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FAQ02098 of General Purpose Relays FAQ

FAQ No. FAQ02098

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Question

The Relay operates. However, there is no current flowing between the contact points. I want to know why.

Answer



The presumed reasons are as follows

(1) Transformation of Relay's internal components due to the shock of falling
The shock with which the Relay unit is dropped by mistake makes the internal components of the Relay transformed and then the connection between contact points unstable. Handle it with due care.

(2) Lifetime limitation due to contact erosion
Switching a load makes the contact points erode. When reaching the end of the working life, even if the Relay operates, the current flow becomes unstable. In this case, change the Relay.

(3) Loose contact points in minimum load switching
If a Relay with silver or silver-alloy contacts is used for minimum load switching, insulating capsules such as sulfureted one are easily produced, and then loose connection may be caused.
For minimum load switching, it is recommended to use a Relay with gold-plated cross-bar twin or twin contacts.

(4) Foreign body stuck between contact points
Especially with exposure types, if dusts, molding powders, wire debris or coating materials are stuck between contact points, it may cause loose connection. In this environment, it is recommended to use a Relay in a case.

(5) Loose contact points in inductive load switching
Carbon is produced by arc discharge generating between contact points in inductive load switching using solenoid or valve. Carbon accumulates on the surface of contact points, and thus the current flow may become unstable depending on an applied load. Surge protection suitable for the applied load is required.

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