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.
F.06 Development of a new product
COBISS.SI-ID: 15194902The tester and the testing procedure for the evaluation of magnetic circuits are based on a pulsed excitation and a primary current hysteresis controler. Based on the frequency of system operation and reactive power, the magnetic characteristics of the tested core can be evaluated. By changing the primary winding, switching current and supply voltage an appropriate operating point and the range of tester operation can be determined. The testing procedure does not require any expensive measuring equipment and can be implemented with the existing supply of magnetic cores. The testing of the magnetic cores is fast, efficient, and universal. Even allready installed magnetic cores can be tested. The testing procedure can evaluate the entire magnetic circle, which is influenced by several factors, such as applid material, damages, air gap treatment, structural defects, etc.
F.10 Improvements to an existing technological process or technology
COBISS.SI-ID: 18795286Monitoring system for welding transformer is capable of taking measurements and recording data of electrical variables of a welding transformer. The collected data can be transferred to the PC, converted into DEC code and evaluated. Based on the obtained data, the operation of welding transformer during its life span can be evaluated whiles in the case of failure a diagnostic procedure can be performed. Monitoring system consists of a micro controller (PIC), FLASH memory, thermistors with adjustment circuits and additional circuits for voltage measurements on rectifier diodes, circuit for measurement of transformer's output voltage, circuit for measurement of welding current, input filter, energy capacitor, voltage regulator and two signal LED diodes. The micro controller is connected with FLASH memory chip through SPI bus. Computer can be connected with micro controller via USB/SCI bus.
F.08 Development and manufacture of a prototype
COBISS.SI-ID: 18535446Patent consist of two parts: The first part of the patent describes the iron core saturation detection with a measuring bridge. The measuring bridge detects the displacements of magnetic field in the welding transformer iron core, when the core is saturated. The patent describes the discrete electronic circuitry of the measuring bridge, capable of detecting the iron core saturation in a very short time, despite the present interferences. The signal from the circuit can be used for the control of the spot resistance welding transformer system in such a way that iron core saturation can be avoided and allowing the iron core to be to fully exploited. Hence, the dimensions of the iron core, for the same power, can be smaller. The second part of the patent describes the improvement of the Advanced Hysteresis Control (AHC) algorithm already protected by patent EP 2 097 912 B1. The disadvantage of the existing AHC algorithm is that it may cause the short pulses, which may have the negative impact on the resistance spot welding system. The proposed enhancement of the algorithm completely excludes the possibility of the occurrence of these pulses. The algorithm constantly compares the values of welding current and magnetic flux. Considering the concurrent states of both variables, algorithm predicts the possible irregularities and using the predefined switching patterns controls the inverter in such a way to prevent appearance of short pulses. In this way, harmful short time pulses can be avoided.
F.07 Improvements to an existing product
COBISS.SI-ID: 19217942By increasing the share of photovoltaic power plants in the electricity network, the impact thereof increases as well. Photovoltaic power plants may have a negative impact, primarily on the distribution network. Rapid transitions of clouds cause rapid changes in the output power of photovoltaic power plants, which can cause fluctuations in the voltage, which is not the best for network elements. Currently, there are two effective solutions, namely network reinforcement and the installation of energy storage devices. Both have a negative feature, which is a very high price. The doctoral dissertation presents, designs and develops, up to the level of a functional prototype, a solution that does not produce rapid changes in the output power of photovoltaic power plant. The essence of the proposed solution is to prevent the emergence of rapid changes in the output power of photovoltaic systems, and therefore the mitigation of the consequences, which is typical for existing solutions, is not necessary. The entire system consists of a cloud forecasting system, managing individual micro inverters, reactive power generation, and a car charging station to compensate for disturbances. A functional prototype of the system for cloud passing forecasting, managing individual micro inverters and generation of reactive power has been developed. The system was tested on an experimental photovoltaic power plant, equipped with a data acquisition system which provided the results of the measurements. The presented system was simulated in the scope of a distribution network model in order to evaluate the impacts of the photovoltaic power plant operation on a low voltage distribution network. Simultaneously, active participation of car charging stations in the mitigation of transients caused by photovoltaic power plants was tested. A cloud passing forecasting system prototype that provides information on when the cloud will cover the sun was built. The camera with appropriate optical filters and with a processor card appropriately processes the captured photos and makes forecasts of cloud passing. The built-in algorithm is computationally unproblematic, which enables low-cost production. The system allows predictions of cloud passing within one minute so that it can start a specific time before the passage of the cloud gradually reduce the output power of the photovoltaic power plant. Instead of a step change in the output power, a programed change predefined time constant in output power is achieved. An algorithm for managing such a power plant is designed so that it does not cause interference to the network. The algorithm ensures that all transients have entered the desired time constant upon arrival of the cloud and when the cloud moves away, the photovoltaic power plant does not cause rapid changes in the output power. The system is low cost and does not represent a significant additional cost for the installation of a photovoltaic power plant for net self-sufficiency. Photovoltaic power plants can additionally help the network by participating in the generation of reactive power according to the needs of the network. The dissertation presents an algorithm for the distribution of reactive power among individual micro inverters within one power plant so that the total output active power is maximized. The algorithm takes into account the current values of the working power of the individual microwaves and the efficiency characteristic. In networks where major voltage changes occur in a short period, car filling stations can be of a further assistance. It has been simulated in the dissertation that, by temporarily adjusting charging power, the car filling station has a positive influence on the voltage profile of the low voltage distribution network. During transients it temporarily decreases and then gradually increases the charging power. The fully developed cloud passing forecasting system with micro inverter control was tested at the mic
F.08 Development and manufacture of a prototype
COBISS.SI-ID: 21233174