AN3031

EMC requirements

Doc ID 16144 Rev 1

23/28

6

EMC requirements

6.1

Procedure to evaluate the robustness of the SCLT3-8BT8

The reference for evaluating the robustness of the SCLT3-8BT8 device is the IEC 61131-2

international standard. This international standard provides all requirements and test

conditions applicable to programmable logic controllers (PLCs) and their associated

peripherals.

The IEC 61131-2 standard specifies the electromagnetic compatibility (EMC) requirements

and the nature of the tests to perform in to determine if the system meets these

requirements. The levels of each test depend on the zone where the system will be installed.

The most typical industrial environmental levels correspond to zone B: local power

distribution zone and dedicated power distribution zone (see table 28: “EMC immunity

zones” of the IEC 61131-2-Ed2 standard). The following paragraphs recall the test levels for

this zone.

6.2

ESD tests (according to IEC 61000-4-2)

The electrostatic discharge test shall be applied to operator accessible devices. This means

that these tests have to be performed on each connector pin. The required levels are: air

discharge: ±8 kV contact discharge: ±4 kV.

The PLC system shall continue to operate as intended. Temporary degradation of the

performance is acceptable during the test, but the system must recover by itself after the

test (criteria “B” according to the IEC61131-2 standard).

6.3

Burst tests (according to IEC 61000-4-4)

The fast transient burst tests must be applied on all input pins of the system. A capacitive

clamp-coupling device (50-200 pF) must be used as described in the IEC 61000-4-4

standard. The required burst voltage levels are: analog or DC I/O: ±1 kV, DC power line: ±2

kV. The PLC system shall continue to operate as intended. Temporary degradation of the

performance is acceptable during the test, but the system must recover by itself after the

test (criteria “B” according to the IEC 61131-2 standard).

6.4

Surge test (according to IEC 61000-4-5)

Since the voltage surge consists of a single but energetic pulse, the SCLT3-8BT8 device

embeds an overvoltage protection on each point. The absorbed energy complies at least

with the requirements of the IEC 61131-2 standard. The high energy surge test must be

applied on all input pins of the system. For all analog inputs, the coupling method is a 42

Ω

serial resistor and a 0.5 µF capacitor. For DC power line, the coupling is 2

Ω, 18 µF with

differential mode, and 12

Ω, 9 µF with common mode. The required voltage surge levels are:

analog or DC I/O: 0.5 kV (line-to-line and line-to-earth coupling modes), DC power line: 0.5

kV (line-to-line), DC power line: 1 kV (line-to-earth). The PLC system shall continue to

operate as intended. Temporary degradation of the performance is acceptable during the

test, but the system must recover by itself after the test (criteria “B” according to the IEC

61131-2 standard).