PSpice Model of DC Motor

[projectstudent]

I am actually working on my final year project and have problems getting a DC Motor from Orcad 16.2 version (PSpice) library, for my H-Bridge circuit test.

I understand this can be modelled separately and incorporated into my H-Bridge schematics. I do know how to mathematically model a DC Motor with the electrical and mechanical considerations and thus its block diagram in turn.

However, I can get the inductor, the resistor components but I do not know from where to get the DC Motor componenet itself or the back emf component or a source voltage with an emf from the library of Orcad 16.2 version.

Can someone help me out on how to get the DC Motor using Orcad version 16.2 or to model a DC Motor, pls!!!

 

[FvM]

To design a motor model, you basically have to consider how the mechanical quantities (rotational speed, torque, inertia) are related to the electrical ones (current, voltage). You should be able to get the fundamental equations from literature if you can't find them from the scratch. Also the load has to be considered of course.

You can implement the model either as an electrical equivalent circuit e.g. using a capacitor to model the inertia or a resistor for friction, or use PSPICE ABM (analog behavioural modelling).

 

[projectstudent]

Thank you but I Already know how to calculate or model dc motor mathematically. All I need is to translate this knowledge into pspice. This ABM, in what version of orcad can I get it? Remember I mentioned orcad version 16.2.

 

[FvM]

Remember I mentioned orcad version 16.2

Yes. Analog behaviour modelling is surely supported in versions 16.2, but possibly not by all licenses.

I suggest a simple equivalent circuit with a capacitor representing the motor and load inertia, a parallel resistor as a simple linear friction modell, and a current source for a constant load torque (if any). Or another resistor for speed proportional load torque. All these elements connected in parallel to the inner motor terminals, rotor inductance and resistance are connected between inner and outer terminals.

 

[projectstudent]

That sounds good and reasonable! I will build that model but can you please sketch the circuit for me to see too.

 

[FvM]

Should look like this

View attachment DC-Motor.pdf

 

[projectstudent]

I am going to send you the result of the pspice simulation and the schematic itself for you to go through and tell me where I went wrong. Can't do it here at uni. Will post it to you as soon as I get home.