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Muuntosähkö Oy - TRAFOX

TRAFOX is a brand of Muuntosähkö Oy. 

The company develops, manufactures and customises high-quality transformers, chokes, filters and Trafox Superintend® monitoring devices.

TRAFOX -products and systems are used in various applications from heavy industry to health care.

Muuntosähkö Oy was founded in 1947 in Finland. The company headquarters is in Helsinki and they have production facilities in Helsinki and Joensuu (Finland), Viljandi (Estonia) and Suzhou (China).

With seventy years of experience, TRAFOX understand customers’ individual and field-specific requirements and is able to provide them solutions that create true added value. The starting point for TRAFOX product development is the diverse Trafox solutions, which meet both international standard requirements and customer-specific needs.

Trafox Superintend®

TRAFOX innovative fault current and insulation level monitoring devices are designed to cater for the needs of industrial, renewable energy, marine, medical, construction and heavy industrial applications.

Company's long experience for monitoring device engineering, continuous development work and utilization of the latest technology provides customers the best products that fulfil their specific needs.

In the design and manufacturing of Trafox equipments, great emphasis is placed on safety, operational reliability and environmental protection.

IMD - Insulation Monitoring Systems

IMD is the insulation level monitoring device for non-grounded electrical networks. The product line confirms to IEC measurement requirements for both healthcare and industrial applications. IMD-devices have been tested and certified for electromagnetic compatibility (EMC) and electrical safety. So the customers can plan the introduction of the devices without worrying about safety related risks.

The innovative measurement technology enables also the monitoring of DC power networks.

IMD - Measurement principle

IMD -Medical

IMD -Industry

IMD -Photovoltaic

NEW - IM 03 Industry

RCM - Residual Current Monitoring Systems

A fault current monitoring system for applications where special reliability is required from the power supply. Trafox Superintend® RCM monitors continuously the electric system’s fault current level and reacts immediately to a fault current surge.

With the fault current monitoring system, the fault current surge can be noticed before a safety device is triggered. This is beneficial especially in applications in which an unexpected interruption in power supply will result high expenses. The alert limit and delay of the fault current alert can be adjusted according to the application’s demands.

Trafox Superintend® RCM product family includes fault current monitoring devices with 1, 8, 16, 32 or 64 measurement points (channels). Multi-channel devices also record the minimum and maximum values of the fault current and the fault current alert history and these can be remotely accessed with a web browser from any location.

The benefits of the Trafox Superintend® RCM monitoring system:

  • Better fire- and personal safety due to continuous monitoring of fault current.
  • Predictability of insulation faults.
  • More precise locating of insulation faults is possible with a multi-channel fault current monitoring device.
  • Quick location of leakage currents deteriorating the electricity quality.
  • More reliable electricity system by minimizing interruptions in power supply.
  • Monitoring of load currents of zero and phase conductors and identifying possible overload situations in advance.
  • Up to 2048 monitoring points can be supervised with one web browser display.


Trafox - Medical Isolation Transformers

Medical isolation transformers are isolation transformers for earthed devices used in medical facilities. The transformers isolate and separate the connected device from the medical facility’s isolated electric power network. In addition, the transformers keep the leakage current of the devices within the limits set for medical devices.

KKS - Encapsulated isolation transformer and KKSA - Open style isolation transformer

Medical isolation transformers have been manufactured with strengthened isolation. The transformers’ leakage current between the primary and secondary windings is very low. The maximum leakage current without load at rated voltage and frequency is 0.5mA. There is an electrostatic shield between the primary and secondary windings.

A transformer used in a medical facility must be equipped with an insulation monitoring device. 

KKS and KKSA -Medical transformers

Trafox - Filters

Filters are required for filtering motor input voltage in frequency converter applications. Filtering extends motor service life, lowers the temperature and ensures better reliability of operation. The transformers are used in different kinds of industrial, construction, energy technology and marine applications, such as electric motors, compressors or cooling systems.

Trafox selection includes DU/dt and Sine filters. The features, dimensions, structure and mounting options of the filters can be tailored according to the customer’s objectives and needs. We are continuously developing our design, certification and manufacturing methods in order to respond to increasingly demanding challenges.

Trafox - Sine Filters 10 - 1460 A



Sine filters are used for filtering high frequency interference in the input voltage of a motor in order to achieve cleaner sinusoidal voltage. High frequency interference is a great risk for motor coil insulation and reliability.

These risks can be eliminated with Trafox Sine filters. By using the filter, the noise level of the system can be lowered. The extensive standard selection of different current ranges ensures an optimal filter choice.

The features, dimensions, structure and mounting options of the filters can be tailored according to the customer’s objectives and needs.

Sine filters 10-410 A

Sine filters 460-1460 A

Trafox - du/dt-Filters

du/dt -filters are used for filtering voltage increase rate and voltage peak value in motor input. With Trafox du/dt -filters, lengths up to 100–300 m can be reached, facilitating even the most demanding installations.

The extensive standard selection of different current ranges ensures an optimal filter choice.

The features, dimensions, structure and mounting options of the filters can be tailored according to the customer’s objectives and needs.

du/dt -Filters