QUALITY FIRST

Production

A strong strategic partner to our customers with profound and long tradition in automotive and industrial fields.

Quality

Providing technical support and specialist advice. Steadily investing into new top of the art machinery.

Innovation

A financially stable company, a part of a successful group. Continuously implementing improvements.

Vision 2025

Keko Varicon is going to introduce 2025 vision during the PCIM 2018 exhibition showing the great importance of Artificial Inteligence (AI) for the mankind. The upcoming Industry 4.0 is going to surpass all of our expectations.

Varistor’s main function is protection of electronic devices, which have important task in complex industry and
consequently in our lives as well, while EMI suppression components reduce electromagnetic noise below acceptable
levels.

What is a varistor?

Varistor is a variable resistor which depends on applied voltage (voltage – dependant resistor) with current – voltage characteristics similar to a diode.

Structure of a varistor

Predominant material used in production of varistors is Zinc Oxide (ZnO). Some additional oxides like Bismuth, Manganese and Cobalt are also added, therefore varistors are also called Metal Oxide Varistors or MOVs.

Why use a varistor?

To provide protection in electrical and electronic circuits. Electronic and electrical devices are designed to operate at a certain maximum supply voltage. Considerable damage can be caused by voltage that is higher than that for which the devices are rated.

Voltage across the varistor measured at a
given reference current In

Reference current.

The peak voltage developed across the varistor under standard atmospheric conditions, when passing an 8/20 μs class current pulse.

A peak value of current which is 1/10 of the maximum peak current for 100 pulses, two per minute for the 8/20 μs pulse.

Optimal solutions

Challenges are presented in everyday work and as such are part of business. This challenges can be seen as change in way of work – new technologies, or new products, but all challenges are possibilities for us to grow in experience and way of thinking.

Why to use a varistor instead of a diode?

MLV vs. TVS Diode

Varistor while being cheaper also has a smaller footprint and higher energy absorption capabilities. Smaller dimension with same characteristics as diodes. In constrast to a diode, however it has the same characteristics for both directions of traversing current.

Case size and energy capability comparison

The new varistors are therefore ideally suited for use in Internet of things (IoT) or Industry 4.0 applications.

Miniaturization is playing an increasingly crucial role in these applications too.

  1. TVS Diode DO-214AC, 18V, 102A
  2. MLV Varistor: equivalent over the size 2220, 18V, 1200A (10 x ImaxTVS)
  3. MLV Varistor: equivalent over the energy capability 0805, 18V, 120A

Performance at high temperature (i.e. Life Test for AEC-Q200)

In current market with continuous research of new products in all areas of application, quick response to provide customer product that is necessary for their product is crucial.

Market is changing rapidly and we are more than capable to adopt and follow any customers necessity with producing long lasting cooperation with customer.

Path forward

Innovative product is guaranteed with continuous testing procedures in all steps of product life (from design and development, through production time of product) tests are performed to establish product characteristics and quality level that will provide greatest characteristics in application through long period of time.

Performance at high temperature (i.e. Life Test for AEC-Q200)

MLV 1812, rated @ 150°C vs. MLV 1812, rated @ 85°C

Temperature: 150°C
Voltage: 85% Un
Time: 1000h

This example shows that the varistor rated at 150°C will be stable when exposed to the temperature of 150°C whereas the varistor rated at 125°C will slowly degrade when exposed to higher temperatures than rated.

Temperature stress test is one of the most important tests for determining the quality and stability of varistors. High temperatures slowly degrade the varistor – varistor nominal voltage (Un) decreases, leakage current (Idc) increases which will eventually cause the varistor to short itself out.

Performance at high temperature (i.e. Life Test for AEC-Q200)

MLV 1812, rated @ 150°C vs. MLV 1812, rated @ 85°C

Temperature: 150°C
Voltage: 85% Un
Time: 1000h

This example shows that the varistor rated at 150°C will be stable when exposed to the temperature of 150°C whereas the varistor rated at 125°C will slowly degrade when exposed to higher temperatures than rated.

Temperature stress test is one of the most important tests for determining the quality and stability of varistors. High temperatures slowly degrade the varistor – varistor nominal voltage (Un) decreases, leakage current (Idc) increases which will eventually cause the varistor to short itself out.

