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Thread: GE Multilin 369 Motor Protection Relay Power Source

  1. #1
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    GE Multilin 369 Motor Protection Relay Power Source

    I'm replacing two motor protection relays with new GE Multilin 369's. The current motor protection relays get their power from the same source as the motor, via a control power transformer that drops the voltage from 4160V to 120V. I'm just confused about a line in the GE Multilin 369 installation manual. It reads: "For applications where the control power for the 369 is available from the same AC source as that of the motor, it is recommended an uninterrupted power supply be used to power up the relay, or alternatively, use a separate DC source to power up." I guess I just don't understand the wording. Is this recommending to use a UPS for the multilin 369 power source. I was planning to use the control power transformer with the same power source of the motor.

  2. #2
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    I think they want to make sure the relay remains powered up even if the power source is off.
    Bob

  3. #3
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    You want the relay to still operate on a loss of power to the motor. Likely trip the breaker on UV

  4. #4
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    They are not talking about a UPS.

    From the manual:

    The Test Output Relay feature provides a method of performing checks on all relay contact outputs. The feature can also
    be used for control purposes while the motor is running. The forced state overrides the normal operation of the relay output.


    The forced state, if enabled (energized or de-energized), forces the selected relay into the programmed state for as long as
    the programmed duration. After the programmed duration expires, the forced state will return to disabled and relay operation
    will return to normal. If the duration is programmed as Static, the forced state will remain in effect until changed or disabled.
    If control power to the 369 is interrupted, any forced relay condition will be removed.
    The more they overthink the plumbing, the easier it is to stop up the drain

  5. #5
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    Quote Originally Posted by zog View Post
    Likely trip the breaker on UV
    I'm still a bit new to all this. What is UV?

  6. #6
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    Quote Originally Posted by jucesanc View Post
    I'm still a bit new to all this. What is UV?
    undervoltage
    Bob

  7. #7
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    we tap power off before the vcb
    you need the relay to remain energized if the vcb trips

  8. #8
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    Quote Originally Posted by zog View Post
    You want the relay to still operate on a loss of power to the motor. Likely trip the breaker on UV
    the uv coil is normally energized
    if you remove power it drops out

    the shunt coil needs power to trip, usually from a capacitive discharge ckt
    a C dumping to an L, very fast and positive

  9. #9
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    Quote Originally Posted by Ingenieur View Post
    we tap power off before the vcb
    you need the relay to remain energized if the vcb trips
    If the power to the motor is lost, why would we still need relay to be energized? What would the relay be protecting at that point?

  10. #10
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    Quote Originally Posted by jucesanc View Post
    If the power to the motor is lost, why would we still need relay to be energized? What would the relay be protecting at that point?
    so you can reset faults that latch
    possibly time and restart
    see trip messages/diagnostics

    suppose you cycle power to the relay and it attempts to restart?

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