Author Topic: Motor driver current rating  (Read 879 times)

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Offline init

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Motor driver current rating
« on: April 27, 2016, 03:40:43 pm »
I'm looking at putting a 12V DC motor with worm drive into a project I'm doing. It has a load current up to 7.5 A and a stall current of 31A. From a design perspective, I want to drive this motor with a H-bridge or two half bridge chips. Should I specify the chip current rating at the stall current or below? Do these chips usually have a stall current rating on top of operational current?
 

Online ataradov

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Re: Motor driver current rating
« Reply #1 on: April 27, 2016, 03:58:41 pm »
Drivers typically specify continuous operational current and short-time overcurrent (typically for 10-100 ms).

If there is a chance your motor will stall, you need to add stall detection and disable the driver in case if motor is stalled. Motors don't like to be stalled for too long.

That's a very generic description. There can be other vital details, like start current, which will be higher than nominal operational current and you need to account for that as well.
Alex
 

Offline init

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Re: Motor driver current rating
« Reply #2 on: April 27, 2016, 04:29:47 pm »
Drivers typically specify continuous operational current and short-time overcurrent (typically for 10-100 ms).

If there is a chance your motor will stall, you need to add stall detection and disable the driver in case if motor is stalled. Motors don't like to be stalled for too long.

That's a very generic description. There can be other vital details, like start current, which will be higher than nominal operational current and you need to account for that as well.

More specifically, I want a motor that can handle long static torque periods such as those used in a robot. Imagine holding a weight out perpendicular to your body and keeping it still, then shift it up above your head and hold it still - I want a motor that is suited to this kind of function. Assuming the amount of static torque required isn't huge (less than rated torque), does this mean the stall current will be less in any way?
 

Online ataradov

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Re: Motor driver current rating
« Reply #3 on: April 27, 2016, 04:37:40 pm »
More specifically, I want a motor that can handle long static torque periods such as those used in a robot.
Then DC motors is not what you want unless you want to deal with encoders and design a proper servo controller. It is not a trivial task.

Assuming the amount of static torque required isn't huge (less than rated torque), does this mean the stall current will be less in any way?
I would go with stepper motors in this case. Way easier to control and their normal holding torque should be sufficient provided good mechanical design.
Alex
 


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