Explaining the Control Principles of Various Control Modes of Mid-frequency Spot Welding Machines

There are four control modes for mid-frequency spot welding machines: primary constant current, secondary constant current, constant voltage, and constant heat. Here’s a breakdown of their control principles:

Primary Constant Current:

The device used for collection is a current transformer, installed in the primary main circuit of the welding transformer.

The controller detects the primary current value of the transformer through the current transformer, compares it with the set value, and automatically adjusts the conduction angle of the thyristor through internal calculation to keep the primary current of the transformer constant, thus achieving a constant welding current.

Secondary Constant Current:

The sampling device is an induction coil installed in the secondary circuit of the welding transformer.

The controller detects the secondary current value of the transformer through the induction coil, compares it with the set value, and automatically adjusts the conduction angle of the thyristor through internal calculation to keep the secondary welding current of the transformer constant by adjusting the primary current of the transformer.

Constant Voltage:

The sampling device directly samples internally and measures the primary voltage of the welding transformer.

When the controller is operating, it detects the primary voltage value of the transformer and compares it with the set value. After internal calculation, it outputs trigger pulse signals to automatically adjust the conduction angle of the thyristor to keep the primary voltage of the transformer constant.

Constant Heat:

Various sampling devices can be used for constant heat control.

When controlling for constant heat, the current set value is a percentage of the total power of the welding transformer. The controller calculates the required conduction angle based on the set value and sends out trigger signals. When the grid voltage fluctuates, the controller automatically adjusts the conduction angle of the thyristor to fine-tune the current output and maintain a constant output power.

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