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Thermal Resistor - Model resistor with thermal port

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Passive Devices

Description

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

where:

• Q is the net heat flow into port A.

• K_d is the Dissipation factor parameter value.

• t_c is the Thermal time constant parameter value.

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

Dialog Box and Parameters

Electrical Tab

Nominal resistance

The nominal resistance of the thermistor at the reference temperature. Many datasheets quote the nominal resistance at 25°C and list it as R25. The default value is 1 Ω.

Reference temperature

The temperature at which the nominal resistance was measured. The default value is 25 °C.

Temperature coefficient

The coefficient α in the equation that describes resistance as a function of temperature. The default value is 5e-05 1/K.

Thermal Tab

Thermal time constant

The time it takes the resistor temperature to reach 63% of the final temperature change when a step change in ambient temperature occurs. The default value is 10 s.

Dissipation factor

The thermal power required to raise the thermal resistor temperature by one K. The default value is 0.001 W/K.

Initial temperature

The temperature of the thermal resistor at the start of the simulation. The default value is 25 °C.

Ports

The block has the following ports:

A

Resistor thermal port.

+

Positive electrical port.

-

Negative electrical port.

See Also

Thermistor, Thermocouple.

Timer

Thermistor

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