Browse Prior Art Database

Improved Common Mode Choke

IP.com Disclosure Number: IPCOM000035113D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Buhler, OR: AUTHOR

Abstract

Described is an improved winding of a toroidal common mode choke for AC line filters that permits increased current flow before saturation occurs.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 83% of the total text.

Page 1 of 2

Improved Common Mode Choke

Described is an improved winding of a toroidal common mode choke for AC line filters that permits increased current flow before saturation occurs.

Fig. 1 illustrates the usual common mode choke windings on a toroidal core. Large differential current can flow without causing saturation because the flux produced by each winding opposes the flux produced by the other winding. Common mode noise current produces a net flux vector that opposes noise current flow.

For nonlinear loads, e.g., fusers and lamps in electrophotographic printers and copiers, surge currents a magnitude greater than the steady state currents can saturate even common mode chokes, permitting noise to pass through on the AC power lines.

Not all the flux produced by the windings is contained within the toroidal core. Some surrounds the windings outside the core. The outside flux causes leakage inductance which can saturate the core.

As shown in Fig. 2, winding the coils in two parts reduces the distance between opposing coils which, in turn, reduces leakage.

The number of parts the windings can be divided into can be increased. The limit is an alternately wound coil. Before the limit is reached, however, the extra insulation required produces diminishing returns.

The use of split winding can be extended to three-phase power. Fig. 3 shows a three winding delta choke. The use of split windings in three-phase power has an additional advantage of better separation of input fro...