when we measure two inductor has the same number of turnfor example if the inductor is250 mh so the equivalent of connecting 2 inductor in parallel will be also 250 mh but if connected in parallel but out of phase it will measure like short circuits ( a few micro henry) my question is when we connect on inductor 20 turn(160 mh) in phase (in parallel) with one 25 turn(250 mh) what is the equivalent inductance in this case and what the equivalent inductance if they connected out of phase in parallel
thanks

 

Inductances sum in the same way you sum resistances.

The phase of the inductors have no effect assuming that they are independent (i.e. the flux from one does not interfere with the other).

 

when we measure two inductor has the same number of turnfor example if the inductor is250 mh so the equivalent of connecting 2 inductor in parallel will be also 250 mh but if connected in parallel but out of phase it will measure like short circuits ( a few micro henry) my question is when we connect on inductor 20 turn(160 mh) in phase (in parallel) with one 25 turn(250 mh) what is the equivalent inductance in this case and what the equivalent inductance if they connected out of phase in parallel
thanks

The only way two inductors of 250 mH connected in parallel can give a resultant inductance of 250 mH is if the two coils are wound on the same core. Is that the case for your problem?

If this is the case, why didn't you say so? It makes a great deal of difference.

 

the only way two inductors of 250 mh connected in parallel can give a resultant inductance of 250 mh is if the two coils are wound on the same core. Is that the case for your problem?

If this is the case, why didn't you say so? It makes a great deal of difference.

yes they wound on the same core

 

inductances sum in the same way you sum resistances.

The phase of the inductors have no effect assuming that they are independent (i.e. The flux from one does not interfere with the other).

the two inductors wound on the same core

 

Read this thread:

http://forum.allaboutcircuits.com/showthread.php?t=38072

especially post #5. You'll find the answer to your question there.

 

Read this thread:

http://forum.allaboutcircuits.com/showthread.php?t=38072

especially post #5. You'll find the answer to your question there.

please this formula for calculating inductance in both case (parallel inphase and out phase) so what is the inductance of(160mh(20turn) and 250mh(25turn)) connected parallel inphase and also for connecting parallel outphase and in both case they ara wounded on the same core

 

The formula is in the reference I gave you.

You must know the mutual inductance (M) between the two coils to calculate the effective inductance of the two coils in parallel. Do you know or can you measure M?

 

The formula is in the reference I gave you.

You must know the mutual inductance (M) between the two coils to calculate the effective inductance of the two coils in parallel. Do you know or can you measure M?

how can i measure mutual inductance in both case connected in parallel inpase and outphase
thanks

 

You would use a suitable instrument, for example, an LCR meter:

http://www.quadtech.com/lcr-meters.php

If you can't calculate M, but have to measure it, you might as well simply measure the inductance of the parallel combination of your two coils, and then you don't need to know M.