• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 30 subscribers
  • Views 277 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

AFE3010: AFE3010: Total Reaction Time Estimate

AFE3010: Trip Time

John Hodges
Prodigy 20 points
Part Number: AFE3010

Tool/software:

Hello

I have a question about the AFE3010

My requirement is" GFI (Ground Fault Interruption) is performed by sensing the current flowing through both the live/hot and neutral lines. The current going out on the line must be equal to the returning current. If there is a difference, greater than 10mA, a fault is triggered and in less than 30mS the outlet will trip, meaning an electromechanical relay is opened and power is no longer present at the contacts."

I am well aware that UL943 only requires < 1 second.  UL943 is not my requirement.  Is there anyway to "speed" up the trip time with this device?

Thank you in advance

  • 0
    TI__Mastermind 32395 points

    Hello Appreciated Engineer,

    I am looking this question over and will respond promptly.

    Sincerely,

    Peter

  • 0
    TI__Mastermind 32395 points

    Hey John,

    The AFE3010 responds to ground fault current much faster than the strict UL 943 Requirement as listed in the Electrical Characteristics Table.

    If you want the AFE3010 to react in < 30 ms, then you need to provide a signal current at FB pin that causes voltage at OUT (Vout) to be > 4.8V or < 0.2V. These are internal comparator threshold levels that cause device to activate SCR pin with fastest reaction time (~10 ms typical, 12ms max). You can assume each comparator level can have +/-3.5% error.

    Unfortunately, you cannot turn off smaller fault current comparators. If you scale the gain so 10mA fault makes Vout >4.8V, then you are also making a ~1mA fault current trip the slowest comparators of 150ms (Vout>2.75 or Vout < 2.25V). This may be undesirable if you are wanting to reject all fault currents < 10mA.

    I mention a "signal current" because the internal amplifier of AFE3010 is a current-feedback amplifier, not a voltage feedback. This is why it is used to sense coil current from the current transformer. Datasheet's typical schematic has  the feedback, gain setting resistor (R7) as 36kΩ. If you want to make 10mA fault current create fastest trip time, then R7 would need change to ~180kΩ.

    Please respond with any other questions you have.

    Best,

    Peter