Kühn Controls

General information about COMAT and MULTICOMAT Relays



There are several different types of contact materials for COMAT relays.
The main distinction can be made between single contacts and twin contacts.
While single contacts are more suitable for higher loads, twin contacts are significantly more reliable for low switching loads, i.e. < 24V, < 100mA.

Contact material

There is no all-purpose universal contact.
AgNi  is used as a standard contact material for a wide range of applications.
For applications in aggressive atmospheres, AgNi contacts with hard gold plating (up to 10µm) are recommended.
There is however no other purpose then corrosion protection during storage.
COMAT Relays with tungsten pre-contacts are available for very high switching currents (up to 500A, 2.5ms).

Minimum load

The minimum load values are recommended values under normal working conditions i.e. regular switching, no special ambient conditions, etc.
Under these conditions reliable switching can be expected.

Contact resistance

In practice the contact resistance may vary depending on the switching load and other environmental conditions.
For higher currents the contact resistance is around 10mΩ.

Contact spacing

Normally all open contacts have an air gap between 0,5 … 1,5mm.
They are referred to as µ contacts according to the Low-Voltage Directives and associated standards.
These contacts are not suitable for safe disconnection.
For switching of DC loads, large contact clearances are requested for the quenching of the electric arcs. (Pls. refer to special relays: Series connections.)

Switching capacity

The contact switching capacity is the product of switching voltage and switching current.
For AC, the permitted switching capacity is generally enough to handle the max. continuous AC1 current over the whole voltage range.
It is not allowed to exceed the load limit curve for DC switching because a remaining switch-off-arc would destroy the relay immediately.
The DC switching capacity is 100W (DC 1).

Drive (coil)

A distinction is made between standardized voltages according to EN 60947 as guaranteed values, and typical values which can be expected with a high degree of probability.

Pick-up voltage, Release voltage

The pick-up voltage is the voltage at which the relay engages safely.
The typical trip voltage for DC is approx. 65% of Unom. and approx. 75% of Unom. for AC.
The release voltage is approx. 25%, resp. 60% of Unom.
For DC, these voltages depend strongly on the temperature coefficient for Cu.
This is however not the case for AC, where the constant inductive resistance over a wide temperature range is the controlling factor.
Under voltages in AC relays results in humming and armature fluttering and should therefore be avoided.

Operating voltage range

The upper voltage limit of the coil is determined by the heat and the ambient temperature.
The self-heating trough the contacts under high loads should not be underestimated since it may even be higher than the dissipated energy of the coil.
Significantly high but short period overvoltage however provides no problem for intermittent operations.
In doubt please consult our specialist or ask for the respective characteristic curve diagram.

Coil connections

Different coil connections can be integrated into the relay as an option.
A cost effective freewheeling diode is available for DC coils. Please note that the stated release times are generally specified without the coil connection.
While an additional LED status indicator has practically no effect, a freewheeling diode (D) will lead to an increase in release time by a factor 2 to 5, or 0 ms to 30ms.
For AC coils, VDRs or RC elements may be used. In this case resonance effects may have to be considered. VDRs and common RC elements may increase release times by < 5ms.

General design

Comat relays are made from carefully selected high-quality materials.
The components comply with the latest environmental regulations such as RohS.
The meticulous design makes the relays particularly suitable for any industrial application and engineering installation.
The robust terminals, mechanical position indicator, dynamic and permanent hand activators, all integrated in the standard relay make them particularly service friendly.
Colour coded hand test buttons dependent on the type of coil voltage is another useful feature.

Options of COMAT Relays:
- Different coil connections
- Freewheeling diodes
- LED displays
- Bridge rectifiers for AC/DC drives, etc.
Additionally, because of short-term availability of special versions for practically any drive voltage up to DC 220V/AC 400V the relays are a cost effective solution for many applications
For safety reasons, manual operated test buttons may be replaced with a blank button, if required.

Further information

To select the most suitable COMAT relay and to guarantee a reliable operation and a long service life for the application, several factors need to be considered.
In particular these are:
- Number of cycles
- Switching frequency
- Ambient conditions
- Load type
- Switch-on current and load switch-off energy.


If the number of cycles are expected to exceed > 100,000 operations per year.
(E.g. clock generators, fast running machines), an electronic solution is perhaps more appropriate.
Comat is able to offer a suitable relay from our standard product range.
In AC applications, crosstalk caused by long control leads is often a problem and can result in constant humming of the relay or even inadvertent triggering due to interference.
Here too, we offer solutions.
Various, apparently harmless loads may lead to very high switch-on currents or switch-off energy values This may result in an unacceptable reduction of the service life.
Inductive DC loads are especially harmful.

Characteristics of various loads:

Heating circuits

No high switch-on currents, no high switch-off loads.

Incandescent lamps, halogen lamps

Switch-on currents during a few ms in the range 10 x rated IN. Switch-off at rated load.

Low-energy lamps

Very high, with very short switch-on currents due to built-in decoupling capacitors.
Contacts have a tendency to fuse.

Transformers, AC contactors

Switching on during zero-transition may avoid high inrush currents.
If switching before or after the zero crossing, switch-on currents of 8…15 x rated IN. may occur.
High inductive switch-off energy is possible. The load must be wired, due to EMC problems.

COMAT and MULTICOMAT Relays, data sheets and product information.

Approvals, Certificates, Approbations about COMAT and MULTICOMAT Relays.

You want more informations about COMAT and MULTICOMAT, Please send us a fax: +49 7082 940001, or email to: Inquiry to Kühn Controls… we help you…

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