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Why use interference suppression?
In the event that you use relays to switch loads, depending on the type used, they can cause an EMI (Electro Magnetic Interference). This can interfere with the proper operation of neighboring PLCs, gateways or other devices.
This EMI can become problematically large, for example, when switching multiple relays to distribute multiple heaters over different phases of the power grid, or when switching heavy 380V contactors. But even in lighter applications, caution is required!
Often this interference is also not always noticeable, or always present to the same degree, so determining the cause is not always straightforward. Indeed, a determining factor is the nature and condition of the load, as well as the timing of relay switching (in the case of switching the 50Hz power supply network).
You may have this problem when you notice unexplained device failures/defects, such as, for example (but not limited to):
- Failing USB connections between computer and peripherals.
- Short faltering HDMI connections.
- Audible interference on audio equipment.
- Faults in the operation of PLCs.
- Irregular restarting or reconnecting Calculus gateways.
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How to prevent EMI?
This failure can be prevented by:
On DC low voltage systems from 12-24V to opt for a relay with built-in varistor or other interference suppression. You can also buy a robust, prepared suppresion. Please contact your representative. This must then be placed over the solenoid of the relays (usually the A1 and A2 connections). And this as close as possible against the solenoid of the relays to work effectively.
In Calculus products such as the smart site cabin, this is provided by default as an add-on to the relays.
However, if our application switches on another relay of its own,
then be sure to provide it with its own interference suppression. These too
we gladly supply you with.
You can also buy a varistor yourself. A suitable suppressor for low voltage is the "ERZV10D101" of the brand Panasonic. This is for sale through this link: https://be.farnell.com/panasonic/erzv10d101/varistor-10mm-disc-100v/dp/1845438
Ask your representative about our offer for AC mains voltages of 230V. We offer a robust prepared module that ensures adequate interference suppression in most cases. This should also be placed as close as possible to and over the solenoid of the relay to be suppressed.
Don't have our article handy? Then you can e.g order Vishay's "VY2103M63Y5UG6TV7" from Farnell (https://be.farnell.com/vishay/vy2103m63y5ug6tv7/cap-0-01-f-20/dp/2860170) or another supplier. This is a "ceramic disc capacitor" of 10nF with a suppression class of X1/Y2 and a voltage rating of at least 300V.
Both solutions (like the relays themselves) are limited in their lifespan and are best replaced together in case of relay failure.
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Grounding the 12-24V power supply
In some cases, it is also appropriate to connect the GND or V- of the 12-24 Volt power supply being used to ground. This allows you to reduce the effect of disturbances moving through conductors. In our product the smart site cabin , a grounding terminal is specially provided for this purpose.
Please note! In temporary installations with sometimes questionable ground connections, this can cause an increase in faults or even failures. Therefore, proceed thoughtfully when grounding isolated power supplies.
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Basic rules when using a Calculus Gateway
To avoid interference on our gateways, apart from the above (highly recommended) interference suppression, we observe the following basic rules:
- Never place USB or other data cables close to a relay or control cabinet.
- Keep a distance of at least 10cm between Calculus gateways and relays.
Route power for a Calculus gateway and other connections always from each device separately and directly to the power supply through separate conductors.
Examples of other connections include:
- Output voltages.
- Relay voltages.
- Other devices connected to the same power supply.