What does Power Supply Technology mean?
Power Electronics "perform" something, electric energy is being transformed while the electric parameters such as voltage, current and frequency are modified to accumulate energy, to adapt energy for an optimal transmission or to transform energy into mechanical energy, as it is done in motors. By using switching power semiconductors in connection with passive components, like capacitances and inductances, an adequate converter is constructed. The efficiency to target should be the highest possible. The efficiency achieved by power electronics is often higher than in conventional processes. Therefore, the application of power electronics as an active energy-saving method contributes substantially to environmental protection. If e.g. pumps and ventilation systems are operated by an inverter with a variable driving speed, energy consumption will considerably be reduced.
Range of Performance
When developing an electronic assembly we cover the total range from new conception via hardware and software design through to prototype construction and initial operation.
Due to the fact that we keep the information about customized developments in confidence, we are unfortunately not able to give any details about the numerous reference projects.
In order to give you a summary of our activity range, we will describe some selected projects in a general way, without mentioning customers' name or technical details.
Inverter for AC Motors
An inverter is needed to start a three-phase AC motor smoothly and to operate it at a variable speed. Due to the usage of inverters, noise can be reduced and energy can be saved.
If environmental conditions or particular functional properties impose special requirements on the inverter, implementing standard components is difficult. This requires an adaption or redevelopment in consideration of the customer's needs.
Combined with a suitable software, an inverter can also be used to operate generators or as a grid connection.
Power Electronics in Vehicles (Automotive)
Due to the fact that power supplies have to resist specific vehicle conditions (temperature, dirt, vibration) and installation space is often very limited, compact and solid components are necessarily required.
In case of hybrid- or pure electric vehicles the challange is to electrify all functions previously driven by a conventional combustion engine. This concerns, besides the drivetrain components, also several further auxiliary systems. From air condition to power steering - they are also driven by three-phase AC motors and inverters.
The alternator is substituted by a DC/DC converter which ensures the energy flow between the different DC systems and voltage levels. Whereas small consumers are still provided with 12V or 24V, loads with higher power demand are connected to the high voltage circuit.
The electronic components require a software adequately matched to the vehicle's features. Communication is generally ensured via CAN-bus and includes extensive diagnostic functions.
Active Front End Inverters for Renewable Energies
Energy produced by wind turbines and in solar parks is fed into the public electricity grid. For this purpose, active front end inverters of variable outputs are necessary. In order to guarantee stability of electric supply, the various specifications of grid operators are to be observed. As a result the active power at too high mains frequency can be limited, especially reactive power to increase or to reduce supply voltage is fed in. Also in case of a faulty grid, a well-defined conduct (e.g. LVRT) is imperative.
Static Frequency Inverters for High Voltage Cables and Large Power Transformers
High voltage cables for energy transfer as well as large power transformers of up to 500 MVA must be tested by the producer in different ways. For this purpose, AC voltages with different frequencies are required. In case of cable tests, these are lower frequencies (<10 Hz) due to bigger capacities, in case of transformers these frequencies can increase up to 200 Hz.
Rotating converters which were used in the past can be substituted by static frequency inverters. Performance often amounts to several MVA. A very small THD and a low interference level are required to enable sensitive PD measurements of the test objects.
Power Electronics for Medical Technology
For the operation of x-ray tubes a high DC voltage of approx. 100 kV at a current of some mA is required. This high voltage is generated by a special switching converter which
precisely controls the voltage by clearly defined on-off switch points. The transformer as well as the high voltage component is generally operated in a single-tank filled with insulating oil.
Powerful battery systems are mandatory for electromobility. For this purpose numerous cells have to be connected in series. In order to achieve an optimum output within a maximum service life, the cells should only be operated within a defined range. Considering that, it is necessary to measure voltage, current and temperature of each cell to enable individual adjustment of the current state of charge. For this reason, a battery stack needs a so-called "balancing". The battery management communicates with the charger or the DC/DC- converter, which connects the battery to the system voltage (intermediate ciruit voltage).
High Efficiency with Resonant Converter
The efficiency of a power electronic converter is considerably determined by switching losses. There is a trade-off between low switching frequency with low switching losses and high switching frequency together with smaller inductive components.
By means of resonant converters switching losses are significantly reduced, due to the fact that at the moment of switching either current (ZCS) or voltage (ZVS) is reset to zero. For the construction of resonant converters a specific topology in connection with special control processes is generally required.
This effort is rewarded by achieving a high efficiency within a compact and inexpensive assembly. At the same time interference emission is generally reduced, which leads to a limited necessity of filtering.
Today many installations are configured as distributed systems, where a number of components communicate with each other via fieldbuses and share information. As the most common user interface, the PC is ideally suited to evaluate and show this information. Regardless of whether graphic displays or data loggers are involved - or operator functions, such as monitoring, open loop and closed loop control functions - there are many design options for user software tailored to your installation.