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Difference between Single Protection and Double Protection in UL1577

Takeshi Sasaki
Expert 4480 points

Hi team,

Could you tell me the difference between Single Protection and Double Protection in UL1577? I'm confused that is defined by physical insulation structure or is only defined by the isolation voltage.

Best regards,

  • 0
    TI__Genius 10855 points

    Double Protection isolators need to pass 2 additional tests when compared to Single Protection isolators.

    Single protection isolators are required to pass the following tests:

    1- Dielectric Voltage-Withstand Test

    2- Overload Test

    3- Limited Thermal Aging Test

    Double protection isolators need to pass the tests above and the following additional test:

    4- 20 kV Discharge Test

    5-  1008 Hours Isolator Life Test

    Additionally, UL restricts the use of Double Protection Isolators to equipment rated up to 250 Vrms whereas Single Protection Isolators can be used in equipment rated up to 600 Vrms or dc.

  • 0 in reply to Saleem Marwat
    TI__Expert 4480 points
    Hi Saleem,

    Thank you for your clear-cut answer. I understood, definitely.
  • 0 in reply to Saleem Marwat
    Prodigy 20 points
    Hi:
    I am confused with the relation between single protection and reinforced insulation.
    Is UL1577 related to reinforced insulation?
    Could single protection device be used as reinforced insulation according to IEC60601-1(250Vrms)?
  • 0 in reply to peng hu
    TI__Genius 10855 points
    UL 1577 Single Protection rating has nothing to do with Reinforced insulation according to IEC 60601-1. These are two totally different standards. UL 1577 is a isolator component standard and IEC 60601-1 is a Medical system standard.

    Most of TI's isolators are certified as UL 1577 Single Protection. Many of the same devices (such as ISO77xx and ISO78xx) have also been certified as VDE reinforced components. Additionally these devices are also certified for use in medical systems (IEC 60601-1) reinforced up to 250 Vrms (DW package) or 400 Vrms (DWW package).
  • 0 in reply to Saleem Marwat
    Prodigy 20 points
    Hi Saleem:

    Thank you for your reply!

    I have one more question:

    According to ISO78xx datasheet ,it can provide 2 MOPP in 250Vrms system, In general the test voltage frequency is 50 or 60Hz, so in a system with frequency of 30kHz to 100kHz (250Vrms ),can it provide 2MOPP ?

    Best regards