AWS J1.1M/J1.1 pdf free download

AWS J1.1M/J1.1 pdf free download.Resistance Welding Controls.
4 Control Nomenclature
4.1 Control Types
4.1.1 Single-Phase Alternating Current (AC)
Most modern single-phase AC resistance welding controls provide a voltage input to the resistance welding transformer determined by adjustment of the welding contactor conduction phase angle. Control function timing is based on AC line frequency and is usually determined in cycles. At a 60-Hz line frequency, the interval of each time increment (cycle) is 16.7 ms. At a 50-Hz line frequency, the interval of each time increment (cycle) is 20 ms. Control can be as fine as one half line cycle at heat settings from 10% to 99% of the available line voltage. These controls are used in conjunction with both AC and DC single-phase transformers.
4.1.2 Three-Phase I)irect Current (I)C)
A three-phase DC control incorporates two or three welding contactors to provide a controlled voltage input to a resistance welding transformer that consists of either three separate single-phase transformers (connected in wye or delta) or a single three-phase transformer equipped with a center-tapped rectifier on each phase.
4.1.3 Frequency Con’erter
Frequency converter controls, sometimes referred to as low frequency controls, convert three-phase power by means of supplying a group of positive half cycles (1 to 12 cycles) of a three-phase line and then alternately conducting an equal group of negative half cycles. If more heat is required, the control stops conducting for one cycle and then energizes all three phases for multiple cycles in the opposite direction. The result is a group of positive and negative voltage impulses used as either unfiltered DC or to imitate low-frequency AC. A frequency converter control operates the welding transformer at a frequency lower than line frequency; typically 4 Hz to 20 Hz. See Figure A. 10.
4.1.4 NIld-Frequency 1)irect Current (MFI)C)
MFDC controls rectify the 50/60 Hz power line input to generate an output of up to 10 kHz (commonly 800 Hz 1200 Hz) by means of an inverter bridge. The square wave output of the bridge is supplied to a specially designed external welding transformer equipped with a center-tapped rectifier output to supply a DC voltage to the resistance welding secondary circuit.
4.1.5 High-Frequency I)irect Current (H FDC)
HFDC controls rectify the 50/60 Hz power line input to create an output of more than 10 kHz by means of an inverter bridge. The square wave output of the inverter bridge is supplied to a welding transformer, which may be internal or external to the welding control, equipped with a center-tapped rectifier output to supply DC voltage to a resistance welder secondary circuit.
4.1.6 Stored Energy
Electrical energy is accumulated within the control at a slow rate using electrostatic (i.e., capacitors), electromagnetic (i.e., inductor), or electrochemical (i.e., battery) means before it is released at a relatively high rate to the resistance welding transformer or welding circuit.
4.2 Special Purpose Control Configurations
4.2.1 I)ual Gun / I)ual Schedule Control
This control configuration is used to operate two separate welding units, which are most commonly resistance welding guns. The initiations are interlocked to prevent operation of the unselected welding unit, while the selected initiation circuit is closed. At a minimum, independent valve outputs, weld heat and weld times are provided for each welding unit. Independent control functions may be provided for each welding unit.
4.2.2 Dual Guii / I)ual Sequence Control
The Dual Gun/ Dual Sequence configuration is similar to the Dual Guii/Dual Schedule configuration except a complete set of independent control functions is furnished for each channel. These controls may provide a separate welding contactor (e.g.. SCR contactor) for each welding unit and each may weld concurrently.
4.2.3 Load I)istrihution Control (IA)C)
A control system intended for use with resistance welding machines having two or more welding transformers. The LDC is configured to distribute the load by energizing the welding transformers individually in sequence on one or more phases or simultaneously on two or more phases.AWS J1.1M/J1.1 pdf download.