A new control for middle frequency resistance spot welding systems (RSWS) is presented in the patent. The discussed RSWS consists of a three-phase input rectifier with dc-bus, H-bridge inverter, welding transformer with single primary and two secondary windings, and output rectifier with diodes connected to the transformer’s secondary windings. The proposed control is based on two synchronously operating hysteresis controllers. The first one, the iron core flux density controller selects the polarity of H-bridge inverter output voltage that supplies the primary winding of the welding transformer. The second one, the welding current controller switches the selected voltage on and off. The flux density hysteresis controller changes the polarity of transformer’s supply voltage whenever the iron core flux density approaches saturated region. The welding current hysteresis controller switches the selected voltage off when the welding current exceeds the pre-set upper bound and switches the transformer’s supply voltage on when the welding current drops under the pre-set lower limit. The described control system makes possible reduction of transformer’s iron core and increase of transformer’s power.
COBISS.SI-ID: 15194902
This paper presents a pulsewidth modulation (PWM) algorithm for a three-phase ac-dc rectifier, where the third and fifth harmonics are indicated in the input phase voltages. A mathematical analysis, which includes this voltage harmonic's components, shows that the unity input displacement factor (IDF) can be reached by appropriate evaluation of duty-cycle functions. A PWM algorithm is proposed based on this developed theoretical achievement. This approach enables current sensorless unity IDF rectification. The PWM algorithmis investigated theoretically and verified by simulations and experiment.
COBISS.SI-ID: 15236630
The chapter presents a new Artificial Neural Network (ANN) based method for detection of saturation in the iron core of a welding transformer. The only required ANN input signal is the measured transformer's primary current. The ANN is trained with measured and calculated results. The proposed method can replace the iron core flux density sensor required in realization of advanced resistance spot welding system control proposed in the European Patent EP 2 097 912 B1.
COBISS.SI-ID: 15181334