how to check the quality of miniature circuit breaker (mcb)
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What you can expect to learn insideToday we are not talking about checking by manufacturers, this article (How to Check the Quality of MCB Circuit Breaker PDF) is about helping you, the buyer, check the quality of the MCB electrical before its delivery. This will be different from routine check and final confirmation check and some manufacturers may be not keen to provide this information. The checking includes:Appearance examinationExternal and internal main material inspectionMechanical operationPerformance inspection1) Delay test-1.13In2) Delay test-1.45In3) Delay test-2.55In 4) Instantaneous test 5) Power-frequency withstand voltage testExcerptThe quality of the MCB circuit breaker is very important. This decides its performance, life and even the safety of the users. Normally we would carry out both a routine check and final confirmation check for miniature circuit breakers before their delivery.However today we are not talking about checking by manufacturers, this article is about helping you, the buyer, check the quality of the MCB electrical before its delivery. This will be different from routine check and final confirmation check and some manufacturers may be not keen to provide this information.The checking includes an appearance examination, external and internal material inspection, mechanical operation and performance inspection. Now let’s make the analysis of MCB circuit breaker SLB1-63 for the example.TRANSCRIPT
MCB CircuitBreaker
the quality ofHow to check
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How To Check The Quality of MCB Circuit Breaker
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1. Appearance examination
a. Plastic parts should be clean and without damage and defects, such as cracks or air bubbles on surface (check picture 1).
b. Anti-corrosion coating of the exposed metal parts should be glossy and without obvious pinhole, dots, bubble, black, etc.
c. The content and colors of the printing should be complying with the drawing if it has no obvious defects (check picture 2).
d. After circuit breaker base is covered, the juncture should be flat and aligned, the rivet should be fixed tightly (check picture 3).
The quality of the MCB circuit breaker is very important. This decides its performance, life and even the safety of the users. Normally we would carry out both a routine check and final confirmation check for miniature circuit breakers before their delivery.
However today we are not talking about checking by manufacturers, this article is about helping you, the buyer, check the quality of the MCB electrical before its delivery. This will be different from routine check and final confirmation check and some manufacturers may be not keen to provide this information.
The checking includes an appearance examination, external and internal material inspection, mechanical operation and performance inspection. Now let’s make the analysis of MCB circuit breaker SLB1-63 for the example.
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How To Check The Quality of MCB Circuit Breaker
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2. External and internal main material inspection
Our MCB breaker SLB1-63 is made of material nylon PA66. Check if the factory used the material you appointed for the circuit breaker case (check picture 4).
a. Nylon is the normal material for MCB circuit breakers, among which PA66 and PA6 is used mostly. PA66 is better than PA6 regarding flame resistance, color and working life, etc. Breaker case made of PA66 will stop burning if away from fire; case of PA66 has brighter color and longer using life. There is also a better Mitsubishi nylon for choice if required.
b. Some manufacturers may use recycled material fully or partially in order to reduce the cost. The miniature circuit breaker completely made of new material is bright, glossy, without black spots, whereas the one made of recycled material is darker and less glossy. Used PA6 is mostly applied in the case production, by some manufacturers.
c. Weigh the case and compare if the weight is same as the sample’s, which is confirmed by both parties before production.
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Coil and wire of SLB1-63 is made of red copper, with coils of 1.13mm*10 for 10A, and 2.4mm*5mm*2 for 63A. Different coils are applied for different ratings. Check if the factory used the material and thickness you want for them (check picture 5).
a. Some manufacturers use brass instead of red copper to reduce the cost, they are different in colors. Some manufacturers even apply CCA and iron for coil and wire, CCA can be judged through its section, iron can be attracted by magnets.
b. If the factory has already used the material you want for coil and wire, now you have to check its thickness to confirm if it is thick enough for your current rating. Some producers may reduce a wire’s thickness to decrease its cost. You can completely measure its thickness to confirm this.
MCB electrical SLB1-63 uses red copper for its moving and fixed contacts, terminals and iron for its big support. Some factories use brass or iron instead, but iron does not weld well.
Contact on bi-metal strip of mini circuit breaker SLB1-63 is made of red copper for current less than 50A and compound silver contactor for more than 50A. However, some manufacturers employ brass and iron instead, as there is a big difference in costs. You can judge through colors (check picture 6).
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3. Mechanical operation
5 cycling operations between switching on and off should be flexible and reliable, without jammed and sliding phenomenon.
4. Performance inspection
Actually all the miniature circuit breakers have been inspected by the factory before their delivery, so you only need to randomly select some for the performance inspection.
Manufacturers generally carry out these tests strictly according to relative standard, so we will not show you here in detail. Performance inspection includes delay test, instantaneous test, power-frequency withstand voltage test, etc. Here all the tests as below are referring to standard GB10963 and IEC60898.
Delay test-1.13In
Check if the breaker trips within 1 hour. If it tripped, or burned without tripping, it will be judged as an unqualified item.
Delay test-1.45In
The MCB breaker must trip within 30 minutes. If it didn’t trip, or damaged with tripping, it will be judged as an unqualified item.
Delay test-2.55In
MCB circuit breakers of 1~32A should trip between 1s~60s, MCB breakers of 40~63A should trip between 1s~120s. Each pole should be energized if it is a multi-pole MCB (If just one pole for testing, upper limit of tripping time should be 1.1 times upper ends above.)
If circuit breaker didn’t trip, or burned with tripping, it is judged as unqualified item.
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How To Check The Quality of MCB Circuit Breaker
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Instantaneous test
Characteristic Input current Tripping time
C 5In >0.1s
C 10In <0.1s
D 10In >0.1s
D 20In <0.1s
MCB should trip within stipulated time. If MCB didn’t trip, or burned with tripping, it will be judged as an unqualified item.
Power-frequency withstand voltage test
There is no breakdown and flashover phenomenon under condition of 2000V, threshold value 100mA, 50Hz, 1 minute, at points as below:
– Between incoming and outgoing terminals of each poles, with breaker switched off
– Between poles with breaker switched on
– Between poles and case, with breaker switched on
With a list of tests carried out above, you can decide if this batch of breakers is qualified or not, if unqualified, inform the factory regarding the points which should be improved.
Manufacturers can’t hide anything from you once you know how to check the quality of MCB circuit breaker. It is best to appoint the material for key parts in the contract! And also remember: you always get what you pay for!
Guangzhou Shilin Electrical Co., Ltd.Ershe Industrial Zone, Daxiang Village, Renhe Town, Baiyun District,
Guangzhou City, Guangdong Province, China
TEL: 0086-20-86033123 | FAX: 0086-20-86033163 | CELL: [email protected] | www.miniature-circuit-breaker.com
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