Power Conditioning Equipment

Let's understand different power conditioning UPS systems and how to choose the right one to safeguard your IT infrastructure against power problems

Friday, September 05, 2008

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In countries like India power conditioning equipment plays an important part in reducing downtime. It provides protection against common power disturbances and power outages. The most commonly used PCE is UPS. Let's start with the commonly available types of UPS and other PCE devices and what you should look for when buying them.

Line Interactive UPS
Such UPS are meant for small data centers and businesses. In these, the UPS inverter is continuously connected to the output, which allows the UPS to provide additional filtering. When buying such UPS always look for one with a tap-changing transformer. Such transformers provide voltage regulation by modifying transformer taps in case there is a variation in input voltage. Also look for Line interactive UPS which allow direct flow of AC input to output, in case of inverter failure.

On-Line UPS
Also known as Double Conversion Online UPS, these systems are largely meant for mission critical equipment, data centers, etc. Such UPS use double conversion technology to convert AC power to DC power. Here, the primary power source are batteries of the UPS and the utility power is considered as secondary power source. Simply put, the load connected to the on-line UPS always runs on batteries regardless of whether there's a power failure or not. Due to this, there is zero switchover time when a power failure occurs. Power is directly passed through its inverter and the UPS uses a small part of this power to recharge its batteries and conditions the rest of the power to deliver a nearly ideal output. Another type of online UPS is Delta Conversion On-Line UPS. These are similar to double conversion on-line UPS as they also have inverter as their main power path. Also an added delta converter also supplies power to inverter output. Usually, the size of such UPS ranges from 5KVA to 1.6MW. They have a delta converter which controls i/p power and ensures that power is drawn sinusoidally. With i/p power control, such UPS are also compatible with generators.

Fly Wheel UPS
With Green IT being the latest buzzword, Flywheel UPS are in demand. Such UPS are not new but have significantly improved in the past few years and are mostly used by companies as a first line of defense. This is largely because they provide backup for a relatively short term and are mainly used in conjunction with generators. Instead of batteries these systems store kinetic energy which is converted to electricity. Here again different vendors use different technologies but largely power from the grid is used to rotate the flywheel (which is basically a rotor in a low-friction environment). This rotor's inertia allows it to rotate in case of a power fluctuation and kinetic energy generated through spinning of the rotor is converted to electricity by a small generator inside the UPS. Now the catch is this back up is going to be around 15 seconds or so. Within 15 seconds the main generator should get on to ensure that equipment continues to receive power. Another advantage of a Flywheel UPS is that it uses less space as compared to a static UPS (which needs more space to keep batteries). Sometimes, flywheel UPS are also used in parallel with batteries to improve lifetime and reliability, by reducing recharge cycles of batteries caused by a short power outage.

Conditioning and distribution systems
Other than UPS, power conditioning and distribution systems are also used to protect equipment from power disturbances. These devices are mostly meant for large data centers and designed to optimize power. They also support features like power monitoring, computer-grade power protection and power isolation. Most of these systems are deployed to manage power coming from UPS and ensure that conditioned power is delivered to every equipment. Some vendors claim that these devices can maintain consistent output from +40% over voltage to -40% under voltage.

Final words
When buying PCE always look for one which comes with a dual mains input. This provides enhanced availability by allowing the device to receive power from two different sources, ie if one power source fails, the device can still continue to function by receiving power from the second source. Another good feature is battery modules connected in parallel. This gives the comfort of HA as redundant batteries are available. Similarly, make sure that batteries are hot-swappable so the equipment receives continuous power supply. Also check for generator compatibility; this would ensure that if your batteries run out of steam and you need to run your equipment through generator power, the UPS can be connected to a generator to ensure uninterrupted power. A good PCE should protect against common power problems such as surges, sags, outages, flickers and spikes. When buying PCE, also consider how much input voltage is required by the transformer and output voltage of the transformer. You will also need to consider its KVA capacity, operating frequency, overload capability, time response, etc. Other things to look for are remote management of UPS, battery failure notification through alarms and email etc. Besides deploying power conditioning equipment, it is important to maintain them continuously, so that it continues to keep all other systems running. You need to determine how frequently maintenance should be performed and what kind of running costs to expect. Also, you need to monitor your power conditioning equipment to ensure that it's always up and running. In case something goes wrong, it tells you, in advance, of the same. Also, it's always better to ask vendors and other customers about what kind of failures to expect and how to tackle them before buying a power conditioning equipment.

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