Welding system controller

Claim 2

Alternating-current welding apparatus comprising: a welding transformer of the type having a generally square hysteresis loop and with its primary winding energized by an alternating-current source, a primary circuit for said transformer including at least two oppositely poled silicon controlled rectifiers each selectively controlling the application of current to the primary winding on a respective half-cycle of transformer primary current of a particular polarity, and control means for selectively rendering one of said silicon controlled rectifiers conductive, said control means including a memory means distinctively operated concurrently with the enaBling of said one silicon controlled rectifier permitting a current pulse of one polarity through said transformer primary winding, said memory means being effective to ensure that only the other said silicon controlled rectifier can be enabled on the next half cycle of current in said transformer primary winding so as to ensure that successive current pulses through said transformer winding are of opposite polarity thereby avoiding saturation of the transformer.

Claim 3

The apparatus of claim 1 which further comprises means for sensing the voltage on said primary and producing a signal when the voltage passes through zero, delay means included within said control means, coupled to said last named means to provide an output a pre-selected time after the occurrence of said signal, said output coupled to and operating said memory means and enabling one or the other of said silicon control rectifiers as determined by said memory means.

Claim 4

The apparatus of claim 2 which further comprises means effective only on the first half-cycle of current flow in said primary to increase said pre-selected time by a variable time related to said pre-selected time so as to minimize the transition between not welding and welding.

Claim 5

The apparatus of claim 3 which further comprises means effective only after the last welding half-cycle, to increase said pre-selected time by a variable time related to said pre-selected time so as to minimize the transition from welding and not welding.

Claim 6

Alternating-current welding apparatus comprising: a welding transformer of the type having a generally square hysteresis loop and with its primary winding energized by an alternating-current source, said primary winding circuit for said transformer including switching means for controlling the flow of alternating current through said primary winding during a variably controllable portion of each of successive half-cycles of the alternating current source, heat intensity control means coupled to comparator means, said heat intensity control means providing a control signal of preselected amplitude which is linearly related to a preselected heat intensity demand, means, also coupled to said comparator means, generating on each successive sine wave loop constituting a half-cycle of the transformer primary voltage a reference signal having a waveform corresponding to the integral of the sine wave loop, said comparator means effective on each of successive half-cycles of the transformer primary voltage as said reference signal rises in amplitude to exceed said control signal to control said switching means permitting a flow of current through said primary winding, whereby the power delivered to said transformer secondary is linearly related to the preselected heat intensity demand.

Claim 7

Alternating-current welding apparatus comprising: a welding transformer of the type having a generally square hysteresis loop and with its primary winding energized by an alternating-current source, said primary winding circuit for said transformer including switching means for controlling the flow of alternating current through said primary winding during a variably controllable portion of each of successive half-cycles of the alternating current source, heat intensity control means coupled to comparator means, said heat intensity control means providing a control signal of preselected amplitude which is linearly related to a preselected heat intensity demand, means, also coupled to said comparator means, generating on each successive sine wave loop constituting a half-cycle of the transformer primary voltage a reference signal having a waveform corresponding to the integral of the sine wave loop, said comparator means effective on each of successive half-cycles of the transformer primary voltage as said reference signal rises in amplitude to exceed said control signal to control said switching means permitting a flow of current through said primary winding, whereby the power delivered to said transformer secondary is linearly related to the preselected heat intensity demand.

Claim 8

The apparatus of claim 5 wherein said comparator produces a train of signals to control said switching means, said switching means comprises a pair of oppositely poled silicon control rectifiers each connected across said primary, a bistable circuit coupled to said comparator for dividing the train of singals from said comparator into two alternate trains, said bistable circuit means providing signals to control said silicon control rectifiers, each of said alternate trains of signals respectively controlling one of said silicon control rectifiers.

Claim 9

A welding control circuit comprising, switch means providing, at selected times a welding signal, a welding transformer with primary and secondary windings, said primary winding being selectively excited by alternating current, zero detecting means coupled to said primary winding to produce a repetitive signal once each time the voltage across said primary winding goes through zero, a delay circuit coupled to said zero detecting means for delaying each of said repetitive signals by a variable predetermined amount, a bistable circuit means coupled tO said delay circuit producing alternate signals related to said repetitive signals, and means, connected to said switch means, said bistable circuit means, and said primary winding to only allow current to flow in said primary winding in alternate directions successively.

Claim 10

A welding control circuit comprising, switch means providing, at selected times a welding signal, a welding transformer with primary and secondary windings, said primary winding being selectively excited by alternating current, zero detecting means coupled to said primary winding to produce a repetitive signal once each time the voltage across said primary winding goes through zero, a delay circuit coupled to said zero detecting means for delaying each of said repetitive signals by a variable predetermined amount, a bistable circuit means coupled tO said delay circuit producing alternate signals related to said repetitive signals, and means, connected to said switch means, said bistable circuit means, and said primary winding to only allow current to flow in said primary winding in alternate directions successively.

Claim 11

The circuit of claim 7 wherein said delay circuit further comprises, a linear circuit having an input and an output and producing an output which is linearly related to its input and calibrated in percent heat values, a comparison circuit having two inputs and an output, said linear circuit output coupled to one said input of said comparison circuit, integration means having an input and output and producing an output which is the integral of its input, means connecting said integration means input to said primary, said integration means being connected to said zero detecting means and responsive thereto to operate, said output of said integration means connected to the other input of said comparison circuit, said comparison circuit producing said repetitive signals whenever said integration means output exceeds said linear circuit output, whereby said repetitive signals allow current to flow in said primary producing a heat output which is determined by the relationship between the input and output of said linear circuit.

Claim 12

The circuit of claim 8 which further comprises, a second delay circuit including resistance means and capacitance means, said linear circuit output connected to said comparison circuit through said second delay circuit, second switch means connected across said resistance means, means connected to said bistable circuit means and said second switch means for closing said second switch after each of said alternate signals produced by said bistable circuit means.

Claim 13

In the circuit of claim 9, further comprising, means associated with said switch means for producing an end-of-weld signal, third switch means, said linear circuit output being connected to said second delay circuit through said third switch means, said third switch means being connected to said switch means and said associated means to close in response to said weld signal and open in response to said end-of-weld signal, means connecting said linear circuit input to said second delay means through further resistance means, fourth switch means connected across said further resistance means, and means responsive to said end-of-weld signal from said associated means for closing said fourth switch means for a predetermined time.

Claim 14

The circuit of claim 7 which further comprises fault detecting means coupled to said primary winding including current fault detecting means to detect the absence of welding current flow.

Claim 15

The circuit of claim 11 which further comprises switch fault detecting means to detect the absence of a voltage applied to said last named detecting means.