February 25, 2013

The Mini UPS inside your server

Many people forget that inside every power supply is a mini UPS.  Its not large but it exists.  It provides the "hold up time" for a power supply and hence your computer.

While this little molecule of power can provide the full load rating of the power supply... it can only do it for 12 milliseconds.

If this little UPS had a battery it would 20,000 times smaller than our standard 12v 7ah battery.  Thats a 12v 0.00004ah battery to you and me.

12 milliseconds isn't alot of time.  Remember, 60 hertz electricity means 60 cycles a second.  Thats 60 cycles per 1000 milliseconds or if my math is right 1 cycle every 16.7 milliseconds.  Or in other words... the mini UPS cant even provide a full sine wave cycle of power.

But you don't need an online UPS system to immediately cover an outage or disruption.  The line interactive UPS units normally switch over to battery power in 3 to 5ms, giving you lots of spare time to make that switch effectively.

But whats even more amazing is that your line interactive UPS can switch back and forth 2-3 times within the span of 1 sine wave cycle.