Controls & Transformers
Questions and Answers
Weld controls have the capability to handle a modest number of machine control functions. They are capable of functioning as the weld control and machine control for small cells with a modest number of non-weld functions.
Reference: RWMA - Resistance Welding Manual 4th Edition
A valve transformer or valve power supply provides the low voltage power to activate the valve which controls the air to the pneumatic welding cylinder. This pneumatic cylinder is the source of force in the welding operation. This same transformer/power supply could send a signal to a servo to initiate its operation.
The weld control logic monitors all input information and stores all programs and initiates all necessary commands to complete the required functions. In simple terms when the input signal for a weld is received from the foot switch or other input source the control logic starts the squeeze/weld/hold/off sequence as programmed.
AC controls all have microprocessors that activate contactors to control the time and amount of power that is delivered to the part to be welded. These contactors could be considered electronic switches. They are made up of two SCR’s. There is one SCR for the positive and a second for the negative half of the AC sine wave.
A standard AC weld control is made up of a modest number of components each with a specific purpose. The major components are:
Disconnect
Welding Contactor
Weld Control Logic
Valve Power Supply
The Disconnect is a safety in case of an electrical failure.
The contactor is an SCR control device which controls the amount of power and time of power conduction.
The Weld control logic is a microprocessor unit which receives all external inputs and initiation signals and activates all sequences including the force and power.
The Valve Power Supply provides the low voltage and signal to the cylinder or servo unit for the force component of the weld system.
Reference: RWMA - Resistance Welding Manual 4th Edition
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