AN2991 Datasheet, PDF (4/14 Pages) STMicroelectronics – Single-phase induction motor drive for refrigerator compressor application

Single-phase induction motor drive topologies
AN2991
1.2.2
Current rating
Refrigerator or freezer compressors mostly feature input power in the range of 100-300 W.
The steady state current is then in the range of 0.5 to 3 A rms for a 220-240 V mains
voltage.
The highest current appears at start-up and can reach up to 4 times the steady state
current. Thermal calculations can demonstrate that, as these events last a short time, 6 A
devices can be used without any heat sink. For example, Figure 4 gives the junction
temperature increase of an ACST610-8T without any heat sink, due to the inrush current
which is measured through the start winding of a 150 W compressor. It shows that T_j only
reaches 77 °C, when coming from a 60 °C ambient temperature, and remains below the
maximum allowed temperature (125 °C).
Figure 4. Inrush current in start winding (150 W compressor)
Current in the device (A)
10
8
6
4
2
0
-2
-4
-6
-8
Time (s)
-10
-0.1
0.1
0.3
0.5
0.7
0.9
Junction temperature (°C)
80
Time (s)
78
76
74
72
70
68
66
64
62
60
-0.1
0.1
0.3
0.5
0.7
0.9
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Doc ID 15772 Rev 2