# Solenoid design

Discussion in 'The Projects Forum' started by Jitesh, Nov 11, 2010.

1. ### Jitesh Thread Starter New Member

Nov 11, 2010
3
0
Hi all,
I want to design an electrical contactor, for which the first step would be the design of the solenoid plunger assembly. I have information about the coil voltages (the pick-up and hold voltages), the currents allowed to flow through the coil, and the time required to close and open the contacts. I dont know where to start the design process from.
Also, what should be the shape of the magnetic core? I have seen cores with "U" and double "E" shapes, with the coil wound on the middle leg.
Any help will be appreciated.

Thanks
Jitesh

2. ### wayneh Expert

Sep 9, 2010
14,799
5,287
How married are you to making your own? Any old VCR or tape-based answering machine will likely have several small solenoids in it. Far easier to pull one than to roll your own. Making thousands of turn of wire is tough on the hands, eyes, etc.

3. ### Jitesh Thread Starter New Member

Nov 11, 2010
3
0
Hi,
But the thing is, I wont be rolling out the coil assembly. I just want to design on paper and want to validate the design using a simulation program. I am required to design the thing from scratch because there are specific requirements for the closure time and other variables mentioned.
Just want to know the starting point and how to go about designing a solenoid plunger.

Thanks,
Jitesh

4. ### wayneh Expert

Sep 9, 2010
14,799
5,287
You'll want to learn about the Wheeler formula for computing inductance from coil geometry.
http://www.electrondepot.com/electrodesign/Wheeler-s-1982-formulas-verified-74291-.htm
Then you'll want to have a wire table for getting the properties of copper wire at every gauge. You'll need this to relate the physical dimensions to the number of turns and the DC resistance, ie. to fill in the parameters to the Wheeler formula.
http://www.superioressex.com/MagnetWire/Engineering_Data_Handbook.aspx
Somewhere I can recall seeing the optimal coil cross section to minimize the copper for a maximum field.
http://www.netdenizen.com/emagnet/solenoids/solenoidonaxis.htm
It's nearly square, I think, meaning depth and length are roughly equal, but I think depth is a bit less than length for an ideal solenoid.

5. ### Jitesh Thread Starter New Member

Nov 11, 2010
3
0
Thanks for the good amount of data made available.