Common power problems.
There are various common power problems that UPSs are used to correct. Here are some examples and the damage they might cause:
- Power failure — Total loss of utility power. Causes electrical equipment to stop working.
- Voltage sag — Transient (short term) under-voltage. Causes flickering of lights.
- Voltage spike — Transient (short term) over-voltage, i.e., spike or peak. Causes wear or acute damage to electronic equipment.
- Under-voltage (brownout) — Low line voltage for an extended period of time. Causes overheating in motors.
- Over-voltage — Increased voltage for an extended period of time. Causes light bulbs to fail.
- Line noise — Distortions superimposed on the power waveform. Causes electromagnetic interference.
- Frequency variation — Deviation from the nominal frequency (50 or 60 Hz). Causes motors to increase or decrease speed and line-driven clocks and timing devices to gain or lose time.
- Switching transient — Instantaneous undervoltage (notch) in the range of nanoseconds. May cause erratic behavior in some equipment, memory loss, data error, data loss and component stress.
- Harmonic distortion — Multiples of power frequency superimposed on the power waveform. Causes excess heating in wiring and fuses.
An uninterruptible power supply (UPS), also known as an uninterruptible power source or a battery backup, is a device that maintains a continuous supply of electric power to connected equipment by supplying power from a separate source when utility power is not available.
Types of UPSs
- Standby — UPSs of this category pass the current during normal operation directly from the input to the output. Switching to battery operation takes up to 10 milliseconds. They only protect from power failures.
- Line Interactive — They protect not only from power failure, but also from underand over-voltage. They are ideal for small to enterprise IT and network environments.
- Double Conversion — These UPSs offer protection from all power problems. Suitable for mission-critical applications, server farms, hospitals, etc.