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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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. The standard has been implemented by essentially all semiconductor fabs and has been a huge cost saver for the industry. People tend to extrapolate these curves to V or even higher voltages and also as a general metric of incoming power quality.

While there is no harm in using this as a reference to establish a baseline power quality, it is important to recognize that the original intent of the curve was for V single phase computer equipment. Information technology equipment could include single phase computers, printers, scanners etc.

However, if such an event persist for a longer time, then the sensitive equipment might fail. In using the CBEMA curve, one must first determine the xbema of the power quality disturbances that are most prevalent in a facility.

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. The IEC terminology for this phenomenon is voltage dip. The normal functional state of the ITE is not typically expected during these conditions, but no damage to the ITE should result. 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.


Services for libraries National interlibrary loan International interlibrary loan. This is followed cvema a low voltage occurring on the said phases, and this then followed by another set of transients as well cbemq the cudve return to normal operating voltage.

ITIC Curve – Voltage Disturbance

Tables of content are generated automatically and are based on records of articles contained that are available in the TIB-Portal index. This transient may occur when large loads are removed from the system or when voltage is supplied from sources other than the electric utility. Obviously, this is quite an extension from the initial intent of describing the power quality performance of typical mainframe computers.

The moment it is modified it is no longer that curve. Advanced Search Watchlist Search history Search help. These instruments, when located near the suspected disturbance, or cruve 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.

So we have presented two needs for a tolerance curve, both as the means to test a supply with the cuve being before and after installation. Their timing falls anywhere between extended lightning strikes through to switching glitches transformer tap changes etc. 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.


These two limits, therefore, represent the wide input voltage range most SMPSs now comfortably operate on. Voltage dropout includes both severe RMS voltage sags and complete interruptions of the applied voltage, followed by immediate re-application of the nominal voltage.

The author briefly discusses power system problems and their analysis. Very short disturbances tend to leave the running voltage unchanged.

Discussion A brief description of the individual conditions that are considered in the ITIC curve is provided in this section. SEMI F47 suggests that semiconductor manufacturers may use this standard in their specification whenever they purchase equipment. It should be noted that the individual manufacturers performance to input voltage fluctuation is difficult to quantify as each many use a different technology inside their switched mode power supply.


File:CBEMA Curve.png

Does anyone know what happened on the ITI Technical page went? The CBEMA curve is only one of many ‘tolerance curves’ within industry it specifically designed as a measure of compatibility for IT equipment. Changes occurring faster than this e. As an example, take a temporary short occurring between two phases on the output of a 3-phase transformer. Reading desks and facilities Computer workstations Printing — photocopying — scanning Wireless LAN Interactive whiteboards Study cubicles Workstation for the blind and curce impaired.

This page was last edited on 10 Marchat This transient could occur during a temporary fault in the power system followed by clearing of the fault.