Siemens is often asked to provide estimated heat generation data for our equipment. This issue of TechTopics provides information that allows calculation of approximate heat generated by the SIMOVAC non-arc-resistant and SIMOVAC-AR arc-resistant medium-voltage controller equipment under assumed loading conditions.
The heat generation data given in the table for motor controllers is on the basis of operation at 1.0 service factor, and assumes that each controller includes a 0.75 kVA control power transformer that is only lightly loaded when the motor is running. The current value for motor controllers is the current typical for a machine using the fuse size shown.
For transformer feeders with class E fuses installed in series with a class E controller, it is assumed that the continuous current in amperes is in the range of 70 percent to 80 percent of the E-rating of the fuse. For load-interrupter switches (LIS) with fuses, fuse current is also assumed to be in the range of 70 percent to 80 percent of the fuse E-rating. As with motor controllers, the current used is considered representative of the current for a transformer protected by the fuse size shown.
For applications which differ from these assumptions, convert the heat generation shown for the typical currents to that for the specific application by the ratio of the squares of the currents.
For the main bus, the data assumes operation at full-rated continuous current.
To estimate the heat generated under actual loading conditions, determine the component heat generation for each of the components indicated in the table, with adjustments if necessary for differing currents. For simplicity, assume that main bus loading in each vertical section is equal to the total estimated load of the controller lineup, and adjust the heat generated for each vertical section by the square of the percentage of total estimated load to rated main bus current. Space heater load should be assumed to be continuous.
Approximate heat generation (in watts) for SIMOVAC non-arc-resistant and SIMOVAC-AR arc-resistant medium-voltage controllers
Approximate heat generation (in watts) for SIMOVAC non-arc-resistant and SIMOVAC-AR arc-resistant medium-voltage controllers
Conversion factor: Watts x 3.415179 = BTU/hour.
Footnote:
- See text for assumptions used for typical current. For motors, typical current is that for a machine typically protected by the size of fuse shown. For transformers, current is in the range of 70 percent to 80 percent of the fuse E-rating, with specific value considered typical for a transformer protected by the fuse size shown.
As an example of the method of calculation, consider a lineup of controllers with six vertical sections, with the components shown in this table.
Should you have any questions about this issue of TechTopics or any of our products, solutions, or services, please contact your local Siemens sales representative for more information.
