AN4043 datasheet(49/60 Pages) STMICROELECTRONICS

49 / 60 page

AN4043

Power losses and dissipation

Doc ID 022726 Rev 2

49/60

4.4

Power loss calculation example

As a result of power loss calculation and thermal aspects, fully treated in the previous

sections, it is possible to simulate the maximum IC(RMS) current versus switching frequency

curves for a VVVF inverter using a 3-phase sinusoidal PWM and a six-step 120° switching

modulation to synthesize sinusoidal output currents.

The curves graphed in

Figure 33 represent the maximum current managed by the SLLIMM-

nano in safety conditions, when the junction temperature rises to the maximum junction

temperature of 150 °C for three ambient temperatures (25, 50 and 75 °C), which is a typical

operating condition to guarantee the reliability of the system. These curves, functions of the

motor drive typology and control scheme, are simulated under the following conditions:

●

VPN = 300 V, ma = 0.8, cos = 0.6, Tj = 150 °C, Tc = 100 °C, fSINE = 60 Hz, max. value of

Rth(j-c), typical VCE(sat) and Etot values.

Table 11.

Cauer and Foster RC thermal network elements

Element

Zth(j-a) Cauer Network

Zth(j-a) Foster Network

R1 (°C/W)

8.96E-01

1.81E-01

R2 (°C/W)

9.37E-01

1.71E-01

R3 (°C/W)

5.92E-01

8.12E-02

R4 (°C/W)

1.37E-02

5.11E-02

R5 (°C/W)

2.11E-02

1.86E-01

R6 (°C/W)

2.84E+00

6.58E-01

R7 (°C/W)

1.26E-01

5.00E-04

R8 (°C/W)

4.48E-02

6.95E-02

R9 (°C/W)

4.06E-01

5.14E-01

R10 (°C/W)

4.93E+00

4.43E+00

R11 (°C/W)

9.38E+00

7.90E+00

R12 (°C/W)

2.99E+01

3.58E+01

C1 (W·sec/°C)

6.25E-04

1.55E-01

C2 (W·sec/°C)

3.81E-03

1.67E-01

C3 (W·sec/°C)

4.69E-03

1.19E+00

C4 (W·sec/°C)

2.41E-03

9.09E-01

C5 (W·sec/°C)

4.39E-03

1.84E-02

C6 (W·sec/°C)

3.27E-03

1.07E-03

C7 (W·sec/°C)

1.82E-02

1.77E-03

C8 (W·sec/°C)

1.32E-02

8.80E-02

C9 (W·sec/°C)

3.63E-03

1.19E-02

C10 (W·sec/°C)

6.72E-02

4.74E-02

C11 (W·sec/°C)

2.75E-02

2.35E-01

C12 (W·sec/°C)

2.22E+00

1.75E+00

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