Abstract: A monitoring and control system for a resistance welding apparatus. The system monitors the quality of a weld as a weld is formed and terminates the welding current when a quality weld is completed. The monitoring function is performed by detecting a change in the instant welding current is extinguished at the end of half cycles of welding current in the secondary winding circuit of the welding transformer. The weld current is terminated when a detected charge in the instant current is extinguished relative to a reference equals a preprogrammed value which is indicative of an acceptable quality weld between welded parts.

Abstract: A control system for resistance welders of the type in which welding current is supplied to a workpiece through a transformer. The system assures weld quality by monitoring the change in resistance across the weld during the welding operation without the need for auxillary leads or separate sensing transducers at or near the workpiece and automatically terminates the welding current when a quality weld is made as determined by resistivity characteristics of the weld. The system monitors discrete changes in the characteristics of the current in the primary of the welding transformer which occur as a result of changes in weld resistance. The system compares the monitored current characteristics of the welding current with a plurality of parameters indicative of a quality weld and terminates the welding current when a selected number of monitored characteristics are within selected parameters.

Abstract: A control system for resistance welders of the type in which welding current is supplied to a workpiece through a transformer. The system assures weld quality by monitoring the change in resistance across the weld during the welding operation without the need for auxillary leads or separate sensing transducers at or near the workpiece and automatically terminates the welding current when a quality weld is made as determined by weld resistivity characteristics. The system monitors discrete changes in the characteristics of the current in the welding transformer which occur as a result of changes in weld resistance.

Abstract: A power factor monitoring and control system for controlling the quality of a spot weld made by assembly line welders. The control system of the present invention detects a change in the load power factor as the weld is formed which is manifested as a change in the current extinction angle of the half cycles of weld current. The time interval between the instant weld current is extinguished at the end of a programmed half cycle and an instant when current is extinguished at the end of a subsequent half cycle provides a measure of the resistance across the weld nugget. The time interval information is stored and compared with information provided during a previous half cycle to generate a difference signal. The change in resistance in the secondary circuit is reflected through the transformer to the transformer primary circuit as a decrease in power factor.

Abstract: A power factor monitoring and control system with line disturbance immunity for controlling the quality of spot welds made by resistance welding techniques such as those used in the automotive industry on assembly line welders. As is commonly known, quality and strength of a spot weld can be correlated to a change in resistance measured through the weld as the weld progresses during the fusion progress. This change in resistance in the secondary circuit reflects back through the transformer to its primary circuit as a change in power factor. The timing changes resulting from the change in power factor are sensed by the control circuitry of this system to generate signals which are used by an 8-bit microprocessor properly programmed to operate on the signal information. By determining the amount of increase or decrease that has occurred in the current conduction angle during a group of welds, a basis for the control of the welding heat is obtained.

Abstract: An automatic voltage compensation control for a microprocessor controlled resistance welder system includes a digital voltmeter for measuring the line voltage cycle by cycle and associated circuitry to compensate the welding current in response to the measured line voltage in a manner which tends to hold the welding current constant and independent of line voltage variations. The digital voltmeter consists of a voltage-to-frequency converter coupled to a counter. The output of the voltage-to-frequency converter which is proportional to the line voltage is accumulated for the period of one cycle of the line frequency. This produces in the counter at the end of each measurement interval, a number of counts proportional to the average line voltage. The microprocessor using the count obtained adjusts the welding current by altering the timing of the firing points of the SCR contactors used to control the welding current.

Abstract: A method to control the welding transformer residual magnetizing current which normally continues circulating in the secondary circuit at the end of each welding pulse until the tips are opened. By utilizing a firing delay of the last half cycle in each welding pulse that brings the algebraic sum of the volt-seconds applied to the transformer to zero at the end of each welding pulse, the residual secondary current is nulled. This alleviates magnetizing current problems which occur in multiple pulse welding.

Abstract: A Power Factor Monitoring and Control System for controlling the quality of a spot weld made in the automotive industry on assembly line welders. The quality and strength of a spot weld can be correlated to a drop in resistance during the fusion process. Rather than measuring this resistive drop at the welding electrodes by attaching external sensing means thereto, the control system of the present invention makes use of the phenomenon that a resistive drop also causes a change in the total load power factor further resulting in a change to the current extinction angle of a weld half cycle. By determining the amount of increase or decrease that has occurred in the current extinction angle during a weld or a group of welds, a basis for the control of the welding heat is obtained.

Abstract: In an electric motor having an external motor cooling fan mounted outboard of one of its rotor shaft bearings, the cup-shaped enclosure for said fan conventionally has its side wall radially spaced from a part of the frame to cooperate therewith in defining an annular outlet through which air from said fan is guided axially across the motor exterior, all around the same. According to the invention, that outlet is substantially blocked, as by an arcuate air barrier strip, to convert the fan enclosure into a plenum chamber from which pressurized air is forced through the motor interior for substantially greater cooling effectiveness.