EMC compatibility

FAQ #100161

 

Problem description with firmware version 2.1 and 2.2

All RAIL modules with firmware 2.1 and 2.2 can have a communication conflict. They have been de-livered approximately from June 2002 till now. The RAIL modules can stop their running mode and freeze itself in stop condition. The stopped mod-ule can only be reconditioned to running mode by a manual replacement of the power supply! The stopped working condition appears due to a new integrated processor that has a lower EMC (electro magnetic compatibility) tolerance than in module series with firmware lower 2.1. Modules with integrated new processor:

PCD7.L100 , PCD7.L110

PCD7.L121 (SAFE module with new functionalities)

PCD7.L200 

PCD7.L300, PCD7.L310

PCD7.L400

EMC compatibility

 Every RAIL and SAFE modules fulfil the standard DIN EN 61000-6-2 (interference resistance)! That means that the communication bus line is proved for an interference resistance +/- 1kV (capaci-tive load). Modules with firmware <2.1 with the former processor and less features had a tolerance in the inter-ference resistance up to approximately +/- 4kV (remember: the proved and official resistance is +/- 1kV). Modules with firmware 2.1 and 2.2 will actually interrupt the working condition if the EMC influence in the communication bus line is higher than 3 kV.

 Short term solution

 If there are some modules which indicate the described failure, the following improvements are possi-ble: 1. The bus line should be installed as described in the RS485 manual (26/740) to be sure that the bus line is free of any electromagnetic compatibility (EMC) influence. 2. With adding two external “Varistors” (Type: SIOV S07 K60) in the busline according to the drawing below at every single module, it is possible to increase the EMC interference resistance to +/ - 4.5kV.

 Varistor type: Disc-Varistor SIOV S07 K60

Possible Distributor: EPCOS AG (international) Homepage: www.epcos.com

Ordering code: B72207-S600-K101

Varistors are usually available in every electronic components store!

Important note:

With use of external Varistors is it possible that some S-Bus telegrams go lost. The higher the baudrate and the more bus members are involved, the higher the probability to loose telegrams.

Therefore we do not recommend to use a communication baudrate of 38’400 baud if the project has long distances, more than 50 S-Bus members and if external varistors are added!

Long term solution

The supplier BTR is about to improve the EMC interference resistance up to +/- 4.5kV of the module types mentioned above. This requires a modification of the module manufacturing process. The new modules will have an integrated interference resistance of around +/- 4.5kV without any restrictions.