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What is the reason of having an unstable terminal voltage on the loosely connected 2 or 3-pole circuit breaker terminals?

When one or more terminals of a230V or415V circuit breaker is loosely or poorly connected to an electrical circuit, you might get a different voltage values using a multi-tester every time you will make a test reading. What is caused by this instances?

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Question added by Tom Escosa , HVAC Engineer , ADNOC
Date Posted: 2013/10/18
Ramendra Sunder Sinha PMP
by Ramendra Sunder Sinha PMP , DGM Planning , Gaur Sons Limited

Loose contacts result in air gap. Air contains CO2 which converts to carbon during arcing and this carbon deposit on the current path increases the resistance. This causes voltage drop due to IR losses.

Compounding to this there is local heating of conductors close to the loose contacts and this further increase the resistance as resistance increases with increase in temperature.

Typically such problems have a cascading effect which over time may lead to frequent tripping of the Circuit Breaker and permanent fault and can even result in damage or derating of the Circuit Breaker which may have to be replaced.

Deleted user
by Deleted user

If the Terminals are Loosely connected the potential difference between the two terminals are varies, Hence there is a voltage drop ,the current will increases and the loosed terminal get burnt...

 

Raheel Rehman
by Raheel Rehman , Civil Engineer , Mosasa Zaid Alshahri

The loose connections may cause sparks  upon load on that wire,  If the wire is half connected then it will create air gap,  as Ramindera Sunder said above, and as we all know that wire consist copper and in open air, if there is copper then it will turn into copper sulphate, we usually call it salt, and due to loose connection, the wire will get hot upon load, so the heat will make the carbon and that carbon will cause resistance. An electrician can cut the wire and make a new connection, or simply rub the end with sand paper.

spend some time to tighten the connection you will find every thing is ok

ZIA UL HAQ IBRAMSHA
by ZIA UL HAQ IBRAMSHA , Technical Engineer (Electrical Engineering) , Saudi Awtad Mechanical Electrical Company (SAME),

LOOSE CONNECTION WILL LEADS TO PASS OVER CURRENT AND VOLTAGE DROP. SO THE TERMINAL VOLTAGE IS UNSTABLE.

Aftab Ahmed
by Aftab Ahmed , Senior Engineer- Technical Service and Coordination Department , Pakistan Oilfields Ltd (POL)

In Question, there is already an answer present.

 

Loosely connected means circuit Impedence Balance shall be disturbed & hence the Voltages.

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