In the case of an incident-energy calculation, the current is the arcing short-circuit current. IEEE Amendment A includes an 85 percent multiplier that can be used to reduce the arcing current as a what-if scenario in case the actual arcing current is lower than the calculated value. If this occurs, the lower current and longer arcing time could result in a greater total incident energy, and that value would be used instead.
IEEE provides three equations for determining the incident energy at a specific working distance. The first two equations are used to calculate the incident energy normalized to a inch mm working distance and an arcing time of 0. The third equation is used to adjust the normalized value to the actual working distance and arcing time for specific conditions. Logarithm functions are common on most scientific calculators and are often shown as a LOG button.
Use —0. Equation 3— Adjustment from normalized conditions to a specific working distance and arcing time:. Note: IEEE includes a constant of 4. No C f is used above 1 kV. As an example, Figure 1 illustrates a one-line diagram with a volt V panel PP An available arcing short-circuit current of 16, amperes A was previously calculated in part 2 of this series.
The arcing time is given as 0. A mm gap distance and 1. An inch mm working distance was selected from Table 2. The transformer connection shown on the one-line drawing indicates the system is grounded. To aid in the calculation process, two worksheets were developed.
Worksheet A Figure 2 is used for calculating the normalized incident energy, and worksheet B Figure 3 is used to calculated the incident energy adjusted for the specific working distance and arcing time.
Step 1: Using the arcing current I a of Step 2: Select the gap distance of 25 mm from Table 1 since the equipment is a V panelboard. Multiply it by 0. Step 3: Since a panel behaves like a box, select the value of K 1 as Step 4: The transformer symbol on the one-line diagram indicates the V system is grounded. Therefore, select the K 2 value based on whether the power system is effectively grounded.
Step 5: Add the values from steps 1 through 4 to determine the logarithm of the normalized incident energy E in. Step 6: Raise the number 10 to the value found in step 5. This is the incident energy normalized to a working distance of 24 inches and a duration of 0. Incident-energy worksheet B is used to convert the normalized value to an incident energy at a specific working distance and arcing time used in the study.
Step 1: This step is used to adjust the incident energy from the normalized inch mm working distance to the actual working distance D used for the equipment under study. Step 2: Incident energy is directly proportional to the arc duration. This step scales the incident energy by the ratio of the actual arcing time in seconds to the 0. The arcing time was given as 0. The resulting incident energy is 2. The arc rating of the protective clothing and equipment that should be used at this location when an arc flash hazard exists can be selected to have a rating sufficient for this value.
Demand - Flow of air at specific conditions required at a point or by the overall facility. McGuire Air Compressors, Inc.
Advantage Compressors. Duplex Advantage HP. Replacement Pumps. Oil-Less Medical Air Compressors. Compressed Air System Maintenance. Troubleshooting your compressed air system. Compressed Air Glossary. Service Record Charts. Refrigerated Dryers Basics. Are you Wasting Valuable Compressed Air? Compressed Air Safety Information. Electrical Specifications for Champion Compressors. The most used, most needed and most valuable Compressed Air Formulas. What's your Compressor's Electrical Energy Cost?
Barometric pressure must be considered to obtain true or absolute pressure Load Time - Time period from when a compressor loads until it unloads. Need a quote? Call Search Search.
0コメント