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Determining the classification of molded case circuit breakers is particu

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Determining the classification of molded case circuit breakers is particu

2024-06-28

Determining the classification of molded case circuit breakers is particularly important for molded case circuit breaker selection

 First, let’s understand the classification of molded case circuit breakers. There are three types of circuit breakers currently available on the market:
 1. Distribution type: It is mainly used for overload and short-circuit protection of low-voltage lines. Typical products include TXM1 series, DZ20, DZ15 series, DZ20Y, DZ10 series, etc. The standard they comply with is GB14048.2 or IEC947-2.
 2. Motor protection type. It is used for motor overload and short-circuit protection. There are motor protection types in type 1, small-capacity motor protection special type DZ15LD series, etc. It meets the standards of GB14048.2 and GB14048.4.
 3. For household use and similar places, there are DZ108DZ10DZ15, etc., and the standards are GB10963 or IEC898. Since the loads carried by the places of use are different, they have their own overload and short-circuit characteristics and cannot be confused. In particular, please note: some users often use the distribution type to protect the motor. This is a wrong understanding.

 Next, understand the application places and selection principles of molded case circuit breakers.
 1. In high-temperature places such as ironmaking, casting molding, boiler rooms and other places, pure electromagnetic types that are not affected by temperature should be used (but not too high). For thermal-electromagnetic types, when the temperature is 40°-60°, the temperature should be reduced. It can be used, but cannot be used when the temperature is above 60°.
 2. Low temperature places. Refers to places below -5°, such as refrigerated warehouses, low-temperature rooms, foggy decks of ships, etc. If the temperature is too low, the lubricant will dry up and the insulation parts will become brittle, so users should order low-temperature circuit breakers.
 3. Humid places. Refers to relatively humid places such as chemical plants, fish processing plants, etc. The circuit breaker should be installed in a waterproof box. If it is not in direct contact with water, a humid tropical type molded case circuit breaker should be used.
 4. Dusty places. For example, in cement factories and textile factories, circuit breakers can be installed in dust-proof boxes.
 5. Coal mines and other mines. A circuit breaker with a voltage level of 660V can be selected and placed in an explosion-proof box.
 6. Ships. General civilian transport ships should use marine molded case circuit breakers with three protections (moisture-proof, mildew-proof, and salt spray-proof) and a certain level of resistance to vibration, bumping, and tilting. The base temperature is 45°. For ships, except for civilian ships (seismic resistance, Requirements for bumps and tilts**), first-level impact resistance, and a base temperature of 50°.
 7. Electric locomotives. It is similar to the one used on ships, but it does not necessarily require three defenses.
 8. Places with corrosive gases and salt spray. In places such as chemical plants, pharmaceutical plants, petroleum refineries, etc., corrosion-resistant molded case circuit breakers should be used and installed in waterproof boxes.
 Finally, the general installation method of molded case circuit breakers is vertical installation. So can it be installed horizontally or horizontally? The test results show that when the thermal-electromagnetic molded case circuit breaker is installed horizontally or horizontally, it has almost no impact on overload protection. For the reaction spring (related to gravity) of the electromagnet of the instantaneous release, the test value is only 5-10% error, so the conclusion is: it can be installed horizontally or horizontally.
 For a purely electromagnetic or hydraulic (oil cup type) molded case circuit breaker, its overload and short-circuit protection use the same release device, and its overcurrent delay or smooth movement is related to the center of gravity and damping of the iron core in the oil pipe ( Delay) has a great relationship with the silicone oil level, and these are related to the installation angle. Tests show that the action value (current value) of 2In should be increased by 20% when installed horizontally, reduced by 20% when installed counter-horizontally, and reduced by 12% when tilted forward at 45°. Therefore, pure electromagnetic circuit breakers should be installed vertically. If they must be installed horizontally or horizontally, the current value should be determined based on the correction coefficient provided by relevant information.