Learn about Power flow, Sags, Dips, Phase rotation, Harmonics, Flicker and more!
CBEMA – Computer Business Equipment Manufacturer’s Association adopted curve IEEE Standard 446 (orange book) curve. Recommended Practice for Emergency and Standby power systems for Industrial and Commercial Application.”
- Wave form Sine wave THD (total harmonic distortion) maximum 5%.
- 3 Phase system phase imbalance of voltage 3% – 6%.
- Frequency stability 60 +/- 0.5Hz.
- Output Voltage +6% Max. -13% Min. from Nominal Value.
- Voltage can fall to 0V but should recover in 0.5 Cycles.
- On turn on Voltage should reach steady state within two seconds.
- Upto 200% over Nominal Voltage should be tolerated for 100uS. ( Transients, spikes and Inductive Kickbacks come in this)
- Upto 30% over Nominal Voltage should be tolerated for 0.5S.
ANSI – American National Standards Institute
“Standard Voltage Ratings for Electrical power systems & Equipment”
- Steady State Variations +/- 5% of Nominal Voltage. T
- Three Phase Voltage Imbalance 5% Max..
- Standard Frequency 60Hz.
- Frequency 60Hz Hz is Hertz.
- One Cycle = 20mS (milliseconds) one full sine wave.
- Max – Maximum
- Min – Minimum
- uS – micro seconds, S – seconds.
Cause of Transients
- Switching Loads Simultaneously (inductive loads).
- Power factor correction capacitors and devices.
- Lightning strikes (enhanced by earth faults).
- Line Inductance (inductive kickback, resonance).
- DC and AC Drives for Motors.
- Rectifiers with large filters and stray inductance.
The CBEMA guideline, created by the Computer Business Equipment Manufacturers Association is a realistic, at-the-equipment, maximum allowable voltage that equipment can withstand, without damage or upset.