UL 1414 Section 16: Impulse Voltage Test

16.1 Twelve samples of a capacitor are to be tested as described in 16.2 and 16.3. As a result of the tests, there shall not be permanent breakdown or flashover.

16.2 Each capacitor is to be mounted by the leads in a fixed position with the capacitors randomly oriented in any end-use configuration not prohibited by the physical construction of the capacitor. The free length of the leads is to be at least 1 in (25.4 mm) unless the samples are provided with shorter leads.

16.3 Each individual capacitor is to be subjected to a maximum of 24 impulses of the same polarity. The time between impulses shall not be less than 10 s.

16.4 The peak value of the impulse voltage (Vp) is to be 4 kVdc for Class X1 capacitors.
16.5 The peak value of the impulse voltage (Vp) is to be 8 kVdc for Class Y1 capacitors.
16.6 The peak value of the impulse voltage (Vp) is to be 5 kVdc for Class Y2 capacitors.

16.7 When any three successive impulses are shown by the oscilloscope to have a waveform indicating that no self-healing breakdowns or flashovers have taken place in the capacitor, no further impulses are to be applied, and the capacitor complies with the requirement. When all 24 impulses have been applied to the capacitor, and three or more of the waveforms indicate that no self-healing or flashovers have occurred, the capacitor complies with the requirement. When less than three waveforms are of the required waveform, the capacitor does not comply with the requirement.

Exception: When the waveform has a dampened oscillation, the peak-to-peak voltage (VPP) of the oscillation shall not be greater than 10 percent of the peak voltage (VP) of the impulse.

16.8 The waveform is to be determined by the circuit components in the test circuit. Figure 16.2 illustrates the circuit to be used in performing this test. The parameters of the components in the test circuit are to be in accordance with Table 16.1.