Time Delay Fuse for DC Motor

Discussion in 'General Electronics Chat' started by bassplayer142, Sep 22, 2010.

  1. bassplayer142

    bassplayer142 Thread Starter Active Member

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    Does anyone have any information about time delay fuses in series with a DC motor for protection against over current. If a DC motor is rated at 32 Amp stall current, what value of a fuse should I have? 30 Amps? An H-bridge I'm looking into is rated at 20Amps continuous with 30Amp peak.

    Any help is greatly appreciated. Thanks in advance!
  2. sgardner025

    sgardner025 Member

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    You may want to look at a bridge that will handle more current, or use individual mosfets and use a h-bridge driver ic. Another thing you may want to look into is using current sensing and the associated control methods instead of time delay fuses. What are the motor specifications and what type of control do you need (what will the motor be used for)?
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  3. Jaguarjoe

    Jaguarjoe Active Member

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  4. t_n_k

    t_n_k AAC Fanatic!

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    You would probably better focus attention on protecting the power semiconductors rather than the DC motor - which in terms of over-current is a fairly robust device in comparison to a semiconductor switch.

    Normal practice is to use fast acting fuses for semiconductor protection so using time delay fuses may not be desirable. Perhaps a combination of the two types is required. Alternatively, graded motor protection might be accomplished with an adjustable thermal overload relay of some sort. Depends on your budget and the degree of 'sophistication' required.
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  5. bassplayer142

    bassplayer142 Thread Starter Active Member

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    Thanks for the prompt and helpful replies! I will need to power two motors to drive a tank style robot up a stairs at a 32deg angle. The robot will probably be 20+ lbs.

    The type of motors I am looking at are below with a large gear ratio for higher torque. The H-bridge I am looking into is also shown below. The protection circuitry is just extra stuff to make sure I don't burn anything from mistakes. I haven't decided on a power supply yet so just neglect that for now.

    http://www.robotmarketplace.com/products/0-HG312.html
    http://www.robotshop.ca/cytron-10-30v-30a-single-brushed-dc-motor-controller.html
  6. marshallf3

    marshallf3 Well-Known Member

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    A lot of the power window circuits on automobiles utilize a very fast overcurrent switch on the driving motor.

    Then there are Polyfuses, they work pretty well too.
    http://www.littelfuse.com/data/en/Product_Brochures/EC327-E_Polyfuse_PTC.pdf

    Most standard motor protectors for AC are built into the motor starters themselves and operate both via a magnetic overcurrent and a thermal heating strip. The heating strips are interchangeable to match the motors.
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  7. GetDeviceInfo

    GetDeviceInfo Senior Member

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    Code calls for a 150% FLA rating, be it time delay, non time delay, or circuit breaker.
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  8. Jaguarjoe

    Jaguarjoe Active Member

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    There's code for toy robot motors?
  9. GetDeviceInfo

    GetDeviceInfo Senior Member

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    Sorry, missed the hobby robot thing.
  10. SgtWookie

    SgtWookie Expert

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    The driver unit you're considering most likely contains a VNH2SP30-E IC, which is a fully integrated H-bridge motor driver with PWM.
    Datasheet: http://www.st.com/stonline/books/pdf/docs/10832.pdf

    It will likely be one of the most compact and low weight solutions that you'll find; both pretty important considerations for a robot - not to mention the relative simplicity of integration.

    Marshallf3's Polyfuse suggestion is a very good one. Compact, inexpensive, and automatically resets. You could also use an automotive-type circuit breaker, but it would be larger, heavier, and likely more expensive.
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