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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This template also does not apply to postage stamp designs published by the United States Postal Service since Low-Frequency Decaying Ringwave This region describes a decaying ringwave transient which typically results from the connection of power factor correction capacitors to an AC distribution system.

However, there is one thing that timing does not take into account and that is the energy released during such an event, energy usually being measured in Joules. This could include thyristor controlled heaters, some digital clocks etc. Power Systems Engineering Research Center. Show all volumes and issues. Any voltages in this range may be present for an indefinite period and are a function of the normal loadings and losses in the distribution system.

File:CBEMA – Wikimedia Commons

Low pass filters attenuate frequencies above their cut-off. Voltage sags occur when then there is some fault on the system or during starting of large loads motors etc. The magnitude of the transient is expressed as a percentage of the peak 60 Hz nominal voltage not the RMS value. Computers, programmable logic controllers, distributed processing units, instrumentation, and other sensitive solid-state systems are voltage and time sensitive.


The basis of this curve is supported by tests that were conducted on a representative sample of cudve PC power supplies supplied by eight different manufacturers. Many will try to use one point to indicate a complicated disturbance.

Working right to left we’ll cover Type III category first. In the center of the plot is the so called acceptable area. Limit the search to the library catalogue. For further questions please contact our TIB customer service. Voltage dips and swells as well as outages and transients will seriously affect their operation.

If the file has been modified from its original state, some details such as the timestamp may not fully reflect those of the original file. However, developing a single power acceptability curve to capture all these possible scenarios is nearly impractical.

One of the most effective ways to prepare for optimum operation of sensitive electronic equipment is to understand and use the Computer Business Equipment Manufacturers Association CBEMA curve and related guidelines.

The interruption may last up to 20 milliseconds.

Power Systems Engineering Research Center. The time period is from one half-cycle up to where Type III begins. The measurements and results can then be analyzed in combination with the CBEMA curve to help understand the nature of power quality disturbances.

File:CBEMA Curve.png

With electronics becoming more and more sensitive this could be believable especially as designers are shaving off far too much in the designs to make them more economical at the expense of robustness. The moment it is modified it is no longer that curve.

If our hypothetical Mr.


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. Does one need to be an ITIC member to access it? The higher the frequency, the higher the attenuation.

As their frequency component is so high, wiring alone tends to provide huge attenuation let alone the filters found in most modern power supplies or transformers. The waveform below shows the capacitor switching transient captured inside a facility when the bank was switched on at the utility substation.

Told you, Power Quality is an electronics field, not a power engineering one! 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 the specifics on how the power quality problem places the equipment at risk. Course reserves Setting up a course reserve Form for setting up a course reserve.

Tables of content are generated automatically and are based on records of articles contained that are available in the TIB-Portal index. The frequency of this transient may range from Hz to 5 kHz, depending upon the resonant frequency of the AC distribution system. However, one should be careful and should keep in mind that the ITIC curve is not intended to reflect the performance of ALL electronic-based equipment. For a complete copy of the Application Note Click here References: