Stange looking wound choke arrangement?

Status
Not open for further replies.
P

PhaseShift

Senior Member
Was looking in a control cabinet today and output of a VFD had the ouput leads wrapped several times around what looked like to be a CT. This was not a CT nor did it have any secondary leads, but it did have some kind of circular plastic housing which inside had some sort of metal core.

What is the purpose of wrapping several leads around this device? Is this some kind of ouput choke? How does it work?
 
PhaseShift said:
Was looking in a control cabinet today and output of a VFD had the ouput leads wrapped several times around what looked like to be a CT. This was not a CT nor did it have any secondary leads, but it did have some kind of circular plastic housing which inside had some sort of metal core.

What is the purpose of wrapping several leads around this device? Is this some kind of ouput choke? How does it work?
Click to expand...
They are called 'ferrite cores'. Yes they are chokes. Effectively, they are 'field' wound iron core inductors.
 
Sounds like a hand made output reactor. People do this more often that one might think. Here is an extreme version I ran across in a how-to forum for machinists.

LineReactorQE.jpg


It works, as long as you are not looking for much inductance out of it and safety is of little concern.
 
A little history:

A little history:

The ferrite core is mainly powdered iron held together with some sort of binder and pressed into a doughnut shape. In ancient times computer memories were made with arrays of tiny ferrite cores interlaced with word lines, bit lines, and sense lines. Core memory has long ago been supplanted with electronic memory.
 
John120/240 said:
What is the purpose of a contrapion such as this?
Click to expand...
Simply, they minimize high-frequency signals (noise) generated in electronics and picked up on cables from entering or leaving equipment. That's what's in the cylindrical lumps on one or both ends of most computer cables.

They act as low-pass filters, and provide a high impedance to these signals similarly to the way a GEC in a metallic raceway that is not bonded to it at both ends can to lightning-induced currents.
 
PhaseShift said:
Was looking in a control cabinet today and output of a VFD had the ouput leads wrapped several times around what looked like to be a CT. This was not a CT nor did it have any secondary leads, but it did have some kind of circular plastic housing which inside had some sort of metal core.

What is the purpose of wrapping several leads around this device? Is this some kind of ouput choke? How does it work?
Click to expand...

VFDs often have input and output chokes to minimize harmonics going back to the supply (input) and going to the motor (output)
 
Status
Not open for further replies.
Top