Vacuum cleaner requirements

AN2777

8/13

Doc ID 14748 Rev 1

3

Vacuum cleaner requirements

3.1

Steady state thermal design

As for all power semiconductor applications, one main point to check is the thermal design.

It has to be checked to ensure the working junction temperature is below the maximum

References 3.)

Equation 2

In vacuum cleaners an efficient way to decrease the heatsink size is to put it in the air flow.

However, it is quite difficult to evaluate the required heat-sink size. A good way to check the

thermal design is then to measure the case temperature and check if this value is lower than

the specified value (see Figure 8, from T1235H-6 datasheet). This figure shows that for a

10 A rms current, the case temperature can reach 116 °C.

Experimental tests have been performed on a 2000 W vacuum cleaner. The maximum

dissipated power occurs for the maximum speed (delay between line zero voltage and

TRIAC turn-on is 0.75 ms, refer to Table 1 and Figure 12). The rms load current equals 10 A.

With a 20 cm² white aluminum plate (2 mm width), the case temperature reaches only

100 °C. This means that there is almost a 16 °C safety margin.

Figure 8.

Maximum allowed current versus case temperature for T1235H-6

RthHS ≤

Tjmax -Tamax

P

0

2

4

6

8

10

12

14

0

25

50

75

100

125

150

T

TO-220AB/D²PAK

-

TO 220AB

Insulated