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Siemens Industry Online Support
Siemens AG
Entry type: FAQ Entry ID: 109095117, Entry date: 03/05/2015
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Number of contacts connected in series (particularly control / auxiliary current circuit) on power and auxiliary contactors

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QUESTION:

How many auxiliary contacts may be connected in series on power and auxiliary contactors?

 

ANSWER:

Numerous electromechanical contacts which are connected in series entail a greater potential for malfunctions. As each contact point has a specific transition resistance, the summed up voltage drop of this “series connection“ may reach a value which can have a function-critical effect on specific loads or signal inputs.
In applications requiring a request of many contacts which are connected in series (e.g. in enable or emergency stop loops), you should adopt suitable measures in order to limit the number of contacts which are directly connected in series. For example on controllers, you could also distribute the row of contacts onto several inputs, or multiply the number of contacts in another way.
We cannot state the exact number of maximally permissible contacts which are connected in series, because this depends on numerous factors such as the current, voltage or other ambient conditions. On the basis of the experience made and the feedback provided from field engineers, a contact series connection of less than 10 contacts proved to be generally suitable.
In addition, you can increase the contact reliability of an individual contact by connecting a second contact in parallel.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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