INTERPRETING THE READINGS: Understanding the. CBEMA Curve. ” Determining Susceptibility”. Throughout the sphere of Power Quality you’ll hear the terms. The ITI, formerly CBEMA, curve was developed by the Information Technology Industry Council of the. United States of America. The curve describes an AC. Abstract: The ITI, formerly CBEMA, curve was developed by the Information Technology Industry Council of the United States of America. The curve describes an.

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It effectively encompasses all the factors involved with voltage deviations, from long term through to high-speed distortions of the waveform. The following other wikis use this file: If the file has been modified from its original state, some details such as the timestamp may not cbeja reflect those of the original file.

The measurements and results can then be analyzed in combination with the CBEMA curve to help understand the nature of power quality disturbances. Low pass filters attenuate frequencies above their cut-off. Basically, the CBEMA curve was originally derived to describe the tolerance of mainframe computer business equipment to the magnitude and duration of voltage variations on the power system. Power Systems Engineering Research Center.

Power Acceptability CurvesStandards.

Told you, Power Quality is an electronics field, not a power engineering one! The waveform below shows the capacitor switching transient captured inside a facility when the bank was switched on at the utility substation.

Ahead of the rectifiers and storage capacitor is the EMC filter whose primary purpose is to stop the muck generated by the switching circuit from being radiated onto the mains, and not as protection for the power supply. By doing so the manufacturer can make sure all the equipment used for semiconductor production has been tested and certified to SEMI F47 standard. Low-Frequency Decaying Ringwave This cbbema describes a decaying ringwave transient cutve typically results from the connection of power factor correction capacitors to an AC distribution system.

The frequency of this transient may range from Hz to 5 kHz, depending upon the resonant frequency of the AC distribution system.

Understanding the CBEMA curve – Technische Informationsbibliothek (TIB)

The second the amplitude and duration of the cbeja voltage. The interruption may last up to 20 milliseconds. These instruments, when located near the suspected disturbance, or when measuring the unusual operation of the power distribution system, will provide data on voltage variations and fluctuations and curv specifics on how the power quality problem places the equipment at risk.


The Information Technology Industry Council ITIC decided to create their own version of this curve shown in blue in the above graph as their belief was equipment was still prone to being damaged under the then present curve limits.

Limit the search to the library catalogue. The curve describes both steady state and transitory conditions. Browse subjects Browse through journals Browse through conferences.

Voltage Disturbance

The link in the article to the complete copy of the Application Note does not work. The best scientific interpretation of the curve can be given in terms of a voltage standard applied to the DC bus voltage of a rectifier load. The intent was to derive a curve that can better reflect the performance of typical single-phase, V, 60 Hz computers and their peripherals, and other information technology items like fax machines, copiers and point-of-sales terminals.

If ITE is subjected to such conditions, damage may result. Unless the curve was stipulated in the planning phase of a project or contract it will hold no ground apart from guidance as to a possible compatibility issue between the quality of the supply and the device running on that supply. Our next category down is Type II. Moreover, the instrumentation to check compliance with the curve appears to be easier to design because of the simplified way the acceptable region is represented.

It is felt that equipment fitted with a filter should be able to withstand greater deviations the shorter the timing of the deviation. There are cbems many variables – power loading, nominal operating voltage level, and process complexity, to try to apply xbema one-size-fits-all ITIC curve. The magnitude of transient is expressed as a percentage of the peak of 60Hz nominal voltage not the RMS value.

In other words, t he concept is that if the supply voltage stays within the acceptable power area then the sensitive equipment will operate well. The basis of this curve is supported by tests that were conducted on a representative sample of eight PC power supplies supplied by eight different manufacturers. This range is those deviations with extremely sharp rise and fall times deviate from and then return to the normal waveform extremely quickly.

Press and information Press releases Press Archives. The transient is assumed to be completely decayed by the end of half-cycle in which it occurs.


File:CBEMA – Wikimedia Commons

Power Quality in Electrical Systems. Other voltages are not specifically part of this and it is the responsibility of the user to verify that the curve is applied correctly at other voltages. High-Frequency Impulse and Ringwave: If our hypothetical Mr. After some minor modifications to the proposal, the ESC-3 working group approved this initial version of the curve, which remained unchanged until early in However, developing a single power acceptability curve to capture all these possible scenarios is nearly impractical.


Views View Edit History. Changes occurring faster than this e. Most modern ITE equipment are powered by a switched mode power supply. By doing this it would appear as if these guys sure know how to make things complicated! It is not intended to serve as a design specification for products or AC distribution systems.

This curve provides an AC voltage boundary that most information technology equipment ITE can tolerate or ride through without experiencing unexpected shutdowns or malfunctions. Voltage dropout includes both severe RMS voltage sags and complete interruptions of the applied voltage, followed by immediate re-application of the nominal voltage. Furthermore, balanced voltage sag events in three phase systems can be treated effectively as a single phase equivalent.

But there are two more required to fully indicate the extent of the disturbance, and they are the speed at which the voltage fell at the start of the short, and the speed of recovery when the short let go.

Also, the CBEMA curve illustrates that voltage levels below nominal are acceptable, provided that they do not drop below the magnitude and duration indicated by the curve.

British Library Conference Proceedings In the center of the plot is the so called acceptable area. Also, it is used as a reference to define the withstand capability of various loads and devices for protection from power quality problems. As can be seen this is mainly a flat line as anything out of this range can affect equipment function through under-voltage causing it not to run and overvoltage causing failures.