1. Double welding on one side: When feeding power from one side, try to weld two points at the same time to improve productivity. Single-sided feeding is usually ineffective separation, wasting electric energy, and welding cannot be performed when the point distance is too small.

2. Single-sided welding: When the electrode accessibility on one side of the part is poor or the part is large. When the secondary circuit is too long, this solution can be used. When feeding power from one side of the weldment, consideration should be given to adding copper pads on the other side to reduce separation and act as a fulcrum for recoil.
 
3. Double-sided single welding: All general-purpose welding machines adopt this scheme. Power is supplied from both sides of the weldment, which is suitable for welding small parts and welding spots around large parts.

When welding sheet metal parts, the following principles should be followed:
① Minimize the length of the secondary circuit and reduce the space included in the circuit to save energy;
② Minimize the ferromagnetic volume extending into the secondary circuit, especially to avoid large changes in the insertion volume when welding different solder joints. In order to reduce the fluctuation of welding current and ensure the quality measurement of each point (when using power frequency AC).