TechTopics No. 92      

Heat generation estimation for SIMOVAC non-arc-resistant and SIMOVAC-AR arc-resistant medium-voltage controllers

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

 

Component size
Fuse size
Typical full-load amperes (FLA)1
Full-voltage, non-reversing (FVNR); full-voltage reversing (FVR)
Contactor 400 A
2R
27 A
43 W
Contactor 400 A
3R
40 A
57 W
Contactor 400 A
4R
60 A
88 W
Contactor 400 A
6R
83 A
118 W
Contactor 400 A
9R
121 A
181 W
Contactor 400 A
12R
151 A
228 W
Contactor 400 A
18R
241 A
451 W
Contactor 400 A
24R
343 A
692 W
Contactor 400 A
15E
11 A
22 W
Contactor 400 A
20E
14 A
24 W
Contactor 400 A
25E
18 A
27 W
Contactor 400 A
30E
21 A
30 W
Contactor 400 A
40E
28 A
43 W
Contactor 400 A
50E
35 A
46 W
Contactor 400 A
65E
46 A
59 W
Contactor 400 A
80E
56 A
70 W
Contactor 400 A
100E
72 A
87 W
Contactor 400 A
125E
88 A
104 W
Contactor 400 A
150E
105 A
120 W
Contactor 400 A
175E
130 A
167 W
Contactor 400 A
200E
140 A
186 W
Contactor 400 A
250E
180 A
254 W
Contactor 400 A
300E
225 A
354 W
Contactor 400 A
350E
263 A
448 W
Contactor 400 A
400E
300 A
562 W
Contactor 400 A
450E
348 A
659 W

Approximate heat generation (in watts) for SIMOVAC non-arc-resistant and SIMOVAC-AR arc-resistant medium-voltage controllers

Component size
Fuse size
Typical FLA1
FVNR; FVR
Contactor 720 A
38R
490 A
758 W
Contactor 720 A
48X
600 A
956 W
Contactor 720 A
57X
689 A
1,247 W
Contactor 720 A
450E
348 A
503 W
Contactor 720 A
600E
451 A
724 W
Contactor 720 A
750E
520 A
956 W
LIS switch 600 A
450E
348 A
439 W
LIS switch 600 A
600E
451 A
586 W
LIS switch 1,200 A
750E
520 A
650 W
LIS switch 1,200 A
900E
630 A
1,015 W
Vertical section with main bus
----
1,200 A
188 W
Vertical section with main bus
----
2,000 A
206 W
Vertical section with main bus
----
3,000 A
250 W
Vertical section with main bus
----
4,000 A
413 W
Space heaters per vertical section
----
----
200 W
Voltage transformers (VTs) (set of three, including isolation switch)
----
----
50 W

Conversion factor: Watts x 3.415179 = BTU/hour.

 

Footnote:

  1. 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.

Component
Quantity
Watts/component
Total
Vertical section with 3,000 A main bus, with total loading 2,200 A
6
220 x (2,200/3,000)2 = 108 W
648 W
Controllers 400 A with 12R fuses
3
228 W
684 W
Controller 400 A with 24R fuses
1
692 W
692 W
Controllers 400 A with 250E fuses
2
254 W
508 W
Controller 720 A with 57X fuses
1
1,247 W
1,247 W
600 A LIS with 450E fuses
1
439 W
439 W
Space heaters
6
200 W
1,200 W
VTs, one set of three
1
50 W
50 W
Total heat generation for assembly
 
 
5,468 W

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