How UPS systems work for critical power supplies?
In this article we will discuss how UPS systems work for critical power supplies in theory versus reality.
UPS systems work as an instantaneous emergency backup. Electrical power source usually consisting of lead acid batteries. For larger systems it can be a Rotary Fly Wheel UPS system. Supporting power electronics converts incoming AC to DC output current. Above all supporting critical power load.
UPS systems provide instantaneous No BREAK power to the downstream load from 1 minute up to 15 minutes during which its stored electrical power will be provided until the GRID power is reinstitute.
In True Online double conversion UPS, the electrical power is released from the batteries. Whereas a Rotary Fly Wheel system stores its energy kinetically within the flywheel. Both of these UPS systems are used for critical power supplies.
For NON critical loads it is common to use cheap line interactive UPS that ‘spring to life in micro seconds’ when the UPS sees no GRID power. All Line interactive UPS do have a micro break in power before provided their stored power, hence this is ‘break before make’ power and never used for critical power supplies.
IT loads. Data Centres, Hospitals, Banks all use UPS systems that are either Double Conversion Uninterruptible power supply ( UPS) systems or Rotary Fly Wheel Systems.
How UPS systems work in reality?
In the event of a power outage or power drop the UPS will release its stored electrical power to the load and provide the missing power.
All UPS systems synchronize the output frequency with the input by means of built in Automatic voltage regulators (AVRs), although we must state that ALL the low cost line interactive UPS don’t have the same robust provisions as the more expensive True Online or Fly Wheel systems.
If you want real NO Break power protection then don’t install a line interactive UPS
Ensuring your load has both Uninterruptible power and continuous power, any UPS must be backed by a generator. (Genset)
Every Generator also has an automatic voltage regulator (AVR) to keep the output power at 50hz. Should the power fluctuate, it is the AVR that keeps the output power between 49.5 and 50hz.
This range of 49.5hz to 50hz needs to be maintained to ensure your load doesn’t lose power even if your emergency power system is still providing electrical power.
Frequency is important.
An automatic voltage regulator (AVR) keeps the output power frequency at 50hz and no lower than 49.5 hz.
Should the frequency drop out of this range, your emergency power from the UPS and Generator will drop the load thus lose power.
Replace batteries BEFORE they fail.
Keep your generator fuelled.
Ensure regular service & maintenance regimes are in place for both your Uninterruptible power supply (UPS) systems and back up generators to prevent loss of frequency/power.
For design, equipment and installation of uninterruptible power.
Here’s another article to consider UPS Power Systems Failure & How To Prevent Them
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