Progressive power monitor for a current controlled resistance welder
First Claim
1. A progressive power limit control system for use with a resistance welder having a weld transformer for supplying weld current to at least one pair of contact tips, said system comprising:
- A. a microprocessor;
B. a stepper program operating in said microprocessor, said program for increasing said weld current in increments following a stepper current profile having a plurality of weld cycles;
C. a current sensor for sensing said weld current, said current sensor for providing weld current data;
D. a voltage sensor for sensing voltage supplied to said weld transformer, said voltage sensor for providing voltage data;
E. means for calculating weld power from said current data and said voltage data at each of said plurality of weld cycles;
F. means for comparing said calculated weld power with a characteristic power profile at each of said plurality of weld cycles, said characteristic power profile having an upper power threshold and a lower power threshold;
G. means for indicating an event condition of said resistance welder if said calculated weld power exceeds said upper power threshold or is below said lower power threshold; and
H. means for establishing said characteristic power profile at each of said plurality of weld cycles over a range of weld currents specified by said stepper program.
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Accused Products
Abstract
A weld controller utilizing a constant current control employs a stepper program for increasing current boost in predetermined percentage increments or steps following a predetermined stepper current profile to provide compensation for contact tip wear. The weld controller acquires weld power data in the form of current and voltage samples for each step of the stepper program, and computes Volt Amperes or power from this data during an acquisition run through the stepper program. The stepper program specifies a constant current at each step. Associated with each incremental current step, weld power that is required to produce that weld current is determined by the weld controller to generate a characteristic power curve. The power curve will be over the range of currents as specified by the combination of the programmed weld current and the range of current boost as specified by the stepper schedule. The weld controller will build a table of values relating weld current and delivered power or Volt Amperes. Once this table is complete, the table is available for an operator to edit, view, or copy into a characteristic power curve file for the weld system. Subsequent operations of the weld controller will utilize high and low power limit thresholds that track the nominal power profile. An event condition will be declared if the weld power is outside the lower or upper threshold. The thresholds can be defined as a fixed offset from the profile or as a percentage of the profile at each step of the stepper program. This allows the use of power limits to be established in close proximity to the nominal weld power at all times, enabling the use of tighter tolerances.
30 Citations
23 Claims
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1. A progressive power limit control system for use with a resistance welder having a weld transformer for supplying weld current to at least one pair of contact tips, said system comprising:
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A. a microprocessor; B. a stepper program operating in said microprocessor, said program for increasing said weld current in increments following a stepper current profile having a plurality of weld cycles; C. a current sensor for sensing said weld current, said current sensor for providing weld current data; D. a voltage sensor for sensing voltage supplied to said weld transformer, said voltage sensor for providing voltage data; E. means for calculating weld power from said current data and said voltage data at each of said plurality of weld cycles; F. means for comparing said calculated weld power with a characteristic power profile at each of said plurality of weld cycles, said characteristic power profile having an upper power threshold and a lower power threshold; G. means for indicating an event condition of said resistance welder if said calculated weld power exceeds said upper power threshold or is below said lower power threshold; and H. means for establishing said characteristic power profile at each of said plurality of weld cycles over a range of weld currents specified by said stepper program. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A weld controller having a progressive power limit control system for use with a resistance welder having a weld transformer for supplying weld current to at least one pair of contact tips to create heat between at least two workpieces, said weld controller having a plurality of welding cycles, said weld controller system comprising:
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A. a microprocessor; B. welder power means controlled by a program operating in said microprocessor and operatively connected to said weld transformer for supplying weld current to said contact tips to create said heat in said workpieces, said program for increasing said weld current in increments following a predetermined current profile having a plurality of weld cycles to provide compensation for deterioration of said contact tips wear; C. a current sensor for sensing current supplied by said welder power means to said weld transformer, said current sensor for providing weld current data; D. a voltage sensor for sensing voltage supplied to said weld transformer, said voltage sensor for providing voltage data; E. means for calculating weld power from said current data and said voltage data at each of said plurality of weld cycles; F. means for comparing said calculated weld power with a characteristic power profile at each of said plurality of weld cycles, said characteristic power profile having an upper power threshold and a lower power threshold; G. means for indicating an event condition if said calculated weld power exceeds said upper power threshold or is below said lower power threshold; and H. means for establishing said characteristic power profile at each of said plurality of weld cycles over a range of weld currents specified by said stepper program. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification