Real-Time Compensators for Individual PFC of Single-Phase Welding Machines
KMT type compensators are designed for individual power factor correction of single-phase spot and line welding machines and other single-phase loads, characterised by abrupt power consumption changes. For welding time, the compensator is switched on by means of thyristor switch (water or air cooled). The control system of the switch guarantee: switching on of the compensator in time not longer than 1 period (20ms), excluding transients during capacitive circuits switching on
During interval in operation between welding processes, the controller maintains positive value of network voltage amplitude on capacitors' terminals. Switching on the capacitors is executed in the moment of equalising the network voltage waveform value with value of voltage on the capacitors. Switching off is executed when compensator's current waveform is zero crossing.
Welding machines generate current harmonics (very wide spectre with significant presence of 3rd and 5th harmonics), so the compensator has to be equipped with series reactors, which together with capacitance of capacitors makes a resonance circuit of resonance frequency 135Hz.
KMT type compensators can operate with machines of minimum operating time 0,06s (3 periods).
Beside power factor correction, KMT type compensators limit currents consumed by welding machine (up to 3 times) and voltage drops during welding.
Rated power of the compensator and parameters of apparatuses and equipment are chosen individually for specific welder on basis of following informations:
- rated power,
- maximum power,
- maximum operational power,
- rated voltage,
- rated frequency,
- type of supply,
- minimum welding time,
- interval time,
- welding current (secondary),
- peak current (primary),
- continuous current (primary)
