Thermal relay - QuickField simulation example
The thermal relay is attached to the tank with a hot liquid. Relay winding conductivity depends on temperature. With temperature raise the conductivity, current and electromagnetic force fall down.
How to find temperature effect on relay winding conductivity?
Answer Typical applications Geometry
Given
Solution
Results
The tank is cooling down. Calculate the relay switching temperature and time.
Engineering question
Set up an axisymmetric QuickField Transient Magnetics problem for a thermal relay winding and evaluate temperature-dependent conductivity effects from computed field results.
thermal protection relays, relay windings, temperature-sensitive relays
Download
Simulation problem
Problem Type
Axisymmetric problem of transient magnetics.
Magnetic permeability of core μ = 400;
Voltage U = 12 V;
Spring force f = 0.8 H
Initial temperature T1 = 200 °C;
Ambient temperature T0 = 20 °C;
Time constant ts = 10 hrs;
Conductivity of copper σ - depends on temperature:
The temperature falls down as
T(t) = T0 + (T1-T0)·exp( -t / ts).
The integration time was chosen to be 3ts, integration step ts/5.
To calculate the electromagnetic force as a function of time transient magnetic problem is simulated. The temperature function T(t) was added to the material properties of 'winding' block.
After 16 hours the temperature falls down to 56°C and relay switches off.
Related examples