how do you model a motor in LT spice

[large_ghostman]

hi,
how do i model a 12V 1.2A motor in LT spice? i am guessing i have to use an inductor as the motor is a inductive load, but how do i work out what size inductor and do i need to add anything other than a inductor (i know about adding flyback diode i am just asking about to model a motor)

 

[misterT]

I like this model very much:

http://www.ecircuitcenter.com/Circuits/dc_motor_model/DCmotor_model.htm

I hope the website explains the details. If not, ask.

It is difficult to say what is the inductance of you motor winding etc. You need to measure the component, if you do not have a datasheet. You need total of 6 parameters to properly simulate an electric motor. The website has an example table of these parameters.

 

[large_ghostman]

wow! thank you very much! a silly question but to measure the motor inductance do i simply hook up the LCR meter to the leads with the motor disconnected from everything? i know it sounds like a really silly question but i havnt done any inductance stuff with the meter yet

 

[large_ghostman]

that is a brilliant site! it will take me a while to grasp it all especially the mechanical side but is a really great way to sim a motor! i am in luck and i know there is a datasheet for the fan i want to use! so i should be able to use real values, only just learning LTspice and already getting some results that i didnt expect so i will have to go through some simple tutorials to get the hang of it

 

[misterT]

To measure the motor inductance do i simply hook up the LCR meter to the leads with the motor disconnected from everything?

Yes. Disconnect the motor and make sure that the motor can't spin. Then try measuring from different positions (turn the shaft to different angle).. take an average of the measurements or something like that.. or the "best" measurement. It may give wrong measurement at some angles. Not sure.

 

[large_ghostman]

I should have mentioned it is a BDLC with all the control stuff inside, sorry for leaving that bit out, i will give it a try anyway! i have tried the motor for real and taken measurements but i am trying to learn spice so i thought i would sim it and see how close it gets

 

[misterT]

I should have mentioned it is a BDLC with all the control stuff inside, sorry for leaving that bit out, i will give it a try anyway! i have tried the motor for real and taken measurements but i am trying to learn spice so i thought i would sim it and see how close it gets

Then this paper might help you: http://support.ctc-control.com/customer/elearning/younkin/motorParameters.pdf

 

[large_ghostman]

thats useful for a couple of things, because my maths is weak i am learning maths via another maths forum and they ask for examples of what i am trying to learn, so that will be good for getting this kind of info! once i understand the maths a bit better that will be very useful thank you!