Question

When I use a relay card for drive control, it seems that my relays stick or do not operate correctly. How can I correct this problem?

Answer

Review the minimum load requirements of the PLC card or relays in question. The intelligent terminals of VFDs do not represent a significant load. If the drive's input terminal load does not meet or exceed the minimum requirements of the controller, then additional load will need to be added. A large resistor in parallel is usually the fix to this occurrence.

The smaller the relay, the more it is likely to have a minimum load requirement because of contact material and surface area contact. Each relay has a wiping current it must exceed to work properly. The requirements of gold contacts versus silver-tin-oxide contacts are enough to cause a problems in some cases.

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FAQ Subcategory: None

This item was last updated on 2007-09-25
Document ID: 890

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