Solenoid simulation for force, stroke and coil heating
Know how much force a solenoid produces at every point of its stroke, how hot the coil runs at its duty cycle, and which plunger, frame or winding changes would give more force or a smaller package.
A solenoid’s force changes sharply over its stroke. It is usually weakest with the plunger fully out, where the air gap is largest, and rises steeply as the gap closes. Saturation in the plunger, the pole piece or a thin section of the frame can then cap that force well below what a simple magnetic circuit estimate suggests.
More about solenoid simulation
Solenoid simulation solves the magnetic field through the coil, plunger, frame and air gap at a series of plunger positions. The result is a force-stroke curve for each current or voltage you specify, alongside the flux density in the steel, so saturated regions are visible. Coil losses then go into a thermal model to give the winding temperature at your duty cycle and ambient, and the inductance at each position shows how quickly current, and therefore force, builds when the coil is energised.
Plunger tapers, pole-face profiles, frame thicknesses and winding options can be compared in one study, each with its own force-stroke curve and coil temperature.
Typical products: valve actuators, fuel and hydraulic solenoids, door locks and latches, relays and contactors, pinch valves and automotive and industrial actuators.
What a solenoid study tells you
Is there enough force at the start of the stroke?
Force at the fully open position, where it is usually lowest, compared with the spring preload, friction and the load the actuator has to move.
Can the force-stroke curve be shaped?
How a conical or stepped plunger, a tapered pole piece or a stop collar flattens or steepens the curve to suit the load.
Where is the steel saturating?
Flux density through the plunger, pole piece and frame, showing which sections limit force and where extra material would help.
How hot does the coil get?
Winding temperature at your duty cycle, supply voltage and ambient, set against the insulation class of the wire and bobbin.
How quickly will it respond?
Inductance across the stroke, which sets how fast current rises after switch-on and so how soon the plunger starts to move.
Will a reduced holding current be enough?
Closed-position force at reduced current, for drives that pull in at full current and then hold at a lower one to save power and heat.
What we model
Magnetostatic force
Force on the plunger at each position and current, from the full field solution including fringing and leakage flux.
Non-linear steel
B-H curves for the plunger, frame and pole materials, so saturation is captured rather than assumed away.
Coil design
Turns, wire size, fill and resistance traded against force, power and temperature for a given supply.
Coil heating
Copper loss applied as a heat source in a thermal model of coil, bobbin, frame and mounting, for continuous or intermittent duty.
Proportional solenoids
Force held close to constant over the working stroke at each current, for proportional valves and actuators.
Latching and permanent magnet designs
Holding force with the coil off, and the current needed to release or switch a latching solenoid.
Before you start
What to send us
- CAD of coil, plunger, frame and pole pieces (STEP or native)
- Stroke length and the force required at key positions
- Supply voltage or current, and how the coil is driven
- Coil details: turns, wire size and resistance, if already set
- Steel grades or B-H data for the magnetic parts
- Duty cycle, ambient temperature and mounting arrangement
Can you include the return spring and the load?
Spring and load forces are set against the magnetic force across the stroke, which shows where the margin is smallest.
Do you need B-H data for the steel?
It gives the most reliable force figures, particularly near saturation. If you only know the grade, we use representative data for it and say so in the results.
Can you simulate AC solenoids?
Yes. AC operation brings eddy currents and a force that pulses at twice the supply frequency, and the study shows how a shading ring affects the holding force.
Can you design the coil as well as analyse it?
We can size turns and wire for a given supply and temperature limit, and supply the winding specification with the frame and plunger drawings.
Send us your solenoid
