**4. Heat and Power Loss**

The IXXH110N65C4 IGBT has a high-power density capable of 235 to 110 A of continuous current at 25 and 110 ◦C, respectively. The short circuit safe operating areas are listed at 600 A for 1 ms and 220 A for 10 μs at 25 and 150 ◦C, respectively. The switch was heat-tested in open air using a R2A-CT4–38E heatsink to determine the maximum continuous current rating of the SSCB. The experiment was conducted using a DC power source supplying 50.9 V DC to the NHR 4760 DC load bank. The current level was varied from 0 to 10 A, and each level was maintained for a period of no less than 4 min. The maximum surface temperature of the heatsink was recorded via an infrared thermometer using an emissivity of 0.94, and the forward voltage drop was recorded at every step. The power loss of the switch was then calculated, and the results are shown in Table 1.


**Table 1.** Experimental results of heat and power loss.

The following equations, derived from Figure 7, were used to predict the on-time losses and temperature rise of the SSCB during a steady state operation:

$$P\_{\rm d} = 1.0347 \ast \text{I}\_{\rm c} - 0.4667, \text{ where } \text{I}\_{\rm c} \ge 1 \text{ A}, \tag{7}$$

$$\mathbf{T\_{sw}} = \mathbf{5.2358} \ast \mathbf{I\_c} + \mathbf{22.013}, \text{ where } \mathbf{I\_c} \ge \mathbf{1 A\_\prime} \tag{8}$$

where Ic is the continuous current of the SSCB, Pd is the power dissipated in the switch, and Tsw is the temperature of the switch. The slope of Tsw indicates that the temperature will increase 5.24 ◦C above the ambient per amp of continuous current. Combining Equations (7) and (8) reveals a temperature increase of 5.06 ◦C per watt consumed. The temperature analysis indicates that, under the current open-air conditions, the IGBT's optimum safe current rating is between 8 and 15 A and a 41.92 ◦C to 78.6 ◦C rise above the ambient temperature is to be expected. However, alternate cooling techniques that could be used to improve the thermal performance are discussed in [21] and should be considered when additional current is needed or ambient temperatures are unpredictable.

**Figure 7.** Power dissipated in the switch (**above**) and heat generated (**below**).
