Conformity Magazine- May 2008 - (Page 38) Experimental Verification Extensive testing has been performed for radial type PTC devices, LVRXXX series, with both AC and DC voltages. Two models, LVR005 and LVR040, representing the smallest and largest current ratings in the series were used in this article for discussion. The ratings of these two models are shown in Table 1. A resistance versus temperature (R/ T) test as shown in Figure 1, and a power dissipation test for the device under tripped state, were performed before and after each conditioning test. These two tests characterize device performance before and after each conditioning test. A unique temperature derived from the R/T curve corresponding to measured trip resistance was used to quantitatively compare the device performance change after each test. Based on this study, we found that there is no significant difference in performance for the same voltage but different polarities. The AC test condition appears to be more severe than the DC test condition during the aging and overload/ endurance tests. Due to a maximum interrupt voltage rating of 265 Vac for Model LVR040, the four tests discussed in this article for Model LVR040 AC rating were performed at 265 Vac instead of 240 Vac. Aging Test Results The percentage change in the tripped temperature for the aging test is shown in Table 2. The average percent shift is consistently larger for the AC voltage test than for the DC test. The difference is about 6%, indicating that the higher voltage stress during the AC test played a major role in device performance. Note that samples used in the AC rating tests are different from those used for the DC rating tests presented in this article, even though they are labeled with the same sample number in the resulting tables. Model LVR005 Sample 1 2 3 4 5 6 Average 240 Vac 7.3% 7.8% 7.9% 6.9% 6.9% 8.4% 7.53% 240 Vdc 2.3% 0.8% 0.3% 1.4% 1.1% 3.8% 1.62% Model LVR040 265 Vac 12.9% 8.5% 13.0% 8.45% 11.6% 14.2% 11.44% 240 Vdc 4.6% 7.1% 7.0% 4.6% 4.4% 8.5% 6.03% Sample 1 2 3 4 5 6 Average Model LVR005 240 Vac 2.6% 2.2% 1.9% 1.9% 2.1% 2.7% 2.23% 240 Vdc 0.0% 0.8% 2.1% 2.5% 2.7% 2.0% 1.68% Model LVR040 265 Vac 0.1% 0.7% 3.6% 5.1% 0.1% 3.2% 2.13% 240 Vdc 0.8% 5.6% 11.4% 1.4% 3.6% 0.6% 3.90% Table 2: Percent shift of tripped temperature for samples after the aging test Model LVR005 Sample 1 2 3 4 5 6 Average 240 Vac 5.8% 7.5% 5.8% 5.5% 5.3% 7.0% 6.15% 240 Vdc 0.7% 0.5% 0.5% 0.8% 0.2% 1.1% 0.63% Model LVR040 265 Vac 1.3% 6.8% 3.2% 6.0% 2.8% 0.7% 3.47% 240 Vdc 1.0% 0.5% 0.7% 1.1% 0.2% 0.1% 0.60% Table 4: Percent shift of tripped temperature for samples after the cold operational test Model LVR005 Sample 1 2 3 4 5 6 Average 240 Vac 2.4% 2.2% 0.8% 1.2% 1.8% 1.4% 1.63% 240 Vdc 1.2% 2.8% 0.7% 0.4% 0.9% 1.2% 1.20% Model LVR040 265 Vac 0.2% 0.3% 0.1% 0.2% 0.3% 1.2% 0.38% 240 Vdc 5.4% 1.1% 0.5% 7.1% 0.1% 0.8% 2.50% Table 3: Percent shift of tripped temperature for samples after the overload/endurance test 38 Conformity mAy 2008 Table 5: Percent shift of tripped temperature for samples after the thermal runaway test
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.