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RL circuit simulation problems in proteus

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shaolinyo

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hello , i need help please,

i simulate simple RL circuit in proteus but it give wrong values , values differrent from the theoretical carlculation

Capture1.JPG
cap3.JPG
cap2.JPG

the voltage across inductor when the switch is open sould be 110 v but proteus give 5V

but using pspice it gives result near the theoretical result

p1.JPG
p2.JPG

i want to know what is the problem of proteus simulation
thank you
 

Hi,

You simulate two different situations:
* pulse is 5V (low impedance) / 0V (low impedance)
* switch closed = 5V (low impedance) / open = high impedance.

Why don't you simulate identical circuits?

Klaus
 

hi , how i can specify high impedance in the proteus , i need it in proteus because i will use microcontroller to generate the pulse (close switch , open switch) its for a project for metal detecting

thank you
 

I guess you want to design a real circuit with real switching elements like MOSFET. There's no problem to simulate it with any circuit simulator, either Proteus or PSPICE.
 

thank you , what u think about howlland current source can it offer the require high impedance as the switch is open?
 

hello , i used diode to simulate the high impedance when the switch is open , i get the same result , i really thing that there is problem with proteus simulation of inductor
rt.JPG

please help
 

Hi,

i get the same result
Click to expand...
Please give unambiguos informations:
* "same" as before
* "same" as with the other tool?

Klaus
 

An inductor tries to continue flow of current when shut off suddenly. Often it generates a spike, and sometimes it's high voltage.

Your schematic is hard to predict what Ampere levels flow in each branch. When the pulse drops to 0V, the inductor probably continues to pull current through the diode for a while (besides pulling current around the loop with the resistors). The simulation should show these things happening. Your timeframe needs to be the right length, so that all momentary behavior is visible.
 

i used diode to simulate the high impedance when the switch is open , i get the same result , i really thing that there is problem with proteus simulation of inductor
Click to expand...
Just expectable. The diode is forward biased during the interval of interest, it can't "simulate the high impedance".

Referring to the original question, Proteus doesn't have the PSPICE specific time controlled on- and off-switch model, but it has the generic SPICE voltage controlled switch, look for VSWITCH under modelling primitives. You may use it to learn that the problem isn't Proteus related but caused by using different simulation circuits.

As for the real design problem, you should specify the intended voltage and current range and use a suitable switching device. Questioned Howland current source is limited to the supply voltage range (reduced by the shunt voltage drop and amplifier saturation voltage). Hardly giving 100V compliance with regular OP.
 

Hi

I wonder why some people have simulation tools, but don't use them.
It's so simple to measure the diode current and the diode voltage.
If there is voltage and current, then it can't be high impedance...

Klaus
 

thank you,
but the diode is not forward biased when the pulse go to 0 , it block the current generated from the inductor
the voltage accross the inductor at the discharge time should be spike of 110 v but proteus show 5v that is the problem
 

Hi,

Indeed it's all already explained.
but the diode is not forward biased when the pulse go to 0
Click to expand...
What makes you sure about that? Your knowledge or the test results?

Again:
* measure the diode current
* measure the diode voltage
* additionally measure the inductor voltage

Show us the test results and explain how they explain your statement.

Klaus
 

ok i send the result with the circuit , i'm a beginner in electronic so please see if u can help me about that , or simulate the circuit on your proteus to check , thank you
r1.JPG
r2.JPG
r3.JPG
 

but the diode is not forward biased when the pulse go to 0 , it block the current generated from the inductor
the voltage accross the inductor at the discharge time should be spike of 110 v but proteus show 5v that is the problem
Click to expand...
Error of reasoning. The diode is forward biased by the inductor current and clamps R2 voltage to -0.7V.
 

hello FvM so how i can make the diode to block the the inductor current ?
 

A diode can't block the inductor current, you need a controlled switch as already mentioned.
 

Hi,

ok i send the result with the circuit
Click to expand...
Whether a diode is forward biased or not you can see with the diode voltage. Don´t you agree?
I twice asked you to measure this. You didn´t show this "result". Maybe you measured it.

I hope you now understand what happens... and why the voltage is limited. (and that the simulation result for the given circuit is correct)

hello FvM so how i can make the diode to block the the inductor current ?
Click to expand...
Difficult/impossible with your setup. What modifications can you accept?

Maybe have a look at a typical "boost converter circuit".

Klaus
 

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