# best braking for dc motor control

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Thread Starter

#### reman130488

hi all..
i have a problem with choose braking for dc motor. maybe you can help me for best braking for dc motor.
and i help to find journal about this too
thanks..

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#### Mike

Big motor or small? how fast does it have to stop? Dynamic Braking is a common brake function used

If not look at some drum brakes, Or maybe a zero speed it switch

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#### reman130488

yesterday, i discuss with my university instructor. he suggest me for use regeneratif braking..

i use this topic for final assignment in my university.

i plan use plugging braking because time response rate to zero is fast but with this braking, motor isolation can broke. after that i give solution with field-powerful(with concept filed-weakening controller)..i searching this journal but nothing about field-powerful..
may you can help me??

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#### M Griffin

The "best" value depends on what criteria you consider to be "best". A higher resistance means lower braking torque. A lower resistance means higher braking torque.

I usually select a resistor size which results in a current of no more than full load current (the maximum generated voltage will normally be no more than the applied voltage). If you want more braking torque than that, then you have to decide how much current (and torque) the application can tolerate.

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#### reman130488

but if we use large voltage or current, isolation in motor can broke. I want time respond for braking this motor is zero (maybe can't zero but near to zero). and if we use voltage or current large, maybe motor can't use.

as i know, with field-weakening control we can increased motor speed. If i use this concept to for braking with field-forceful. but this concept only my idea..hehehe..

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#### M Griffin

If you are using dynamic (or regenerative) braking, then the generated voltage at any speed will be the same as the normal operating voltage for that speed. As the speed declines, the generated voltage also declines, which means the current declines, and so the braking torque also declines.

Regenerative braking is essentially the same as dynamic braking, except that the recovered power is pumped back into the power source rather than simply dissipated as heat in a resistor.

As for how long it will take the motor to stop, that also depends on the amount of friction and the load inertia. You would have to measure the motor characteristics to determine it's normal behaviour, and then add in the load characteristics. You will have to get out your elementary physics books to calculate this (I bet you always wondered what that stuff was good for).

I have done all of my DC motor projects with permanent magnet motors, so I haven't tried anything with field weakening (or increasing) control. You should be able to derive the effects of this from standard motor equations.