliances on UPS.
The first thing to decide before selecting a UPS are the appliances and devices that would be on UPS under Power off conditions.
The summation of the number of devices and the maximum Power consumption of each device would give the minimum amount of
Power Output that the UPS needs to supply under Power off conditions, along with the number of Sockets that can suffice
the Power requirement for multiple connected devices. It's important to understand the concept of True Power in Watts and Apparent Power in Volt Amperes(VA) and the ratio of the two called Power Factor. We'll not get into how and why True Power is always less than the Apparent Power and the difference between impedence and resistance. But the industry defacto is True Power delivered to the appliance is 60% of the Apparent Power that the UPS can deliver. This along with the amount of time that the UPS needs to supply power can provide a value of the Overall Wattage requirements from the Battery inside the UPS or connected externally to the UPS.
This coupled with the type of wave the UPS is spec'd - True Sine Wave, Approximation to a sine Wave or Simulated Sine wave. Sensitive appliances and equipments should consider only
a Pure Sine wave UPS. Many devices don't bother with the qualilty of AC provided by the UPS, a good appliance design would cope up with any type of AC power supplied. However there are devices that wouldn't cope up with the bad input Power and you need a True Sine Wave UPS.
Various LED indicators provide indications about the status of the UPS and if any action is required by the user.
- Online Indicator : The UPS is in the bypass mode and the devices are connected to the mains.
- On Battery : The UPS is providing power to the connected devices. usually this is accompanied by a beep sound every few seconds.
- Overload : the battery in the UPS is not able to provide sufficient power that the load demands.
Other indicators like UPS Fault and Battery replacement would call for servicing by the manufacturer personnel.
3. Alarms: Like indicators provide visual indications, Alarms beep on account of certain conditions.
- On Battery : Power is provided by the UPS when the mains is powered off.
- Low Battery : Battery is at it's threshold supplying current and needs a recharge for further UPS operation.
- Overload : The load draws more current than the battery is specified at. Either a higher Power UPS is to be considered or disconnect appliances from output as feasible.
- Over Heat : The work done by the UPS has increased it's temperature beyond specified limits and needs to cool off.
- UPS Fault : There is wiring fault like reversed polarity or ground wire missing etc.
4. ROHS Complaint UPS.
Restriction of Hazardous Substances compliant UPS parts exclude specific substances like Mercury, Cadmium, Lead, Hexavalent Chromium etc that cause harm to human body. ROHS is a directive that has become a law in most of the European contries following safety standards.
5. UPS with Internal or External Battery.
Most UPS for IT devices at home like Router, Desktop, Laptop, Wifi Modem would suffice with a UPS with Internal battery. This battery would usually be of 12 Volts
supplying current as the specified VA levels.
For other electrical appliances like Microwaves, Heaters, ACs, Refrigators UPS with external batteries needs to be considered. These batteries demand a simple connection with the UPS and are
also of 12 Volts output with different AH levels and can be connected serially to increase the overall Voltage Ampere Hours to meet specific time requirements.