Imagine a reliable transformer with a fuse that will not trigger despite frequent switching on and off. To make this scenario a reality, we have developed a transformer switching relay completely cutting out - not just reducing - the switch-on surge in your transformer.

Transformer Switching Relays

Using the soft starting procedure developed and by FSM AG, one or several single-phase transformers can be switched during no-load operation or under load without starting current surge (inrush). Your advantage: transformers can be designed in a more cost-efficient and low-loss manner.

Where transformers have to be switched more frequently and where the waiting time between the switching procedures resulting from the use of starting current limiters cannot be tolerated, transformer relays are used. Furthermore, transformer relays are used in case of socalled half-wave failures of the mains voltage. If the same must not result in the fuses triggering, a transformer switching relay from FSM is the correct solution.


Transformer switching relais from FSM AG are used in industrial sector, medical engineering, traffic and railway engineering, special-purpose vehicles, switchgears, electric heaters (chairlift), lighting technology,  broadcast technology and research. Additionally they can be used for any type of transformer. Transformer switching relays ensure your devices comply with the latest EMV regulations and standards for medical devices. We work together with multiple manufacturers of transformers to provide the best solutions possible.

Here you find some examples of applications:

Lighting technology

Medical devices,
e.g. dialysis machines

Special vehicles,
e.g. for broadcasting 

Traffic lights


Using the soft starting procedure developed and by FSM AG, one or several single-phase transformers can be switched during no-load operation or under load without starting current surge (inrush). Our product range includes: 

  • Easy to install
  • Guaranteed switching
  • Medical devices


  • Guaranteed switching
  • Robust
  • High power


  • Affordable
  • Fast Switching
  • Low maintanance


  • Fast switching 
  • high power
  • low maintanance


  • Compact design 
  • Affordable
  • Medical device



Our high quality standards

As part of our ISO 9001 and ISO 14001 certifications, we have a quality and environmental management system for developing, manufacturing, testing, and selling mobile energy supplies, pressure measurement technology, and transformer relays. Our high quality standards define us and differentiate us from the competition. 

To us, quality means:

Excellent workmanship

Long product service life


Safe electronics

Competent customer service

Download ISO-Certificates
REACH Statement

FSM AG is a manufacturer and trader of products, which are products within the meaning of the laws governing chemicals. We primarily buy the products from European suppliers, but in individual cases also from suppliers outside of Europe. According to the requirements of the REACH Regulation, we are therefore not subject to any registration obligations. This also particularly applies, because no chemical substances are released from our products, under normal or sensibly predictable conditions of use (see art. 7 para. 1 the REACH Regulation).

It remains to be said, that the products that you buy from us, are not subject to registration, as products in the sense of the REACH Regulation.

The chemical substances contained in our products, which may be subject to registration, must consequently only be registered by our pre-suppliers.

We are in close contact with the suppliers of relevant products, which are processed in our products, and are informed whether listed SVHC substances above 0.1% volume are contained, in accordance with the REACH Regulation art. 33. Furthermore, we will inform you immediately, in accordance with the REACH Regulation art. 33, if ingredients in our products (from content of > 0.1% volume), are rated as of very high concern by the European Chemicals Agency (ECHA).

From today's point of view, in light of the information from our suppliers, it should not be expected that our products contain SVHC substances, in a volume concentration above 0.1%.


Short Portrait

FSM AG develops an produces intelligent electronics. We support our customers with electronic products in the disciplines mobile energy supply, measuring systems and transformer switching relays as well as in the area of electronic manu­facturing services (EMS). Our products are mostly customized solutions and become part of a final product. Therefore one encounters the technology of FSM quite often without knowing that major components of the final product originate from us.

For further information please refer to our brochure

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