24v dc motor control

Discussion in 'The Projects Forum' started by Jaffacakes, Oct 9, 2016.

  1. Jaffacakes

    Thread Starter New Member

    Oct 9, 2016
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    Hi

    Can anyone help im building a mini machine that requires a 24v dc motor. Im controller this motor with pwm from a raspberrypi connected to an arduino 43amp h bridge. The motor im using is a 24v 200watt electric scooter motor.

    When i run my program motor turns fine and adjusts up and down as i want but the motor casing gets extremely hot and starts smelling, also heat sink on driver is very hot too.

    Am i doing something wrong i only have a little knowledge.

    Much help appreciated.

    Andy
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Welcome to AAC!
    If 200W is the electrical input rating and the motor is, say, 80% efficient, then 40W of heat is being dissipated. Not surprisingly the motor will get hot. For its intended use on a scooter there would be airflow to cool it. Heatsinks are expected to get hot, but forced air cooling of the heatsink might be needed if you can't keep your finger on it for 5 secs.
     
  3. Jaffacakes

    Thread Starter New Member

    Oct 9, 2016
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    Hey thanks.

    The motor is 24v 200watt output and says its rated at 10.9 amps.

    The motor itself is extremely hot, so would you recommend putting a fan on both or should i use a different motor etc?.

    Andy
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    So, in theory 62W of heat to dissipate! Do you have an alternative motor in mind?
     
  5. Jaffacakes

    Thread Starter New Member

    Oct 9, 2016
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    Is there a reason why i cant use this motor?.
    I wanted to use it to drive a few belts so needed something with a bit of power unless you can advise of something else.
    Or could i just put a cooling fan on both of them?.
     
  6. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    I'd give the fans a try.
     
  7. Jaffacakes

    Thread Starter New Member

    Oct 9, 2016
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    Hi thank you, I'll give that a go!, just cant understand why motor is so hot when i run it. When i run it slow its getting approx 6v this is without any load yet?.

    Andy
     
  8. ian field

    Distinguished Member

    Oct 27, 2012
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    The TS said it started smelling - so I wondered if the PWM frequency was high enough to cause eddies in the rotor/stator laminations.

    High PWM frequency would also mean the transistors were in transition (linear region) for a greater percentage of the cycle time.
     
  9. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    That's a possibility.
     
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Is it a P.M. motor or wound field? Series or shunt field?
    Max.
     
  11. Jaffacakes

    Thread Starter New Member

    Oct 9, 2016
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    Hi

    Sorry im a little new . Its an electric scooter motor believe its brushed.
     
  12. Jaffacakes

    Thread Starter New Member

    Oct 9, 2016
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  13. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Yeah, but it can be any of the above.
    Max.
     
  14. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If you short the two motor wires together and try and spin the motor, if you meet with resistance to turning then it is a P.M. motor.
    Max.
     
  15. Jaffacakes

    Thread Starter New Member

    Oct 9, 2016
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    Thank you.

    Can i ask whats the difference between the 3 and how it affects everything?.
     
  16. ian field

    Distinguished Member

    Oct 27, 2012
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    Direction on a PM motor depends on supply polarity.

    A field coil motor can run on AC and always spins the same direction regardless of polarity.
     
  17. Jaffacakes

    Thread Starter New Member

    Oct 9, 2016
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    Ok thanks , this motor drives in different directions depending which way supply is connected.
     
  18. Jaffacakes

    Thread Starter New Member

    Oct 9, 2016
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    Hi All

    Thank you for your input on this. Ive just changed my frequency setting in the raspberrypi from 50 to 800 runs alot smoother. Could anyone point me in the correct setting, as this motor will need to run at low speed and high speed.

    Everything is running much cooler now just by changing this setting.

    Andy
     
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