difference：
UL1577 Requirements for Single Weight Protection Isolators:
The Single Protection Isolator is required to pass the following tests for certification:
- dielectric withstand voltage test.Isolation Voltage Test
- Overload test
- Limited thermal aging test
UL1577 Requirements for Dual Protection Isolators:
Compared to the single protection isolator, the double protection isolator needs to pass two additional tests, i.e. it needs to pass the above yes test and the following additional tests:
- 4- 20 kV discharge test
- 5-1008 hours isolator life test
- In addition, UL1577 limits the use of dual protection isolators to equipment rated up to 250 Vrms, while single protection isolators can be used in equipment rated up to 600 Vrms or dc.