B-14

STT WAVE SHAPING PRINCIPLES

Appendix B

B.6 SECONDARY STT WAVEFORM COMPONENTS

NOTE: The Invertec STT power source circuitry automatically establishes proper values for most primary and secondary waveform components. The values can be adjusted, but should not be set far from their automatically set values.

B.6.1 PINCH START

The pinch start is the amperage setting that begins the ramp up to the maximum pinch current. Pinch start current must exceed background current.

B.6.2 PINCH/PEAK

Pinch/Peak is the ratio of maximum pinch current to peak current. This parameter is used to establish the desired maximum pinch current value.

B.6.3 PEAK TIME

Peak time is the duration of the plasma boost period (peak amps) in milliseconds. The duration of peak time is typically set from 1 to 2 milliseconds. Longer peak times may cause weld spatter.

B.6.4 dV/dt DETECT

The dV/dt detect setting determines at what point in the necking down process pinch current will be discontinued.

WAVE DESIGNER

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Lincoln Electric IM649 manual Secondary STT Waveform Components, Pinch Start, Pinch/Peak, Peak Time, 4 dV/dt Detect