Electronics > Beginners
Is this a valid method to measure the inductance of a brushed DC motor?
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fishandchips:
Thanks. In this case, do you think the methods presented in:

http://www.dos4ever.com/inductor/inductor.html and
https://electronics.stackexchange.com/questions/182116/whats-the-easy-way-to-measure-a-dc-hobby-motors-inductance

may not be suitable to measure the inductance of a 12V DC motor? I am trying to get the inductance for modelling in simulink. Is it better to get a LCR meter instead? I am trying to save some money but if it is more accurate and easier to get the inductance using a LCR meter, maybe I have to buy it.

qibeike:
Hey, did you find a way to measure the inductance of the motor? I'm trying to model in simulink an electric vehicle too and I need the internal inductance of the motor.

Thanks in advance.
rstofer:
The method is valid even if the frequency seems over the top.

Measure the DC resistance of the winding.  Then add a series resistor that will make the motor + resistor value match the generator output - probably 50 Ohms.

Apply a signal, perhaps a couple of volts and measure the current by reading the voltage across the external resistor.  From the voltage and current you get total impedance.  You know the two resistances (motor + external resistor in series) so all you need to do is get the inductive reactance and then solve for L which is a function of frequency.

http://support.ctc-control.com/customer/elearning/younkin/motorParameters.pdf

Page 4 talks about it...

I'm not sure if the numbers will make any sense.  Try a few frequencies and see how it turns out.  When I was playing with a DC motor simulation, I just picked 80 uH and called it good.  It's far more important that your model tracks the physical constants of the motor.  These may need to be measured with a tachometer, voltmeter and ammeter.

https://web.stanford.edu/class/me161/labs/Lab06MotorConstants.pdf
 
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