How to distinguish between AC spot welder and DC spot welder?

Classification and identification of precision spot welders: DC and AC

Precision spot welders can be clearly divided into two categories: DC and AC according to their current characteristics. However, many people may not be very clear about the distinction between these two types of spot welders. Next, the editor of Huandian will explain the differences between them in detail from four aspects to help you easily identify them.

1. Comparison of welding quality

AC spot welders have a relatively long adjustment cycle. For a 50Hz power grid environment, the adjustment resolution of its welding time is only 20ms. In contrast, inverter DC spot welders show higher control accuracy, and their time adjustment resolution can reach 0.25ms (based on an inverter frequency of 4kHz). In addition, the response speed of inverter spot welders in feedback control is significantly faster, and the output stability is also better.

In terms of thermal efficiency, AC spot welders are affected by excessive current and have relatively low thermal efficiency. When using thyristors to adjust the current, if the current percentage is small, the zero-crossing time will be extended, further affecting the welding effect. The DC spot welder outputs pulsating DC current, which forms a continuous DC output under the action of loop inductance, with high thermal efficiency and stable welding heat input.

2. Comparison of welding speed

Due to the phenomenon of current zero crossing in AC spot welders, the heating time is relatively long. The inverter resistance spot welder uses DC output, which is more concentrated in heating, thus significantly shortening the welding time.

3. Comparison of energy-saving effects

The AC spot welder operates at a frequency of 50Hz, the transformer loss is large, the welding machine power factor is low, and the loop loss is also large. The inverter welder is different. Its transformer operates in a higher frequency range (1-5kHz) with minimal loss. At the same time, DC output also improves the power factor, making the energy-saving effect more significant.

4. Consideration of equipment volume and weight

The transformer core of the AC spot welder is relatively large, so under the same power conditions, the equipment appears to be bulky. The transformer of the DC resistance spot welder is greatly reduced, making the overall equipment lighter and more portable.

In summary, by comparing the welding quality, welding speed, energy saving effect, and equipment size and weight, we can clearly identify the significant differences between DC spot welders and AC spot welders. I hope this information can help you better choose and use the spot welder that suits your needs.

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