The lifetime of a varistor is determined by

Where A is the Aging factor and T0 is the Temperature Constant (T0=10°C)

Artificial aging temperature (acc. to AEC-Q200) is 125°C

Operating temperature of a varistor is 80°C

  • Testing conditions:
  • Time: 1000h
  • Voltage: 85% Un
  • The Aging factor is calculated as follows:

The lifetime of a varistor is then

This example shows the stability of a varistor – the varistor will be stable with the rate of degradation less than 10% during 7 years.

Let’s work together

High range of products already developed for various customer application is just one part of our approach to customer. We are opened and encourage cooperation with customer to achieve their needs regarding new products. This is achieved with our R&D department which is composed from experts in various field, working toward one goal – to develop and improve products in areas of function, safety and environment.

Repeatable transients are frequently caused by the operation of motors, generators, or the switching of reactive circuit components.
Disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction. The disturbance may degrade the performance of the circuit or even stop it from functioning.

A good example of a noise producing device is a brushcard motor (wiper, sunroof, seat adjuster..)

Causes are: sparks, insulation on comutator surface, relatively higher current at start of motor, etc.

What is RFI?

Electromagnetic interference (or EMI, also called radio frequency interference or RFI) is a disturbance that affects an electrical circuit due to either electromagnetic conduction or electromagnetic radiation emitted from an external source. The disturbance may interrupt, obstruct, or otherwise degrade or limit the effective performance of the circuit.

Differences between RFI/EMI

The terms EMI and RFI are often used interchangeably. EMI is actually any frequency of electrical noise, whereas RFI is a specific subset of electrical noise on the EMI spectrum. There are two types of EMI. Conducted EMI are unwanted high frequencies that ride on the AC wave form. Radiated EMI are similar to an unwanted radio broadcast being emitted from the power lines.

How do I know if I have RFI in my electrical system

If you are occasionally experiencing interference with your telephone system, flickering computer monitors, reliability issues with computer networks, instrumentation errors, or misbehaving electronics you are most likely experiencing RFI in your electrical environment. Since most devices have control electronic circuits, they may become difficult to control or unreliable. RFI disturbance may interrupt, obstruct, degrade or limit the effective performance of the circuit.

What is EMC?

EMC (Electromagnetic Compatibility)

An electronic or electrical product should work as intended in it’s environment. The electronic or electrical product shall not generate electromagnetic disturbances, which may influence other products. Most common standards are:

  • CISPR 25
  • IEC 61000
  • ISO 11452-1
  • EN 50 08

Quality First

Highly automated production process and equipment along with decades of production tradition guarantee premium quality products. This quality level supported by certificates and approvals such as AEC-Q200, IATF16949, VDE, UL enables Keko Varicon being an important supplier to a demanding automotive and other industries. With our desire to become partners to our customers, offering full technical and commercial support, we constantly seek for improvements and develop new products that will help solving our customers’ issues.

Quality standards are defined within the International Organization for Standardization and as such represent a base for defining processes which are robust and deliver products of highest quality.

ISO 9001 is base quality system management which is applicable for general products.
IATF 16949 is specifically determined to be applicable for all areas within automotive industry.

Additionally, third party certification schemes from various independent laboratories are valid in their respected areas of application as:

  • UL is a US standard for electronic components (covers also Canada),
  • VDE is a German standard for electronic components and
  • VDA is a German standard for automotive industry.

KEKO-Varicon proudly holds all relevant certificates which assures the base system is properly set up and quality products are produced and delivered. ISO 14001 is a standard which determines minimum requirements for handling of substances and energy and as such represent the base for overall ecological orientation of companies.

With long production tradition originating in 1960s, Keko Varicon is one of worldwide leaders in manufacturing of overvoltage protective and EMI suppression components (varistors and varistor-capacitor filters).

Get a download of Keko Varicon’s catalogues.

The long tradition and experience in the field of ceramic capacitor, most importantly, varistors, give the company Keko Varicon a certain advantage over most competing companies that are bigger in size, as it finds it easy to react to the buyer’s special requirements.