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Relay dynamics simulation using Libre Office (Open Office) and Parametric Object Interface - QuickField simulation example

Relay-plunger motion under electromagnetic and spring forces, with LibreOffice used to integrate the mechanical motion while field force varies with position..

To combine the electromagnetic field analysis with the moving core dynamics both LibreOffice and LabelMover are used. Interaction between LabelMover and LibreOffice is performed using application programming interface (API).

Engineering question

How to calculate the relay's plunger motion using QuickField and LibreOffice via LabelMover?

Answer
Set up an axisymmetric QuickField DC Magnetics problem and replace the multi-turn coil with an equivalent total current. Use LibreOffice (via the LabelMover API) to integrate the plunger's equation of motion, calling LabelMover at each step to get the electromagnetic force.

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Typical applications
electromagnetic relays, relay armatures, electromechanical switching devices

Relay dynamics simulation using Libre Office (Open Office) and Parametric Object Interface

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Simulation problem

Problem Type
Axisymmetric problem of DC magnetics.

Geometry
Relay dynamics simulation The electromagnetic and spring forces act on the plunger. Both forces depend on the plunger position Coil Plunger Spring 20 mm x Ø 7.2 mm

Given
Current I = 400 Ampere*turns;
Plunger pull-out position xmax = 10 mm.
Plunger pull in position xmin = 6 mm.
Plunger weight m = 4.5 g;
Spring constant k = 4 N/m
Spring free position xspring.free = 15 mm.

Task
Relay-plunger motion under electromagnetic and spring forces, with LibreOffice used to integrate the mechanical motion while field force varies with position..

Solution
The multi-turn winding is replaced with the equivalent total current.

The motion function can be found from second-order differential equation
m · d²x/dt² = f(x),
where m - is a plunger weight (kg),
x - is a plunger position (m)
f(x) - is the force acting on the plunger (N).
The force acting on the plunger is a sum of spring force fspring(x) = k·(xspring.free - x) and electromagnetic force.

The equations are solved in LibreOffice VBA. The dynamic link is used to invoke QuickField and calculate the electromagnetic force at each step.

The calculations are stopped when x=xmin (pull in position, plunger hits damper).
LibreOffice VBA to QuickField LabelMover link The equations are solved in LibreOffice. The dynamic link is used to invoke QuickField LabelMover and calculate the electromagnetic force at each step LibreOffice VBA QuickField + LabelMover Initial conditions x0 = xmax, v0 = 0 m/s Invoke LabelMover to calculate Force(xi) vi+1 = vi + Force/mass*Δt xi+1 = xi + vi+1* Δt x>xmin ? true false EXIT

Results
The plunger hits initial position between 11th and 12th steps (0.055 - 0.06 s).
LabelMover plot of the plunger position in meters vs time in seconds.

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