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Electrically Isolated Semiconductor Devices
UL 1557

1.1 These requirements apply to semiconductor devices of the isolated-mounting type - thyristors, transistors, diodes, and the like, and hybrid modules consisting of combinations of these devices.

Note: 1.1 revised September 8, 2009

1.2 These requirements do not apply to snubber and commutation circuits associated with thyristors, transistors or other analog semiconductor devices.

1.3 These requirements cover the isolation performance of thyristors, transistors, diodes, and the like, and their combination in module packages and constructional features that are pertinent to that performance.

1.4 These requirements apply to isolated semiconductors for use as components in products. Compliance of an isolated semiconductor with these requirements does not determine that the semiconductor is acceptable for use as a component of an end product without further investigation. The acceptability of a semiconductor in any particular product depends upon its acceptability for continued use under the conditions that prevail in actual service.