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Variable RL

Owned by Sylvain Ménard
Apr 23, 2024
2 min read

This block implements a serial variable RL.

The model consists of a controlled current source in parallel with an RC snubber. The value of the generated current is determined by the voltage measured across it, the resistance, and the inductance, the latter are sent as an input.

 

Model Formulation

The voltage across a serial variable RL is the sum of the voltage drop across the resistance (Ohm’s law) and the induced voltage due to magnetic flux variation (Faraday's law), determined by the equation:

Since the self-inductance is the ratio between magnetic flux and the current:

thus,

It is considered that the voltage drop related to the change of inductance is negligible as compared with the drop from the change of current.

The discretization of equation above results in:

Finally,

The current through the inductance is the state variable and its initial value is a parameter of the block, the Initial current (I0).

Parameters

Parameters

 

Resistance (R)

Variable resistance value in ohm (Ω). Can be set to be an input or a constant.

Indutance (L)

Variable inductance value in henry (H). Can be set to be an input or a constant.

Initial Current (I0)

Initial current in amperes (A)

Maximum current (Imax)

Maximum saturation current in amperes (A)

Snubber resistance (Rsn)

Snubber resistance value in ohm (Ω).

Snubber capacitance (Csn)

Snubber capacitance value in farad (F).

 

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