Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Why inductance is changing, shouldn it be constant?

Status
Not open for further replies.
C

Catalyst

Full Member level 3
Joined
Jan 22, 2005
Messages
167
Helped
2
Reputation
4
Reaction score
2
Trophy points
1,298
Activity points
1,651
Inductance

Hi folks

I know this is really stupid to ask but......I always thought Inductance was a constant (i.e. doesn't change at different frequencies)

When i connect a 0.22uH inductor to an impedance analyser......Its inductance varies from 0.22uH to about 0.15uH (in the freq range 1MHz to 13MHz).

Why is it changing? surely it should be the same value independant of the frequency.



Thanks

Cat
 

Inductance

there is nothing ideal in life, inductors have parasitic capacitances and parasitic resistance . this may be the problem as when frequency change the parasitc caps effect may appear , i am not sure but this may be the case.
regards,
a.safwat
 

Re: Inductance

So really, this must be the same for capacitors.

If I want to make a resonant circuit say at 10MHz..........I should be measuring the L of the inductor at 10MHz ?

This also applies to any capacitors i may require (measure the capacitance at 10MHz)?


Is this correct?


Regards

Cat
 

Inductance

It is because of nonlinearity of inductor core.
This ninlinearity, change inductor value, when it's current or volatge magnitude changed.
I think if you use inductor without core (winding on air) it's inductance will be fixed.

Regards,
Davood.
 

Inductance

Well inductors are made of conductors that are solated. If you think two wounds like charge and betwen them an isolator you have a capacitor. So in your inductor you have a Inductor, for low frequencies, but if you increases the frequency of operation parasite capacitancies will appear and cancell part of the inductance called DIP. AT some point of frequency capcitances will be great than inductance and your inductor will operate like a capacitor.

If you have access to a Universal Bridge you can comprobe that situation and select an area where your inductor stay almost constant.

For your case you must verify that your inductor won't be at any DIP or nearby a DIP.
 

Re: Inductance

When you say DIP, do you just mean a steep dip in inductance or is DIP an abbreviation?



Cheers

Cat
 

Re: Inductance

Also, does this mean a capcitor can actually behave like an inductor at higher frequencies as well?
 

Inductance

In this case when you plot the XL vs frequency
DIP is a depresion in the XL (inductive reactance) when a little parasitic capacitance anules part of the inductance.
 

Re: Inductance

every inductor have a self resonance frequency because of the parasetic capacitors with it this self resonance change the value of inductor and after this freq the inductor behave as capacitor if u working bellow this freq u will see the inductance almost constant but near this freq u will find the inductance change greatly
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top