Duty cycle of DC motor

Discussion in 'General Electronics Chat' started by Dritech, Jul 17, 2013.

  1. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
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    5
    Hi,

    I am going to buy an actuator which make use of the motor below:

    http://www.gimsonrobotics.co.uk/HRS550-S_GR02-spare-motor_12V-18V.html

    To increase the duty cycle of this motor I was planning to attach a heatsink such as the one in the link below (including a cooling fan which will be bought separately):

    http://www.ebay.co.uk/itm/540-550-R...sGames_RadioControlled_JN&hash=item4cf4a4b0e6

    Will this method help increasing the duty cycle? also, the heatsink is for motors with a 35mm diameter. Can I remove that metal sheet from the motor so the heatsink will fit? and what is the purpose of that metal sheet?

    Thanks in advance.
     
    Last edited: Jul 17, 2013
  2. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
    1,758
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    What on Earth are you talking about?
     
  3. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    756
    5
    OK I know that my English is rubbish (it is not my mother language, sorry), but was it that hard for you to understand?

    I am going to buy an actuator with a 25% duty cycle. To attempt to increase the duty cycle I am going to mount a heatsink. Will that help increasing the duty cycle or not?

    Also, there is a metal sheet (or whatever it is called) around the motor. Can I remove it so the heatsink can fit better?
     
    Last edited: Jul 17, 2013
  4. wayneh

    Expert

    Sep 9, 2010
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    I believe the OP is asking if that heatsink will remove enough heat to allow increasing the duty cycle of the motor.

    Since the motor appears to rated for continuous duty anyway, the answer must be "NO", since you cannot get more than 100%.

    If you want to run at higher voltage AND high duty cycle, outside the ratings of the motor, I don't know how to predict results. Will the sink extend motor life? Probably. Will the motor's life be shortened compared to running below its rating? Probably.
     
  5. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
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  6. wayneh

    Expert

    Sep 9, 2010
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    Ah, much clearer now. But I don't feel any closer to the answer. Maybe the supplier knows WHY the rating is what it is, and whether heat removal might help. IMHO, you'll need larger vanes on that sink or more airflow to have a significant effect. I suppose you could estimate how much heat the motor is making and the heat sink supplier should be able to provide data on whether that sink can handle it and a given airflow rate.
     
  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    The duty cycle is generally related to how much heat builds up in the armature winding.

    That will be VERY load dependent as load determines the armature winding current and the winding heat is from I squared R losses.

    You really need to test. The motor should have a large range of load it can drive, so it's likely the motor will be capabale of 100% duty with a light load but is limited to 25% duty or less when moving high loads.

    A heatsink around the motor will help a bit, but the heat is is the armature winding not the stator magnets so the best cooling would be a fan forced system through the motor.
     
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