Discharging inductivity - transient state

Electrical circuit is built with:
• voltage source E
• resistor R
• switches X1, X2
• inductivity L

discharging inductivity - electrical circuit

Switch X2 is being closed and switch X1 is being opened, both switches change their state in the same time. As a result inductivity discharging current i(t) starts to flow in circuit. Immediately after closing the switch X2 the transient state occurs in electrical circuit, therefore, commutation principles have to taken under consideration. Kirchhoff's voltage law equation will be written for circuit. General formula for inductivity's voltage will be taken under consideration.

discharging inductivity - Kirchhoff's voltage law Formula for - inductivity voltage

instantaneous voltage and instantaneous current

Kirchhoff's voltage law equation will be rewritten to create differential equation.

discharging inductivity - Kirchhoff's voltage law

Differential equation with separated variables which has to be solved. To solve this differential equation substitution method will be applied.

discharging inductivity - differential equation discharging inductivity - differential equation

Inductivity's discharging current

After solving differential equation a relation for inductivity's current iL(t) is obtained. Formula is related to inductivity discharging time's transient state. Inductivity discharging circuit's time constant appears in formula → T=L/R.

inductivity's current i_L(t) during inductivity discharging

Inductivity's discharging voltage

To obtain formula for inductivity's voltage uL(t) a derivative of inductivity's current has to be computed → uL(t)=L·diL(t)/dt. Formula is related to inductivity discharging time's transient state. Inductivity discharging circuit's time constant appears in formula → T=L/R.

inductivity's voltage u_L(t) during inductivity discharging

Inductivity's discharging current - time characteristic

Inductivity's discharging current iL(t) received from simulation for following elements values:
• voltage source E=12V
• resistor R=1kΩ
• inductivity L=1mH

inductivity's current i_L(t) during inductivity discharging - time characteristic

Inductivity's discharging voltage - time characteristic

Inductivity's discharging voltage uL(t) received from simulation for following elements values:
• voltage source E=12V
• resistor R=1kΩ
• inductivity L=1mH

inductivity's voltage u_L(t) during inductivity discharging - time characteristic