Power converter For use on land, at sea and in the air

Power converters are used in applications on land, at sea and in the air. They have to work reliably even under extreme conditions: wide temperature ranges, shock and vibration, electrical interference, electromagnetic compatibility (EMC) and sudden load peaks (load dump).

Reinhard Kalfhaus is the founder and managing director of SYKO

Power converters have been continuously developed for several decades. Experience gained from different circuit topologies and modifications is incorporated into new generations. Today, components up to the power range of around 10 kW can be produced in series, often with certifications according to common standards such as EN, MIL or VG, so that they can also be used reliably in safety-critical applications or under extreme environmental conditions.

Meeting the functionality needs of the consumer

In public transportation, power converters are used to provide an insulation-monitored supply of 230 V/50 Hz or DC voltage from the contact wire voltage of around 750 V. This can be used to supply charging stations for mobile devices, tools for service personnel or lighting and data transmission at remote stops. At the same time, they help to increase comfort and safety for passengers, avoid breakdowns during operation and reliably support the increasing number of additional electrical systems. Modern concepts also take into account aspects such as energy efficiency, small size and easy maintenance, so that the devices can be flexibly integrated into existing vehicles. With a view to future requirements, power converters therefore play a central role in the sustainable and safe operation of modern transportation systems.

Transmitting high power over long distances

The manufacturer Syko has recently had a system component certified that can transmit a potential-separated power of 3.3 kW over a distance of 3.3 km. The output side supplies a residual current and insulation-monitored voltage of 230 V_AC; optional variants for 28 V battery charging or three-phase 400/460 V connections are also possible. Such systems make it possible to disconnect platforms - even under water, for example - from the operator over longer distances with reduced power and still supply them with energy and communication. In another project, Syko processes a reverse-polarity protected 28 V on-board power supply voltage (16 to 34 V) and intercepts load-dump pulses of up to 100 V/50 to 280 ms without current reflection. This provides a battery or high-cap-supported voltage of 56 V/3.6 kW. Topologies such as the totem pole circuit for AC inputs, voltage-cascaded high-voltage regenerators for DC inputs, high-current synchronous rectifiers and combined buck-boost variants are used. The systems are controlled and regulated on a processor basis, which enables flexible interface adaptation.

Stability as a central goal in most projects

In the market for robust power electronics, the challenge lies less in completely new circuit concepts and more in the precise adaptation and combination of existing topologies. The requirements are particularly high in mobile environments - for example in railroad, defense or offshore applications: extreme temperature ranges from -45 to 85 °C, strong vibrations and short-term current jumps in the range of several thousand amperes put additional strain on the systems.

Suppliers in this segment often work with comparatively small to medium quantities. This makes production complex and increases the economic pressure, especially as development and certification processes are time-consuming and cost-intensive. To ensure reliability, extensive quality assurance measures are standard: temperature tests over several hours, dynamic cycle tests between -40 and 85 °C and documented functional tests from the prototype phase onwards. This practice ensures that new systems can go into series production with a high level of stability - even if this significantly extends the development time. Specific projects show how broad the range of applications for such power converters is. A high-cap charger, for example, charges a 55-farad/550-volt capacitor from 0 volts with an output of 3.6 kW, based on on-board supply voltages of 24 or 72 V. Communication takes place via bus structures so that the system can be integrated into complex applications.

Another example is a specific excitation device that generates a three-phase output voltage of 3.6 kW from a 110-volt on-board power supply voltage in an isolated manner in order to drive a synchronous motor via f/u control. During operation, the device can switch to a regulated DC excitation voltage.

The power supply from the 750 V contact wire is also one of the typical tasks. Here, a 28-volt battery charge with up to 2 kW is provided in an isolated manner. This includes the ability to absorb dynamic voltage peaks of more than 1,000 V in the millisecond range. In addition, a three-phase 400-volt output voltage of 500 W can be generated from the same source.

From modular system to customized solution

Other applications include submarine on-board electrical systems with static high-voltage voltages of 220 to 440 VDC, which are sometimes subject to severe dynamic fluctuations of up to 1,600 V. Converters with outputs of up to 5 kW are used here, which can switch between current and voltage operation. Smaller systems - such as a 24 V/500 W converter with IP67 protection - can also be cascaded to achieve higher outputs if required.

Such examples illustrate that development does not rely solely on standard solutions, but often requires customer-specific modifications. Digital control concepts and flexible interfaces help to implement requirements from specifications in a short space of time, while at the same time leaving scope for later adaptations, extensions and integration into complex overall systems.

In practice, the wide range of system components available means that project engineers can often fall back on existing solutions that only need to be adapted electrically or mechanically. This approach enables manufacturers such as Syko to implement even complex specifications in a comparatively short time.

In 2024, however, the downside of high demand also became apparent: the order backlog doubled, which placed a heavy burden on the organization. From purchasing materials to hiring staff and investing in infrastructure. Stocks and semi-finished products increased significantly, tying up capital in the short term. This phenomenon illustrates a challenge that many medium-sized companies are currently facing: They are considered economically sound, but can become temporarily illiquid due to sudden peaks in orders. There are also structural factors. Since the coronavirus pandemic, for example, changes in working habits, higher sickness rates and increased production costs have had a dampening effect. At the same time, investments in new capacities, such as the planned construction of a three-storey production building, are continuing. The balancing act between expansion and cost pressure is therefore becoming particularly acute. (mr)