Generating using a DC brushed motor

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Discussion Overview

The discussion revolves around the feasibility and calculations involved in using a DC brushed motor as a generator by mechanically turning its shaft to produce electricity. Participants explore the technical aspects of power generation, including efficiency and output characteristics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the calculations needed to determine the potential power output when using a DC brushed motor as a generator.
  • Another suggests examining the motor's specifications during normal operation, particularly the input current at a specified voltage, to estimate the output current when generating electricity.
  • It is noted that motors are generally efficient, and a slight derating of the motor's specifications may be necessary to estimate generator performance.
  • A participant warns about the noisy output of DC motors due to flyback impulses and recommends implementing a snubber/filter circuit to stabilize the output voltage.
  • One participant questions whether a brushless DC motor could be a better alternative to avoid issues with noisy output.
  • Another participant points out that using a brushless DC motor may require a more complex control system.

Areas of Agreement / Disagreement

Participants express differing views on the suitability of brushed versus brushless DC motors for generating electricity, indicating that multiple competing perspectives exist regarding the best approach.

Contextual Notes

There are unresolved assumptions regarding the efficiency of the motors and the specifics of the control systems required for brushless motors. The discussion does not reach a consensus on the optimal motor type for generating electricity.

Who May Find This Useful

This discussion may be of interest to individuals exploring alternative energy generation methods, hobbyists working with motors, and those involved in electrical engineering or robotics.

lucy_b14
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Good Evening

I'm interested in the possibility of using a DC brushed motor as a generator (ie running it in reverse - mechanically turning the shaft to produce electricity).

However, I have no idea how to calculate the power I could potentially achieve. Any tips or equations in particular would be greatly appreciated.

Thanks
 
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lucy_b14 said:
Good Evening

I'm interested in the possibility of using a DC brushed motor as a generator (ie running it in reverse - mechanically turning the shaft to produce electricity).

However, I have no idea how to calculate the power I could potentially achieve. Any tips or equations in particular would be greatly appreciated.

Thanks

A good start would be to look at the specifications for the motor's normal operation. What is the input current listed for the specified DC input voltage? That will give you a pretty good ballpark idea of what the output current will be when you are turning the motor fast enough to generate the specified voltage. Motors are pretty efficient, so you may only have to derate the motor numbers by a couple tens of percent to get the generator numbers.

Be sure to calculate the associated powers, so you know what kind of input mechanical power will be required to get that output electrical power.
 
Oh, and the output of DC motors is generally pretty noisy, due to flyback impulses when the brushes are switching. Be sure to plan on an output snubber/filter circuit to clean up the DC output voltage.
 
Please excuse me if this comment is stupid, but would it not be possible to use a brushless DC motor - and then there wouldn't be an issue of a noisy output signal ?
 
Ah, You need a more complex control system to run a brushless dc motor correct ?
 

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