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Lets talk about fan/blower motors (high vs low)

Discussion in 'Sensors and Actuators' started by spdjnky_42, Aug 23, 2017.

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  1. spdjnky_42

    spdjnky_42

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    Aug 23, 2017
    My DOWNDRAFT stove burnt the circuit board on the "high" side relay, for the downdraft blower. I switched the wires around to make sure it was in fact the relay. It was, the fan works on the high setting if I hook the high to the other relay. The non working side... relay still clicks and the board is burnt under it. Relay is fine, or appears to be, board is not deformed other then the copper path. Does a fan motor need both power sources for "high" vs "low" setting? Or, if I just simply switch the wires will I have my high setting back and just be out the low setting? I do not understand motor windings vs voltage vs high/ medium/ low settings???

    Also, Im not really understanding what burnt the board. Just a bad spot in the board? Or would it be the fact that when you turn the downdraft on its first setting (same button) is high instead of low. It was my understanding that a motor WITH a squirrel cage always started in low first to get it moving before the load of "high" was applied. Opposite of your typical fan motor. Guess I am wondering if the load of the grease, from the fact its a downdraft, created a large load and burnt the board. Having it start in low first would help this, would it not?
     
  2. duke37

    duke37

    5,362
    768
    Jan 9, 2011
    Unless more information is given, it is difficult to diagnose the problem.
    What is a DOWNDRAFT stove?
    Have you got pictures of the damage?

    If the copper traces on the board have failed, possibly due to a bad solder connection, I would replace them with a wire thick enough to take the motor current.
    Check the motor bearings to ensure that they are free. Starting the motor slow would lengthen the time that the motor is running on high current.

    Most small motors, squirrel cage, shaded pole or universal are switched directly on line. The current is limited by the motor and supply resistance, including the traces on the board.
     
  3. duke37

    duke37

    5,362
    768
    Jan 9, 2011
    Mods, please delete this thread, it is a duplication of another. My replay is still valid but is only a repeat of others.
     
  4. spdjnky_42

    spdjnky_42

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    Aug 23, 2017
    My apologies, I originally wanted this topic to be about how a fan can be variable speed. Hard to have the conversation without giving most the info on the other thread.
     
  5. Minder

    Minder

    2,955
    624
    Apr 24, 2015
    Most AC fans are either PSC (permanent start cap) or shaded pole motors, and are both induction motors.
    The former usually uses separate winding's for speed control, the latter, Triac (dimmer) control.
    M.
     
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