Measuring a DC motor's inductance

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Discussion Overview

The discussion revolves around methods for measuring the inductance of a 12V DC motor, comparing various techniques including dedicated instruments like LCR meters and experimental approaches. It also touches on the implications of these measurements for digital controller design.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • Some participants suggest that dedicated instruments like LCR meters generally provide better and more consistent results when used within their limits.
  • Others argue that using experimental methods to measure inductance can be more educational, and propose comparing results from both methods.
  • One participant questions the purpose of measuring inductance, suggesting that if the goal is to create a digital controller, there may be more efficient methods, such as measuring the z-transformed transfer function directly.
  • A later reply reiterates the importance of understanding the purpose behind measuring inductance, particularly in the context of digital control systems.
  • Another participant expresses interest in the z-transform of transfer functions and requests further clarification or resources on the topic.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the best method for measuring inductance, and there are multiple competing views regarding the purpose and implications of these measurements for control system design.

Contextual Notes

Limitations include the potential variability in measurement accuracy between different methods and the dependence on the specific application of the inductance measurement in control systems.

Who May Find This Useful

This discussion may be useful for individuals interested in electrical engineering, control systems, and experimental methods in measuring electrical properties of motors.

bbq_build
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In general - a dedicated instrument will yield better results when used within it's limits ( and more consistent). But to measure a hobby motor, doing the experimental approach, using the techniques would be more educational. Given the two methods I would be tempted to do both and see how close they come out.

If you have access to an LCR meter, it would of course be faster, more convenient.
 
bbq_build said:
If I want to measure the inductance of a 12V DC motor . . . .
Why do you want to measure? What's the purpose?

Say you going to make a digital controller for this motor. Having measured L and R, you will have to z-transform a transfer function, taking calculation time delay in the controller into consideration, and so on. If that's the case, there is smarter way, measuring the z-transformed of the transfer function directly.

Please respond if interested.
 
Hesch said:
Why do you want to measure? What's the purpose?

Say you going to make a digital controller for this motor. Having measured L and R, you will have to z-transform a transfer function, taking calculation time delay in the controller into consideration, and so on. If that's the case, there is smarter way, measuring the z-transformed of the transfer function directly.

Please respond if interested.

Please, I'm currently working on a project on centrifuge modeling, and my supervisor has mentioned to me, what you are saying on converting the open-loop transfer function to z transforms. Can you kindly shed light on 'why' the transfer function should be converted to z transforms? Or I'll appreciate if
you can refer me to any material that'd be of help. Thanks
 

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