# modeling a solenoid coil

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Goutham Sajja on 23 Feb 2021
Commented: Juan Sagarduy on 26 Feb 2021
Hello All,
I am trying to model a solenoid in simscape using the blocks from simscape electrical, mechanical and physical signal blocks. The equation that I have considered is
V = i*R + L*di/dt + i*(dL/dt)
V = voltage, i = current through the solenoid, R = resistance of the coil, L = inductance, dL/dt = dL/dx*dx/dt rate of change of inductance with respect to change in plunger position.
I will be using the force - stroke characteristic data to evaluate dL/dx.
When I rearrange the above equation and solving for i, we get
i = (1/L) * int ( V - (i*R) - i*(dL/dx)*(dx/dt))
When I impliment this particular equation using physical signal blocks and try to simulate it, I am getting the following error:
I kindly request you to guide me to overcome this error.
Thanks and Regards,
Goutham Sajja

Juan Sagarduy on 25 Feb 2021
Hello Goutham
I think you will find creating a Simscape component a better solution. Then, you can write the equations textually.
See link to give u a hint: https://se.mathworks.com/videos/simscape-language-electronic-example-73114.html
Best Regards Juan
Goutham Sajja on 25 Feb 2021
Edited: Goutham Sajja on 25 Feb 2021
Hello Juan,
I did try to create a custom Simscape component. I considered adding an additional input to the PS Subtract block. But when I try to simulate it, I am getting the following error:
Thanks
Goutham Sajja
Juan Sagarduy on 26 Feb 2021
Hello Goutham
I attach a ssc implementation of a dynamic inductance, pretty much as described in the snapshot. You will see how this is done, I use the inductor in the Foundation Library as a base to create the ssc in the attachment.
We have a 1-day course on Simscape that you may find interesting to attend and give you a rounded insight on physical network modeling. See link:
Best of Luck
Juan

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