Controls & Transformers

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Questions and Answers

High frequency welding offers weight reduction and plant power reduction but let’s look at this a little closer. Other benefits in control can also be realized.

If one were to design a weld, the control must provide functions such as squeeze, weld, hold and off. It does this by communicating with the cylinder or servo valve, the SCR or IGBT and or the NC device running the weld cell.

DC and AC welding have been used for years but recently inverter technology has become a very large factor in the resistance welding industry. So let’s look at frequency and where it is used in resistance welding technology.

Inverters are three phase devices and operate at very high frequencies. SCR are not used as the switching devices in these units. IGBT’s (Insulated-gate bipolar transistor) are used for this function. This power semiconductor device is used as an electronic switch. It is known for its high efficiency and fast switching.

As we know the AC weld is a sine wave with a positive and negative half cycle and a zero cross over where no power is transmitted. The inverter or mid frequency curve is a single direction with no cross over and provides power the entire time. There is more total power transmitted per unit of time.

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