Author Topic: DC motor driver output current  (Read 1593 times)

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Offline kevinthesunTopic starter

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DC motor driver output current
« on: March 02, 2014, 10:42:58 PM »
Should the DC motor driver have the maximum output current higher than the stall current of the motor, or just higher than the maximum power current?

For example AndyMark 9015 Motor has following features:
Performance Specs:

    Voltage: 12 volt DC
    No load RPM: 16,000
    Free Current: 1.2 amps
    Maximum Power: 179 Watts at 32.5 amps
    Stall Torque: 60.64 oz-in (428 m-Nm)
    Stall Current: 63.8 amps

It seems difficult to find a motor driver which has a 32.5 amps output current.
« Last Edit: March 02, 2014, 11:23:32 PM by kevinthesun »

Offline bdeuell

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Re: DC motor driver output current
« Reply #1 on: March 03, 2014, 02:25:13 AM »
Often you want to select a motor controller that can handle the max stall current but this is not always necessary under the right circumstances. If you plan to use a motor controller rated at a lower than stall current it is highly recommended to have some sort of current limiting or protection to prevent damaging the controller (I have seen what can happen without this protection ... it isn't pretty). If you are absolutely certain your load will not never stall your motor then it is possible to operate without this protection, but this is not usually a safe assumption for robotics.

Motor controllers are often given two current ratings one for continuous operation and one for transient operation. The transient rating should exceed your stall current, thermal protection of the controller can help prevent a continuous stall condition from damaging the controller. The required continuous operating current depends on your application and expected loads, motors often have a current-torque curve or constant that describes this relationship.

Some motors will also give a max operating current that is less than the stall current, (this is the max continuous operating current of the motor to prevent overheating) it may be desirable to have a current limiting controller to prevent damage to the motor.

As for the maximum power current, I suspect this is describing a point in the motors operating range that provides the highest power output. This is useful for optimizing the design of a system as it may be desirable to operate at this point. However they could be describing the max continuous operating specs ... without a real datasheet it is not always clear what they are intending to convey ... even with a data sheet it is not always clear. you could contact the manufacture/distributor for a clarification of this spec.

Offline jwatte

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Re: DC motor driver output current
« Reply #2 on: March 03, 2014, 11:25:03 AM »
Is this brushed or brushless?

For brushed DC motors, there are a number of high-power motor controllers to choose from. Dimension Engineering makes the Sabretooth, and Orion Robotics makes the RoboClaw. Both come in versions that may work for you (they have built-in overcurrent protection.)

Offline kevinthesunTopic starter

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Re: DC motor driver output current
« Reply #3 on: March 03, 2014, 01:53:30 PM »
Thank you for your help! :D


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