What type of UPS to use and why it is relevant to AV
I am often asked by Pro AV installers why they should use a UPS and which type to use.
In many cases there is a misconception that UPS systems are to provide enough backup power to let you finish your telepresence meeting or to let you finish watching your Netflix movie when there is a power cut. The primary functions of a UPS are to protect the equipment connected to it from brown outs and black outs and to provide enough power in case of a black out to give the equipment to shut down safely, without data loss or to give enough time for a back-up generator to start up.
The protection of AV equipment in particular is very important as brown outs can cause serious damage to sensitive AV equipment.
Types of UPS Systems
There are 2 basic types of UPS systems line interactive and online-double conversion. There are also Offline systems, but these are not really UPS as it means ‘uninterruptible power supply’ and a power cut with an offline system will cause an interruption.
Below is a brief explanation of the differences.
Standby/Offline battery Back-up
The offline UPS is just a battery, providing limited back up power, sometimes with regulation for brown outs. The cheapest standby/offline units will do only turn on batteries when the power goes out. Some more expensive units may also offer some surge protection. An offline UPS can take up to 45 milliseconds to switch over to battery power. This delay can be enough to cause damage to equipment.
Line Interactive UPS
The line interactive UPS does filter out some peaks in power, but is not fully regulating the output current. Fluctuations in the output current are still passed through. These units will offer a quicker response time (up to 10 milliseconds) and have some basic automatic voltage regulation (AVR) and surge suppression. Lower-priced units will put out a simulated or modified, sine wave and higher-priced units will produce a pure sine wave. Sometimes, these higher end units will go to battery in a brown-out (to boost the voltage) and in an over-voltage situation (to lower or “buck” the voltage).
Since the line interactive ups still has a delay of several milliseconds before the batteries kick in after a power cut, there is still a risk of causing damage to equipment.
Further, and probably most relevant to the Pro AV industry, the Line interactive UPS has only limited ability to filters out fluctuations from the input AC-power. These small fluctuations can be amplified in AV setups (by amplifiers for instance) and manifest itself in ‘unexplained’ noise or snow on screens or in humming noises from speakers. A line interactive UPS for AV, although commonly used, is not advisable.
The highest level of UPS protection is online. Online units take the incoming current (AC), rectify it to the battery voltage of the UPS (DC), filter it, reinvert it and convert it to the appropriate output voltage for the unit (AC). Consequently, The output voltage is always rock-steady and the sine wave is always pure.
None of the small fluctuations are passed by an online UPS. Only clean power out!
Also, there is no delay from power cut to battery power. It is always on the batteries. Further benefit of this is that this is better for batteries, so you’ll typically get a year or two more lifespan from them over the other types of UPSs.
To learn more of the Niveo Professional UPS systems, please check: http://www.niveoprofessional.com/product-category/power-products/
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