Reply To: QU-32 and UPS

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Just for reference: Uninterruptible power supply

Let me throw in some numbers. We all know that our mains carry AC, a somewhat sinusoidal waveform with 50/60Hz, so we have regular mini-brownouts each 20 resp. 16mSec which are totally uncritical, since any powersupply contains a rectifier and capacitors to hold internal voltages at least for this period. So switching time of 10mSec is not even recognized by any connected device. Normally a powersupply should be able to compensate a couple of missing phases (~100mSec) without affecting system operation.

The 10mSec relate to isolating your devices from mains in case of large transients on the mains input which may lead to damage. Offline and Line-Interactive UPS therefore can not provide 100% safety. The much more expensive online UPS source power from batteries only and the load is never directly connected to mains.