Inverter resistance welding control apparatus
First Claim
1. An inverter resistance welding control apparatus for use in resistance welding effected by the supply of a welding current to a material to be welded, which is electrically connected to a secondary coil of a welding transformer, said resistance welding control apparatus comprising:
- a rectifying circuit for converting an alternating current at a commercial frequency into a direct current;
an inverter including two pairs of uni-directional conduction switching elements, each pair of switching elements having an input terminal electrically connected to an output terminal of said rectifying circuit and having an output terminal electrically connected to a primary coil of said welding transformer;
a diode connected, in parallel to each switching element of said inverter, with its polarity of conduction reversed to that of said switching element;
current supply sequential control means for switchingly selecting, in a predefined sequence, a first current supply mode in which a welding power from said rectifying circuit is fed to said welding transformer by way of first and second switching elements constituting a first pair in said inverter, and a second current supply mode in which a welding power from said rectifying circuit is fed to said welding transformer by way of third and fourth switching elements constituting a second pair in said inverter; and
switching control means which in said first current supply mode, iteratively turns ON/OFF, at a predetermined inverter frequency, only one of said first and second switching elements while keeping the other ON and which in said second current supply mode, iteratively turns ON/OFF, at said inverter frequency, only one of said third and fourth switching elements while keeping the other ON.
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Accused Products
Abstract
When a second switching element Q2 is changed over from ON state to OFF state for each switching cycle while a first switching element Q1 remains ON in a unit weld period Ta for example, a primary current I1 does not come to a stop at once under the influence of inductance of a welding transformer 16 but it flows as a transient current i through a primary circuit until it is off. The transient current i makes a closed circuit through which it flows from a primary coil of the welding transformer 16 via a third diode D3 and then a first switching element Q1 again into the primary coil of the welding transformer 16. More specifically, due to the first switching element Q1 being kept ON, the transient current i which has passed through the third diode D3 flows through the first switching element Q1, without passing through a capacitor 12, and comes back into the primary coil of the welding transformer. Little or substantially no current flows through the capacitor 12.
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Citations
5 Claims
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1. An inverter resistance welding control apparatus for use in resistance welding effected by the supply of a welding current to a material to be welded, which is electrically connected to a secondary coil of a welding transformer, said resistance welding control apparatus comprising:
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a rectifying circuit for converting an alternating current at a commercial frequency into a direct current; an inverter including two pairs of uni-directional conduction switching elements, each pair of switching elements having an input terminal electrically connected to an output terminal of said rectifying circuit and having an output terminal electrically connected to a primary coil of said welding transformer; a diode connected, in parallel to each switching element of said inverter, with its polarity of conduction reversed to that of said switching element; current supply sequential control means for switchingly selecting, in a predefined sequence, a first current supply mode in which a welding power from said rectifying circuit is fed to said welding transformer by way of first and second switching elements constituting a first pair in said inverter, and a second current supply mode in which a welding power from said rectifying circuit is fed to said welding transformer by way of third and fourth switching elements constituting a second pair in said inverter; and switching control means which in said first current supply mode, iteratively turns ON/OFF, at a predetermined inverter frequency, only one of said first and second switching elements while keeping the other ON and which in said second current supply mode, iteratively turns ON/OFF, at said inverter frequency, only one of said third and fourth switching elements while keeping the other ON. - View Dependent Claims (2, 3, 4, 5)
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Specification