Resistor (thermal)

Resistor whose losses heat its thermal port and whose resistance changes with its temperature.

  • electrical
  • thermal
  • Modelica Standard Library
  • 3 ports
  • 3 parameters
BlockResistor (thermal)KindheatingResistorLibraryElectrical

Description

A linear resistor with a thermal port. Its resistance changes linearly with the port temperature, and all of its electrical loss flows out of the port as heat.

Use it to couple an electrical circuit to a thermal model, for example a heater or a winding that warms up.

Example

Battery, supercapacitor, and a heating load A battery cell heats a temperature-dependent resistor while a power sensor measures it, and a supercapacitor charges at 1 A.

Cell 4.2 VPowerHeater 4 ΩBody 100 J/KBody temperatureGroundSupercap 1 FCharger 1 Av supercapGround (supercap)
In Gradara, select a Resistor (thermal) block and press F1, then choose Open example. It opens as a new model in My models, ready to run.

Also in this example:Voltage sensorGroundHeat capacitorTemperature sensorDC currentBatterySupercapacitorPower sensor

Ports

Conserving terminals 3

  • heatheatPortthermal

    Thermal port. Its temperature sets the resistance; the loss power leaves through it.

  • +pelectrical

    Positive pin. Current into p is counted as positive.

  • −nelectrical

    Negative pin.

Parameters

  • Resistance at T_refR1 Ω

    ≥ 0

    Resistance at the reference temperature, in ohms. 0 or more.

  • Reference temperatureT_ref300.15 K

    ≥ 0

    Reference temperature, in kelvin, at which the resistance equals R.

  • Temperature coefficientalpha0.0039 1/K

    Linear temperature coefficient, in 1/K. The default 0.0039 is close to copper; 0 gives a constant resistance.

Equations

Modelica
v = p.v − n.v, i = p.i, p.i + n.i = 0
R_actual = R · (1 + alpha · (heatPort.T − T_ref))
v = R_actual · i
heatPort.Q_flow = −v · i

Implementation

Modelica Standard Library 4.1.0Modelica.Electrical.Analog.Basic.Resistor
MSL documentation

Assumptions and limitations

  • The simulation stops with an error if 1 + alpha · (heatPort.T − T_ref) falls to 0 or below.
  • Linear temperature dependence only; no inductance or thermal mass of its own.

Tips

  • The heat port must be connected. Attach a Heat capacitor for the resistor’s own thermal mass, or a Fixed temperature to hold it constant.

Used in

These larger examples use it too. Open them from Examples in the app.

  • Data center cooling control

See also

Select a block in Gradara and press F1 to open its page offline.