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Glossary of Power Terms
Information for this page provided by Exide Electronics, Raleigh, North Carolina.
Blackout A zero voltage condition lasting for more than two cycles. Same as a power failure.
Brownout A steady state RMS voltage under nominal by a relatively constant percentage.
Critical Load Devices and equipment whose failure to operate satisfactorily jeopardizes the health or safety or personnel and/or results in loss of function, financial loss, or damage to property deemed critical by the user.
Cycle A complete AC waveform. See figure below.
Electrical Line Noise Radio Frequency Interference (RFI) and Electromagnetic Interference (EMI) are unwanted electrical signals that produce undesirable effects in sensitive electronic equipment.
Frequency The repetition of cycles measure in Hz. 60 Hz is the standard frequency in the U.S. 50 Hz is the standard frequency in other parts of the world. 60 Hz = 60 cycles per second.
Frequency Variation A change in frequency of more than 3 Hz.
High Voltage Spike Rapid voltage peak up to 6,000 volts with a duration of 100mS to 1/2 cycle.
Hybrid UPS Combination of on-line UPS and off-line UPS features. A hybrid UPS has improved performance compared to an off-line UPS, but lacks the higher performance factors of an on-line UPS. It is commonly called line-interactive or ferroresonant, depending on the technology used.
Microsecond 1,000,000th of a second (mS).
Power Sag Voltage below 80% to 85% of rated RMS voltage for one or more cycles.
Power Surge Voltage above 110% of rated RMS voltage for one or more cycles.
RMS Voltage The range of usable voltage + or - 170 VAC.
Switching Transients Rapid voltage peak up to 20,000 volts with a duration of 10mS to 100mS.
 

 

PROBLEM DEFINITION VISUAL CAUSE EFFECT SOLUTION
         
no protection
limited protection
unlimited protection
power surges

Voltage above 110% of rated RMS voltage for one or more cycles

 Heavy electrical equipment being turned off. Memory loss, data errors, flickering lights, equipment shutoff.
Surge Protector
Line Conditioner
Standy battery UPS
Line interactive UPS
On-line UPS
high voltage spikes Rapid voltage peak up to 6,000 volts with a duration of 100mS to 1/2 cycle Lighning strikes, switching operations, arcing faults, static discharge. Loss of data, burned circuit boards.
Surge Protector
Line Conditioner
Standy battery UPS
Line interactive UPS
On-line UPS
switching transients Rapid voltage peak up to 20,000 volts with a duration of 10mS to 100mS. Lightning strikes, switching operations, arcing faults, static discharge. Memory loss, data error, data loss, component stress.
Surge Protector
Line Conditioner
Standby battery UPS
Line interactive UPS
On-line UPS
power sags Voltage below 80% to 85% of rated RMS voltage for one or more cycles. Heavy equipment being turned on, starting large electrical motors, switching power mains (internal or utility). Memory loss, data errors, flickering lights, equipment shutoff.
Surge Protector
Line Conditioner
Standby battery UPS
Line interactive UPS
On-line UPS
electrical line noise Radio Frequency Interference (RFI) and Electromagnetic Interference (EMI) and other frequency causes. Data error, data loss, keyboard lockup, storage loss; system lockup. Data error, data loss, keyboard lockup, storage loss, system lockup.
Surge Protector
Line Conditioner
Standby battery UPS
Line interactive UPS
On-line UPS
frequency variation A change in frequency of more than 3 Hz. Erratic operation of emergency power generators, unstable frequency power sources. Disk crash, keyboard lockup, program failures, data corruption.
Surge Protector
Line Conditioner
Standby battery UPS
Line interactive UPS
On-line UPS
brownout A steady state of RMS voltage under nominal by a relatively constant percentage. Heavy equipment being turned on, starting large electrical motors, switching power mains (internal or utility), overloaded circuits. Premature hardware failure, data loss and corruption.
Surge Protector
Line Conditioner
Standby battery UPS
Line interactive UPS
On-line UPS
power failure A zero-voltage condition lasting for more than two cycles. Circuit breaker tripped, power distribution failure, utility power failure. File corruption, hardware damage, data loss and corruption.
Surge Protector
Line Conditioner
Standby battery UPS
Line interactive UPS
On-line UPS