Forschungsteam für kundenspezifische Lösungen

What are thermal protectors?

Temperature limiters are fitted as safety devices into electric motors, heaters and transformers for popular brands of domestic appliances. They are often known as temperature controllers, temperature monitors or safety temperature limiters.

A distinction is made between normally closed (NC) and normally open (NO) thermal protectors. Conventional protection devices generally feature NC thermal protectors, but NO thermal protectors are more suitable for ensuring that a device operates safely, reliably and without interruptions.

Thermal circuit breakers are typically used in electric motors, transformers, heating devices and conventional household devices such as mixers and kettles.

Thermik specialises in developing and producing bimetal thermal protectors. But our product range also includes PTC motor protection sensors and resistors as well as customised PTC heating elements. Products from Thermik are primarily used in the household device industry and in special applications in the automotive sector. They protect components and end devices from overheating due to excessive stress.

 

The temperature limiter - how it works

In order to measure and regulate the temperature in various electronic devices we use the properties of bimetals. Simply described, a temperature limiter is a mechanical circuit breaker which has two or more internal contacts, one of which is fixed whereas the other is moving. This is attached to a bimetallic disc which due to its material properties is able to expand and contract. When the temperature increases to its maximum permissible level, the expansion of the bimetallic disc disengages the moving contact from the static one and results in an interruption of the contact. As the appliance cools down again the disc of the temperature monitor cools down with it and returns to its original form - contact is re-established and the circuit is closed. 


Temperature regulation with thermobimetals

Under bimetals one understands thermoplastic sheet metals which consist of two metals having different material properties. Since metals react to changes in temperature (this characteristic is expressed by their coefficients of thermal expansion) they are eminently suited for utilization in temperature regulators. To manufacture bimetals, two metals with differing coefficients of thermal expansion are combined: they are rolled onto each other under high pressure, thus becoming inseparably joined to each other. Depending on their composition bimetals have differing rates of expansion which result in different degrees of curvature. Principally one metal expands more than the other whereby the combination expands in a predetermined direction. The rate of expansion and hence the curvature is dependent upon the temperature level. The bimetal always forms a curve in the direction of the metal which expands the most.     

Customised solutions for thermal protection

Thermik has been a reliable innovation partner to renowned brand manufacturers for many years, developing thermal protection solutions and supplying them directly to customers. We rigorously examine and analyse products, processes and the desired application every time we develop a new solution. The aim of executing ground-breaking ideas and transforming them into cutting-edge, long-term solutions for our customers is what motivates us every day.

Our engineers are constantly chasing new, innovative ideas with great ambition in order to find the perfect solution. Our passion for technical innovation and high quality has driven us to become the supplier with the largest number of customised thermal protection solutions in the world. Furthermore, our decades of experience in the thermal protection sector have made us an attractive development partner for renowned customers from the drive technology, aviation, aerospace and automotive industries.

“Someone has to lead the way. Someone needs to be first to transform their expertise into better ideas. Courage is needed for success. This is the only way to make progress.”


Marcel P. Hofsaess,
Managing Director

Individual thermal protectors – Process chain for our customised solutions

Improved switching behaviour and longer service life

Conventional systems in thermal protectors

Conventional thermal protectors do not feature additional spring discs. As a result, contact is made gradually, creating a risk of an arc flash.

Advantages over conventional protection devices:

  • More protection thanks to current-free bimetal
  • Improved switching behaviour thanks to additional spring disc (no premature switching)
  • Optimal thermal protection thanks to precise switch behaviour
  • Significantly less contact erosion
  • Less contact wear
  • Significantly longer service life

The Thermik system

The function and switching behaviour of Thermik thermal protectors, featuring an additional spring disc (yellow), ensure that the bimetal disc (red) is continuously active.

What is the advantage of using a continuously active bimetal disc?

Bimetal discs are subject to an ageing process that cannot be avoided. This changes the function parameters of the discs, depending on their load capacity and life cycle. The parametric stability of these discs can only be improved by reducing the mechanical stress.

Only continuously active discs are used in systems from Thermik, since continuously active bimetal discs are generally subject to less mechanical stress than discontinuously active snap discs.

Current self-heating: Typical switch behaviour of a thermal protector with a current-carrying bimetal disc (a) compared to thermal protectors with a non-current-carrying bimetal disc (b) in a high-current application.

Force/displacement diagram (characteristic curve): a) simple spring disc (linear), b) spring snap disc (non-linear).

Advantages of systems with continuously active bimetal discs:

  • Increased work capacity
  • Greater contact stability/contact pressure
  • More efficient use of space thanks to the circular design (miniaturisation)
  • Simple geometry: capable of bearing more mechanical stress
  • Cost-effective production (simple tools)
  • Longer service life
  • Better long-term stability
  • Lower contact resistances
  • More precise switching point accuracy
  • No premature switching
  • Very precise switching point response to ambient temperature only

Premium protection devices

The most reliable, cutting-edge technology

Our quality standards play a role long before we even begin to develop and manufacture our products. We use only the most sophisticated materials to make our protection devices. We insist on using precious metals for Thermik products, due to their superior electromechanical properties. Experience has shown that the quality of our precision engineering cover parts cannot be reproduced outside of Europe.

Therefore, Thermik customers can count on the fact that they are working with a high-quality product wherever they are in the world. In choosing our products, customers ensure that they receive the best and most reliable thermal protection technology that is available in the world.

A selection of thermal protection devices:

    • Round thermal protectors
    • Flat thermal protectors
    • Pressure-resistant thermal protectors
    • Sealed thermal protectors
    • Current-independent thermal protectors
    • Temperature-sensitive thermal protectors
    • Defined current-sensitive thermal protectors
    • Voltage-retaining thermal protectors
    • Interlocking insulation shrink caps
    • Thermal protectors on a tape
    • High-temperature thermal protectors
    • Hybrid thermal protectors
    • Arc-free thermal protectors
    • And many more.

    In-house developments from Thermik

    The most reliable when it comes to safety

    Developing customised solutions is one of our specialties. This is also why the product range from Thermik, manufactured in-house, is the largest and most diverse of its kind. No other supplier in the world offers such high quality or such a wide-ranging portfolio of standard products and customised solutions.

    We use state-of-the-art technology to design, select the materials for and determine the material composition of each of our products, for which we hold numerous German and international property rights. This demonstrates the unparalleled reliability of solutions developed by Thermik when it comes to safety and quality. This crucial competitive advantage benefits not only us but also our customers.

    Process chain for our in-house developments

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