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.60AMP DC Motor

Discussion in 'Sensors and Actuators' started by DJoyce, Feb 8, 2010.

  1. DJoyce

    DJoyce

    3
    0
    Feb 8, 2010
    I have a .60 amp dc motor wired to a speed control board. What would be the best way to fuse this motor? Is it ok to fuse it between the controller and motor. If it is ok does it matter which wire the fuse goes to?
     
  2. Resqueline

    Resqueline

    2,848
    1
    Jul 31, 2009
    In general a fuse is put as close to the power source a possible. If you fuse at the motor it doesn't matter which wire.
    But with more detailed info we might be able to provide better answers.
     
  3. DJoyce

    DJoyce

    3
    0
    Feb 8, 2010
    .60 amp dc motor

    Thanks for your reply. This dc motor and speed control board is in one of our machines. What we think is ocassionally happening is the gear box leaks and drips oil on the electrical parts of the motor and causes it to blow along with the speed control board. I thought it would be a good idea to fuse the motor to save the control board from blowing also. Do you think it would be best to thermal protect the motor instead of using a fuse? If I go with the fuse I was thinking about using a 1.5 amp slo blo.
     
  4. Resqueline

    Resqueline

    2,848
    1
    Jul 31, 2009
    If it's a slowly building overload then an ordinary fuse might do the job. If it's a sudden short then ordinary fuses aren't fast enough to protect semiconductors, not even fast ones. 0.6A full load? What voltage?
    Oil shouldn't create shorts. What kind of motor is it? A geared coreless servomotor? I've known these to develop shorts due to wear. Silver powder gets packed in the commutator slots. This doesn't happen with carbon brushes on copper commutators though.
    How much is the speed controller rated at? Working protection depends on what's actually happening.
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,178
    2,690
    Jan 21, 2010
    I was thinking along the lines of using a large mosfet to limit the current (via suitable control circuitry) to (say) 3A and then fuse it as the original poster suggested.

    The limited current would still provide ample to blow the fuse, but *may* limit surges so that the controller is not damaged.

    Seems like a fairly complex solution though -- although, depending on the cost of the motors and controllers -- it may have a fairly short payback period.

    If the short is transient though, you may find that the fuse keeps blowing (regularly, not immediately) and the motor seems perfectly OK.
     
  6. DJoyce

    DJoyce

    3
    0
    Feb 8, 2010
    .60 amp dc motor

    Heres the specs on the motor. Parallel Shaft 90 VDC Gearmotor, Nameplate Speed 139 RPM, Input Power 1/20 HP, Gear Ratio 13:1, Overhung Load 90 Pounds, Full Load Torque 20 Inch Pounds, Full Load Current 0.60 Amp, Enclosure Totally Enclosed Nonventilated, Motor Type Permanent Magnet
    The motor is from Grainger part number 6Z916.
    Thanks
     
  7. Resqueline

    Resqueline

    2,848
    1
    Jul 31, 2009
    There are several discrepancies in their data.
    They state input power is 1/20hp which is 37.3W but 90V x 0.6A is 54W (= 1/14hp)
    Neither does it fit with the real output power: (20"lbf =) 2.26Nm x 2.32rps x 2 x pi = 32.9W (=1/23hp).
    Well it doesn't really matter. But is your speed control the one listed next to the motor? It's fused and can stand 124W or 1.38A.
    I see it uses carbon brushes so the silver dust theory is out. Other theories; cracks in brush holder with short to ground, or short to ground in windings. Would you be able to use an insulation tester on it?
    When it fails, is the motor hot? Is it at all possible the motor could be overloaded?
     
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