When managing emergency back-up power, there are several complicated systems that need to be looked at. These systems need specific attention to the parts, the efficiency, and the quality of their output.
Here is some basic guidance on UPS systems.
Not All UPS Systems Are Made Equally
To fully understand UPS systems, it helps to know the types of UPS units there are and how they work. There are three in total:
- Standby UPS
- Double Conversion UPS
- And line interactive UPS
This UPS is a break/fix type. This system normally has:
- A battery that provides a short-term source of power
- A rectifier or charger to maintain the voltage of the battery
- An inverter to provide power and load during regular operation
- And a static switch to transfer load automatically between utility and the inverter
This UPS could also contain:
- Input and output isolation transformers and filters
- Control circuits, sensors, and monitors
What this system does is converts AC to DC power that is compatible with battery voltage and characteristics.
Double Conversion UPS
There are a few distinguishing differences with this UPS. The first is the primary power path. It goes through the inverter versus the AC mains. This is the one system where input AC doesn’t cause activation of the transfer switch. The reason is simple: the AC is the back-up source. It still converts power from AC to DC, but it then reverts that power back to AC.
The purpose of this is to protect facilities at the highest level as it isolates equipment power from raw utility power.
The unit is also always online. This allows power to be provided with zero transfer time to equipment, making it ideal for facilities with critical equipment or where power conditions are poor.
Beyond this, there is an internal static bypass so that if the UPS has a major failure, critical loads can stay online when repairs or replacements are being made.
Line Interactive UPS
This UPS monitors incoming voltage and provides automatic voltage regulation under low or high voltage conditions. These types of UPSes are designed to preserve the battery life as it might not be necessary to constantly switch between battery mode in places where brownouts occur. Ultimately, they provide protection from power spikes and surges. They also protect batteries from Radio Frequency Interference (RFI) and Electromagnetic Interference (EMI) filtering.
This UPS excels when companies aren’t protecting mission-critical equipment and the utility power being used is clean. These are inexpensive as well, even for smaller offices.
UPS Life Cycle Costs Vary On What’s Bought And How It’s Used
The total cost of UPSes will vary on several factors. Factors that affect the cost of UPS systems are:
- Energy inefficiency – A new UPS system will have a range of 85% to 98% efficiency in true, online mode. However, UPS systems that are underutilized will be enormous energy hogs, providing as low as 40% to 50% efficiency in some older systems.
- Environmental conditions – If the battery is in a dusty or moist area or where there could be a lot of debris, this will affect its performance. Electrical disruptions can also cause issues when it’s not properly assessed.
- Maintenance and design – Companies not providing routine maintenance can shorten the lifespan of the UPS easily. It also inflates costs as companies need to spend more to replace parts. This can be the same case when the design of the system is poor.
- Warranty – Warranty on batteries vary between 1 year and 3 years. It’s smart to go with 3 years and it’s even better if companies can extend initial warranties too which will lower overall costs.
UPSes Protect More Than Power Loss
From the general overview of UPS types, it’s clear that UPSes protect more than just power loss. One other key feature all the UPSes do is provide power conditioning. Power conditioning is where power is being conditioned to protect equipment from power anomalies that would otherwise impact performance.
Power conditioning servers as a buffer to interference and smooths out power fluctuations before being passed through. Power conditioning protects against the following:
- Power failure – where power is totally cut off
- Power sag – short-term low-voltage issues result in stalls or equipment operating slowly.
- Power surges or spikes – short-term high voltage that provides over 110% of normal output and can lead to systems overheating, frying or getting damaged.
- Under-voltage – a condition of brownouts and reduced voltage for a long period of time. Could be a few minutes but can last for a few days. These are more common in the summer when air conditioners are straining the power grid.
- Over-voltage – An increase in voltage for a few minutes to a few days.
- Electrical line noise – high-power frequency wave because of RFI or EMI.
- Frequency variation – loss of stability in normal power supply frequency
- Switching transient – instant under-voltage in the range of nanoseconds
- Harmonic distortion – Distortion of a normal power wave, normally transmitted by unequal loads.
Maintain UPS Systems On A Regular Basis
There are two life cycles to pay attention to. Here is an overview of both.
Static UPS Systems
The average lifespans for three-phase UPS systems is around 15 years. Many systems will need semi-annual or annual maintenance. Do note that battery replacements for VRLA batteries are part of this system and they have their own life spans too which add to the total maintenance cost.
There are normally three regular battery replacements for a static UPS system. These are done on year 4, year 8 and year 12. Replacements for parts can also be affected by the load on the system and reliability.
Flywheel UPS System
The life cycle of this system is about 20 years. Maintenance for this system is done annually but only if the system has no batteries involved. If the system does have batteries, it’s essential to factor in the life cycle of battery replacement.
The bearings on a flywheel UPS system might also need to be replaced every 5 to 8 years. This replacement will require special equipment and a prolonged downtime for the replacement.