Monitoring circuits for electrical welding apparatus
First Claim
1. A monitoring circuit for monitoring the electrical energy expended in forming a weld nugget during one half-cycle of an a.c. resistance welding apparatus, which comprises first means for deriving a voltage in quadrature phase relation to the resistive component in-phase with the welding current, second means for deriving a monitored weld voltage which inherently contains a significant reactive component due to electromagnetic effects, and summing means for summing the quadrature voltage and the monitored weld voltage in such manner that the reactive component of the monitored weld voltage is substantially cancelled by the quadrature voltage, and for producing a voltage output signal representative of their sum, said output signal being thereby representative substantially only of the resistive or in-phase component of the weld voltage.
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Accused Products
Abstract
A monitoring circuit for an a.c. resistance welding apparatus for can bodies is arranged to produce an output signal which is representative of the integral with respect to time of the resistive or in-phase component of the welding voltage taken over the half-cycles of welding current. The output signal is representative of the energy expended during welding, and may be used for indication or control.
10 Citations
15 Claims
- 1. A monitoring circuit for monitoring the electrical energy expended in forming a weld nugget during one half-cycle of an a.c. resistance welding apparatus, which comprises first means for deriving a voltage in quadrature phase relation to the resistive component in-phase with the welding current, second means for deriving a monitored weld voltage which inherently contains a significant reactive component due to electromagnetic effects, and summing means for summing the quadrature voltage and the monitored weld voltage in such manner that the reactive component of the monitored weld voltage is substantially cancelled by the quadrature voltage, and for producing a voltage output signal representative of their sum, said output signal being thereby representative substantially only of the resistive or in-phase component of the weld voltage.
- 11. A monitoring circuit for monitoring the electrical energy expended in forming a weld nugget during one half-cycle of an a.c. resistance welding apparatus, comprising conductor means, adapted to be connected to welding electrodes engaging work to be welded, for providing a monitored weld voltage signal which is out-of-phase with the welding current because of distributed circuit inductance between the points being monitored and of voltage electromagnetically induced in the conductor means, and means for integrating said monitored weld voltage signal over said one half-cycle to produce an output signal representative of the integral of that component of the monitored weld voltage signal which is in-phase with the welding current over said half-cycle.
- 14. An a.c. resistance welding apparatus for the longitudinal seams of tubular bodies for cans, which includes first and second electrodes for contacting opposed parts of a said tubular body to be welded together, supply connections connected to the electrodes for supplying the same with a.c. electrical current, a monitoring circuit for monitoring the weld voltage across said electrodes and for producing an output signal representative of the electrical energy expended during each half-cycle of the welding current, said monitoring circuit being effective to produce, as said output signal, a signal representative of the integral with respect to time of substantially only the resistive or in-phase component of the weld voltage.
Specification