Swinging Choke or Smoothing Choke

danFrank · 10th February 2007, 07:52 PM

Hi Everybody,
I have a question. What is the difference in a swinging choke and a smoothing choke and what is their respective theories of opperation? Not looking for a scientific paper, just a simple explanation. Also, how are they different physically (are they assembled differently, different core, etc)?
I see a lot of equipment has one of each, first one is swinging and the last one is a smoothing choke in a LCL filter.
Thanks in advance...
Daniel

ray_moth · 10th February 2007, 08:48 PM

A smoothing choke has a 'normal' sized air-gap in its core, designed to maintain a fairly constant inductance up to the maximum direct current for which it is specified. It is intended for use in a capacitor-input filter, but it can also be used satisfactorily in a choke-input filter if there is no significant variation in current demand. A smoothing choke has to be built with a relatively large iron core, in order to obtain the required inductance despite its large air-gap (just like an OP transformer intended for SE operation).

A swinging choke is intended to be used as the first choke in a choke-input filter in cases where the current demand varies considerably, such as for feeding class AB or B amplifiers. It has a very small air-gap in the core, so that it will become more saturated and its inductance will fall as the current demand rises. This is done because the required inductance is less at higher current. Its inductance should be (but often isn't) specified as a range (e.g. 1Hy to 5Hy) over the current range for which it is intended to be used. A swinging choke, having a smaller air-gap, needs a relatively small iron core, so it is lighter and less bulky than a smoothing choke of similar inductance.

danFrank · 10th February 2007, 09:23 PM

Thanks for the reply.
Daniel

Tweeker · 11th February 2007, 10:29 AM

Swinging chokes achieve better regulation for class AB and B stages, but cannot be resonated well and have lower inductances at high currents. In a class A amp a smoothing choke is the better choice.

Tweeker · 11th February 2007, 11:05 AM

Its also hard to find new swinging chokes. Peter Dahl is the only US source I can think of offhand.

10th February 2007, 07:52 PM	#1
danFrank diyAudio Member Join Date: May 2005 Location: California	Swinging Choke or Smoothing Choke Hi Everybody, I have a question. What is the difference in a swinging choke and a smoothing choke and what is their respective theories of opperation? Not looking for a scientific paper, just a simple explanation. Also, how are they different physically (are they assembled differently, different core, etc)? I see a lot of equipment has one of each, first one is swinging and the last one is a smoothing choke in a LCL filter. Thanks in advance... Daniel

11th February 2007, 10:29 AM	#4
Tweeker diyAudio Member Join Date: Dec 2004 Location: Cincinnati, Ohio	Swinging chokes achieve better regulation for class AB and B stages, but cannot be resonated well and have lower inductances at high currents. In a class A amp a smoothing choke is the better choice. __________________ Be sure your foil hat has a good low impedance ground.

11th February 2007, 11:05 AM	#5
Tweeker diyAudio Member Join Date: Dec 2004 Location: Cincinnati, Ohio	Its also hard to find new swinging chokes. Peter Dahl is the only US source I can think of offhand. __________________ Be sure your foil hat has a good low impedance ground.

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10th February 2007, 08:48 PM	#2
ray_moth diyAudio Moderator Emeritus Join Date: Jan 2004 Location: Jakarta	A smoothing choke has a 'normal' sized air-gap in its core, designed to maintain a fairly constant inductance up to the maximum direct current for which it is specified. It is intended for use in a capacitor-input filter, but it can also be used satisfactorily in a choke-input filter if there is no significant variation in current demand. A smoothing choke has to be built with a relatively large iron core, in order to obtain the required inductance despite its large air-gap (just like an OP transformer intended for SE operation). A swinging choke is intended to be used as the first choke in a choke-input filter in cases where the current demand varies considerably, such as for feeding class AB or B amplifiers. It has a very small air-gap in the core, so that it will become more saturated and its inductance will fall as the current demand rises. This is done because the required inductance is less at higher current. Its inductance should be (but often isn't) specified as a range (e.g. 1Hy to 5Hy) over the current range for which it is intended to be used. A swinging choke, having a smaller air-gap, needs a relatively small iron core, so it is lighter and less bulky than a smoothing choke of similar inductance.

10th February 2007, 09:23 PM	#3
danFrank diyAudio Member Join Date: May 2005 Location: California	Thanks for the reply. Daniel

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