Thermal Resistor

Resistor with thermal port

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  • Thermal Resistor block

Libraries:
Simscape / Foundation Library / Electrical / Electrical Elements

Description

The Thermal Resistor block represents a temperature-dependent resistor. When the temperature at the thermal port is T, the resistance is

R=R0(1+α(T−T0))

where:

  • R0 is the nominal resistance at the reference temperature T0.

  • α is the temperature coefficient.

The following equation describes the thermal behavior of the block:

Q=KdtcdTdt−i2R

where:

  • Q is the net heat flow into port H.

  • Kd is the Dissipation factor parameter value.

  • tc is the Thermal time constant parameter value.

  • dT/dt is the rate of change of the temperature.

  • i is the current through the resistor.

The product of dissipation factor and thermal time constant is the thermal mass of the resistor. In certain applications, it is more convenient to define the thermal mass as a product of mass and specific heat capacity of the resistor, the same way as in the Thermal Mass block. Use the Thermal mass parameterization parameter to select between these two parameterization methods.

Variables

To set the priority and initial target values for the block variables prior to simulation, use the Initial Targets section in the block dialog box or Property Inspector. For more information, see Set Priority and Initial Target for Block Variables.

Nominal values provide a way to specify the expected magnitude of a variable in a model. Using system scaling based on nominal values increases the simulation robustness. Nominal values can come from different sources, one of which is the Nominal Values section in the block dialog box or Property Inspector. For more information, see Modify Nominal Values for a Block Variable.

In particular, the Temperature variable lets you set a high-priority target for the temperature of the thermal resistor at the start of the simulation. The default value is 300 K.

Ports

Conserving

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Thermal conserving port that provides the resistor temperature.

Electrical conserving port associated with the resistor positive terminal.

Electrical conserving port associated with the resistor negative terminal.

Parameters

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The nominal resistance of the thermistor at the reference temperature. Many datasheets quote the nominal resistance at 25°C (298.15 K) and list it as R25.

The temperature at which the nominal resistance was measured.

The coefficient α in the equation that describes resistance as a function of temperature.

How to define thermal mass:

  • Specify time constant and dissipation factor — Use the product of thermal time constant and dissipation factor. This method is useful when modeling thermistors.

  • Specify mass and specific heat capacity — Use the product of mass and specific heat capacity. This method is convenient when you intend to use the block as a resistive heating element.

The time it takes the resistor temperature to reach 63% of the final temperature change when a step change in ambient temperature occurs.

Dependencies

To enable this parameter, set Thermal mass parameterization to Specify time constant and dissipation factor.

The thermal power required to raise the thermal resistor temperature by one K.

Dependencies

To enable this parameter, set Thermal mass parameterization to Specify time constant and dissipation factor.

Mass of the resistor. The mass is constant during simulation.

Dependencies

To enable this parameter, set Thermal mass parameterization to Specify mass and specific heat capacity.

Specific heat capacity of the resistor material.

Dependencies

To enable this parameter, set Thermal mass parameterization to Specify mass and specific heat capacity.

Extended Capabilities

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C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2016a

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See Also

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