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MicroHarmony Cell Sizes 40 - 260A Manual
9.5.4
Capacitor Losses vs Output Current
Capacitor losses are based on I^2 x R losses using ESR at 120Hz. This is a conservative approach to estimating
capacitor losses. Furthermore, a conservative ESR of 9 mohms is used for the 40-140A capacitors, and 17 mohms for
the 200-260A cells. In actual use, the effective ESR will be lower than this and losses will be slightly lower. Also, a
conservative RMS ripple current factor of 78% output current is used.
Pcaps = (Iout x 0.78 / Np)^2 x ESR x Ncaps
The table and charts below can be used for estimating capacitor losses as a function of cell output current.
Iout
40A
70A
100A
140A
25
10.3
5.1
3.4
2.6
50
41.1
20.5
13.7
10.3
75
92.4
46.2
30.8
23.1
100
82.1
54.8
41.1
125
85.6
64.2
150
123.2
92.4
175
125.8
200
164.3
225
250
275
300
325
The data above assumes 0.85 motor power factor, 0.95 motor efficiency, 600Hz switching frequency, 60Hz output
frequency, 9mohm ESR (17mohm ESR for 200/260A cell), and Icap=Iout x 0.78. For individual capacitor losses,
divide the total given by the number of capacitors within the cell.
Alternatively, capacitor bank losses can be estimated as follows:
40A cell:
Pcaps = 0.0164 x Iout ^2 + 0.002 x Iout - 2.13E-14
70A cell:
Pcaps = 0.0082 x Iout ^2 + 0.0018 x Iout - 0.075
100A cell:
Pcaps = 0.0055 x Iout ^2 + 0.002 x Iout - 0.07
140A cell:
Pcaps = 0.0041 x Iout ^2 - 0.0004 x Iout + 0.0429
200A cell:
Pcaps = 0.0103 x Iout ^2 - 0.0012 x Iout + 0.782
260A cell:
Pcaps = 0.0078 x Iout ^2 + 0.0007 x Iout - 0.0503
For individual capacitor losses, divide the above results by:
40A cell:
3
70A cell:
6
100A cell:
9
140A cell:
12
200A cell:
9
260A cell:
12
19001467: Version 1.0
200A
260A
6.5
4.8
900
25.9
19.4
58.2
43.6
800
103.4
77.6
700
161.6
121.2
600
232.7
174.5
500
316.7
237.6
400
413.7
310.3
523.6
392.7
300
646.4
484.8
200
782.2
586.6
100
698.1
0
819.3
s
Losses vs Output Current
40A
70A
100A
140A
0
50
100
150
Output Current, Arms
Application Notes
200A
260A
9
200
250
300
9-9
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