Electromagnetic contactor

An electromagnetic contactor, comprising:

• a pair of fixed contacts disposed to maintain a predetermined interval;
• a movable contact disposed to be capable of contacting with and separating from the pair of fixed contacts;
• and
• an electromagnetic unit driving the movable contact,
• wherein the electromagnetic unit includes:
• a magnetic yoke with a U-shaped cross section, having an open upper part;
• an upper magnetic yoke cross-linked in the open upper part of the magnetic yoke with the U-shaped cross section;
• a spool disposed on a bottom plate part of the magnetic yoke with the U-shaped cross section, and having an exciting coil wound therearound and a central opening;
• a movable plunger movably disposed in the central opening of the spool in an axial direction and having a tip end protruding through an opening formed in the upper magnetic yoke, the movable plunger being urged by a return spring;
• and
• a tubular auxiliary yoke forming a magnetic path between the movable plunger and the magnetic yoke with the U-shaped cross section when the movable plunger is in an open position,
• wherein the movable plunger is coupled to the movable contact through a coupling shaft,
• the magnetic yoke with the U-shaped cross section comprises a bottomed tubular body having an open upper end,
• the tubular auxiliary yoke comprises:
• an annular plate part fixed to a bottom plate part of the bottomed tubular body and having a central opening, and
• a tubular part formed integrally with an inner circumferential surface of the annular plate part, extending upward, and proximally facing an outer circumferential surface of the lower end part of the movable plunger.

An electromagnetic contactor, comprising:

• a pair of fixed contacts disposed to maintain a predetermined interval;
• a movable contact disposed to be capable of contacting with and separating from the pair of fixed contacts;
• and
• an electromagnetic unit driving the movable contact,
• wherein the electromagnetic unit includes:
• a magnetic yoke with a U-shaped cross section, having an open upper part;
• an upper magnetic yoke cross-linked in the open upper part of the magnetic yoke with the U-shaped cross section;
• a spool disposed on a bottom plate part of the magnetic yoke with the U-shaped cross section, and having an exciting coil wound therearound and a central opening;
• a movable plunger movably disposed in the central opening of the spool in an axial direction and having a tip end protruding through an opening formed in the upper magnetic yoke, the movable plunger being urged by a return spring;
• and
• a tubular auxiliary yoke forming a magnetic path between the movable plunger and the magnetic yoke with the U-shaped cross section when the movable plunger is in an open position,
• wherein the movable plunger is coupled to the movable contact through a coupling shaft,
• g1<g2 and g3<g4 are established in an open state of the movable plunger, and g1<g2 and g3>g4 are established in a closed state of the movable plunger,
• the g1 represents a gap between a peripheral flange part of the movable plunger and the upper magnetic yoke,
• the g2 is a gap between an outer circumferential surface of the movable plunger and an inner circumferential surface of an opening of the upper magnetic yoke,
• the g3 is a gap between the movable plunger and the tubular auxiliary yoke, and
• the g4 is a gap between the bottom surface of the movable plunger and the bottom plate part of the magnetic yoke with the U-shaped cross section.