3-phase medium voltage AC breaker

Reliable over current and short-circuit AC grid protection

The ultrafast solid-state 3-phase medium voltage AC breaker. Designed to open one or several phases of an AC-circuit within microseconds. It effectively avoids high current levels in case of a fault or short-circuit event. If installed at the connection point between a smart-grid and the main grid, it minimizes the impact of microgrid-internal short-circuits on the main grid. The connection point is simply opened before a short-circuit pulls down the grid voltage.

Additionally the technology is based on the most advanced and powerful press pack-IGBT technology, brought to its best performance by Astrol’s unique control technology. Besides, you can configure the AC Breaker for different current and voltage levels with it’s modular design.

Advantages of solid-state breakers compared to mechanical breakers

Solid-state circuit breakers offer significant advantages over mechanical breakers in terms of switching speed, lifetime, and safety. Their rapid response time, long operational lifetime, and advanced safety features make them ideal for a wide range of high-performance applications, from pulsed power systems to industrial automation and renewable energy installations.

Switching speed

Some applications require an immediate current interruption. Even the switching times of the fastest mechanical circuit breakers are not fast enough for certain applications. Particularly in low inductive circuits, fault currents can reach dangerous levels within milliseconds. The solid-state switches from Astrol are in a different league because their switching time is more than a hundred times faster than mechanical switches are. The reason for this greatly improved switching time is the fact that no moving contactors are required to switch the switch between conducting and blocking states. The breaking time clears fault currents before they reach high values. In this way, the connected devices are optimally protected and greater voltage stability is achieved.

Conversely, the semiconductor switches enable the system integrator to design low-inductance networks. Additionally, better protection of the equipment against short-circuit currents, improved voltage stability and greater design freedom for the system integrator are the main reasons for customers to rely on our semiconductor technology.


The fact that Astrol’s semiconductor-based switches interrupt the current without moving parts not only has the advantage of faster switching speeds, but also less material wear. Electrode burn-off is an unavoidable side effect of mechanical switches, which is non-existent with Astrol’s solid-state switches

Because the carefully designed protection of the built-in semiconductors against overvoltage and overcurrent, invisible to the outside observer, allows the breaker to operate continuously without wear, even in applications with frequent switching. The significantly extended maintenance intervals of semiconductor-based switches compared to mechanical switches is the most important argument for customers to rely on Astrol’s solid-state technology when the application involves frequent switching of high currents.


Another important advantage of a switch without moving electrodes is the absence of arcing. In hazardous environments, such as in the chemical industry, hydrogen production or coal mining, arcing in protective devices is an avoidable risk. Solid-state switches use semiconductor elements to switch between conducting and blocking states instead of opening gaps between the electrodes that cause arcing.

Overvoltages caused by stray inductance are also dissipated via semiconductors. As a result you get completely arc-free interruption of currents, even in the worst fault scenarios. The added safety is a key argument for customers with hazardous environments to rely on Astrol’s semiconductor switching technology.

Why Astrol solid-state 3 phase AC breakers?

Engineered with state-of-the-art technology, our circuit breaker guarantees unparalleled speed in interrupting medium voltage currents, ensuring swift and precise operation in critical applications. Not only does our product boast unmatched performance, but it also offers substantial cost savings through significantly reduced maintenance requirements. With arc-free switching capabilities, Astrol’s circuit breaker minimizes the risk of electrical hazards and ensures the safety of personnel and equipment. Trusted by industry leaders, our technology is proven in over 100 of breakers currently in operation worldwide.

What sets us apart is our commitment to quality from design to manufacturing. All components and subsystems are meticulously crafted in-house at Astrol, eliminating spare part and obsolescence-related issues commonly encountered with outsourced solutions.

Benefits of our 3 phase solid-state AC breaker

  • Fastest available medium voltage circuit breaker
  • Significantly reduced maintenance cost
  • Arc-free switching
  • Proven technology in over 100 breakers in operation
  • Design and manufacturing of breaker and subsystem in-house at Astrol
  • No spare part and obsolescence related problems

Standardized AC breaker, main specifications

  • 3-phase 300A – 1 kA (up to 3kA possible in customized design)
  • Voltage classes from 1kV to 11 kV ( up to 60kV possible in customized design)
  • Liquid cooling
  • IP Protection IP20 (different IP ratings available upon request)
  • Ambient temperature range: -25…+60°C

Smart protection of your microgrid

The Astrol AC Breaker is system independent and can be integrated in any type smart grid on the medium voltage level. Seeing that it constantly monitors current and voltage on all three phases and reacts autonomously according to predefined settings.

Best in category di/dt capability allows ultra-fast switch-off

Mechanical Design

The AC-Breaker is installed in a cabinet with access from the front side for maintenance. The modular design allows the use of standardized electrical and mechanical components for different current and voltage ratings. All components are UL94 certified, and vibration tested according to IEC 60068-2-6.

Electrical design

The electrical design uses press-pack IGBT modules, which are connected in series to voltage levels of up to 60kV rated voltage. By over-designing the IGBT-stack and adding more IGBTs in series than required by the system voltage rating as a minimum, redundancy can be added according to the specific requirements of each project. The number of Press-Pack IGBTs in parallel defines the rated current, which can go up to 3kA per phase. The MOV circuit is dimensioned and optimized for each application and depends on the system inductance of other electrical parameters. With the Astrol AC-Breaker, the grid integrator enjoys maximum design freedom.
press pack IGBT

Control interface

The controller of the breaker and the direct optical link between several breakers manage short circuit protection of healthy zones without protocol overhead.
For switching actions controlled by the overall system controller, the DC-Breakers provides different communication interfaces:

  • Optical (Glass or Plastic)
  • Modbus-TCP, Profinet , WEB based
  • Wire Bus System with CAN and RS485
  • 24V power supply with internal filter module

Parametrization and customization

The AC-Breaker provides application specific parametrization. Short-circuit and over current detection can be adjusted according to customer specific requirements.
A customized AC-Breaker can be either an adaption an existing version or a fully new design.
Typical items for customization are:

  • Communication to overall controller
  • Internal or external cooling
  • Quick coupling connectors in the water-cooling circuit
  • External fan control with PMW

Pre-charge / Pre-magnetization unit

This optional unit is comparable with the balancing switch of the Marine DC breaker, as it also avoids inrush currents through the breaker when the breaker is switched on. In a 3-phase microgrid, it is typically used to pre-magnetize transformers prior the closing the AC-Breaker. The pre-magnetization unit is designed according to the voltage rating of the breaker and includes a solid-state switch and a project specific resistor for each of the three phases.

3-phase MV AC breaker platform

We have a standard 11 kV model 500 A phase current and 6.6 kV model 500 A phase current standard model. Further voltage and current ratings available upon request.

3-phase medium voltage AC breakers

At Astrol, we are more than just a design partner. With our commitment to quality, innovation, and customer satisfaction, we are your long-term collaborator in success.

Astrol long-term collaborator

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