Abstract: This invention relates to methods to control the resistance spotwelding process using an electric servomotor actuator to move the welding electrodes to the work and apply force to them. Measurements of actuator position, servomotor drive voltage, servomotor drive current, voltage across the welding electrodes, welding transformer primary current, welding transformer secondary current and power factor in the primary circuit of the welding transformer are used separately and in combination to determine various conditions such as identify defects in the welding machine, the electric cabling, the welding process and in the weld itself. Depending upon the defect found, the welding parameters are changed to overcome the defect, and/or the need for an additional weld is indicated and/or an error indication is generated.

Abstract: This invention relates to methods to control the resistance spotwelding process using an electric servomotor actuator to move the welding electrodes to the work and apply force to them. Measurements of actuator position, servomotor drive voltage, servomotor drive current, voltage across the welding electrodes, welding transformer primary current, welding transformer secondary current and power factor in the primary circuit of the welding transformer are used separately and in combination to determine various conditions such as identify defects in the welding machine, the electric cabling, the welding process and in the weld itself. Depending upon the defect found, the welding parameters are changed to overcome the defect, and/or the need for an additional weld is indicated and/or an error indication is generated.

Abstract: A signal integrator stabilization circuit comprises an operational amplifier functioning as a comparator. The circuit further comprises an attenuator in the amplifier's feedback, thereby generating a feedback signal which is sampled to produce a sampling signal. The integrator is driven with a preselected ratio of the feedback signal and the sampling signal to produce a stabilized output signal approaching a zero value which has a good DC stability without compromising the ability to accurately integrate high frequency signals.

Abstract: A method and system for controlling the output current of large, low-voltage, DC power supply which includes at least one transformer primary by controllably switching an AC power line voltage to the primary as a function of actual and desired output currents. SCRs are used to switch, using phase control, the AC primary voltage to the transformer(s) of the power supply in order to control the output current. Given the incoming power line voltage, the current value from the previous power line cycle and the desired current for the present cycle, the function is used to find the SCR firing angle to attain the desired output current in the present power line cycle. Actual measurements of output current and power line voltage are used to modify the function to reflect changes in power line voltage and/or circuit impedance to obtain a modified function.

Abstract: A method is disclosed for controlling the magnitude of current delivered through welding electrodes to a workpiece to be welded using resistance welding techniques, in order to prevent weld expulsion and concomitant diminishment of weld quality. Weld expulsion is detected by determining changes in resistance during formation of the weld, by periodically determining the power factor, and the primary circuit of the welding transformer. The power factor is determined by determining the relative timing between the commencement of the applied voltage, the zero crossover point of the applied voltage, and the ensuing zero point of the applied current.

Abstract: Structure for and method of controlling the firing point of thyristors in a phase controlled contactor in a resistance welding circuit in accordance with variations in current line voltage and/or one of resistance and inductive impedance in the welding circuit including structure for and the method of determining the firing point in a cycle of alternating electrical energy fed to the welder in terms of its distance from zero voltage cross over point and determining the current lag after a subsequent zero voltage cross over point of the voltage signal, determining the power factor of the welding circuit from these angular measurements and selecting a new firing delay for the contactor in accordance with the circuit power factor and the percent heat selected in the welding circuit, and subsequently correcting the firing delay in accordance with the percent heat selected in view of changes in the line voltage and circuit current.

Abstract: High frequency resistance spot welding structure and method. In one embodiment, the structure includes dual, mirror image welding transformers, each including a transformer secondary circuit, an endless transformer core, and a transformer primary winding wound around the transformer core. The transformer secondary circuits may be single member, U-shaped transformer secondaries with integral electrode portions. In another embodiment, one of the transformers is replaced by a pair of spaced apart welding electrodes which are connected by a conductor. Means are provided for supplying welding pressure to the transformers to move them with their associated welding electrodes during a weld sequence. A high frequency, electrical welding signal is applied to the transformer primary circuits which are synchronized when two transformers are used so that the welding currents passing through the transformer secondary circuits reinforce each other.

Abstract: Structure for and a method of resistance welding using an induction coupled power source. The structure of the invention comprises an electric coil wrapped around a flux concentrating core in close proximity to members to be welded together, a source of alternating electrical energy connected through the coil and means for applying pressure between the members to be welded. In accordance with the method of the invention the members to be welded are heated by at least one of an induced current and hysteresis loss and the heated members are then forged together by applying pressure thereon. The weld effected by the method of the invention may be either a spot weld or a continuous weld. Further in accordance with the structure of the invention the flux concentrating core may be on one or both sides of the materials to be welded and may be linear and perpendicular or at an angle to the members to be welded, or may be U-shaped or cup-shaped including a central post around which the coil is wrapped.

Abstract: A method of and structure for high speed seam welding. The method comprises placing an auxiliary transformer between a three phase source of electrical welding energy and seam welder structure, which auxiliary transformer includes three separate primary windings connected to the separate phases of the source of welding energy, phase controlling the energizing of each separate primary winding and energizing the seam welder from the auxiliary transformer. In one embodiment, the phases of the auxiliary transformer are energized in the order of the phase of the welding energy and a delay of approximately 120.degree. of the welding energy is provided between the energizing of each auxiliary transformer winding. In another embodiment of the invention, the auxiliary transformer primary windings are energized in a first, third, second, welding energy phase order with a delay of 240.degree.

Abstract: Structure for and method of eliminating impedance in multiphase direct current power supplies comprising connecting transformer primary windings in Y configuration with contactor structure, whereby multiple impedance paths through transformer secondary circuits are provided.

Abstract: A monitoring and control system for use in conjunction with a pulsation type welder which utilizes a computer to calculate the impedance characteristics of a weld and compare these characteristics to a preselected set of characteristics to determine if a quality weld has been made. The system then controls the heat and cool time to increase or decrease the temperature of the weld and thus control the size of the weld nugget. The monitoring control system is utilized in conjunction with a standard pulsation welding control system, which standard system provides a series of heat impulses each followed by a cool interval, this cycle being repeated for a preselected number of cycles. The monitoring and control system senses the voltage and current in the welding load and feeds this data to a computer which, in turn, calculates the impedance of the weld.