Learn a little electromechanical knowledge every day, grow together and progress together. Contributions are welcome!
Each of us has touched and used electricity to the ground, but there are not many people who know about electricity. For some employees in the electrical industry. The electrical knowledge I know is not very comprehensive. Here we introduce the little electrical knowledge that seldom people pay attention to. Maybe it will bring some help to your future work.
1. Use category of circuit breaker
The use categories of circuit breakers are divided into CAT A and CAT B. The following figure shows CAT A molded case circuit breakers. CAT A circuit breakers are generally used as the incoming or terminal circuit breakers of the distribution cabinet. Generally, molded case circuit breakers are marked with CAT A. Molded case circuit breakers are more common, and careful friends should be able to notice.
CAT B circuit breakers are mainly used as the main switch for low-voltage incoming lines. Generally, air circuit breakers are mostly CAT B, which are generally installed in the power distribution cabinet of the power distribution room.
2. The description of the leakage protection function is usually expressed by RCBO, RCCB and RCD, but what is the difference between the three?
RCBO (Residual Current operated Cicuit-breaker with Integral Overcurrent protection) refers to a residual current operated circuit breaker that can perform overload and/or short circuit protection functions, such as an integrated leakage protection circuit breaker;
RCCB (Residual Current operated Circuit-breaker) refers to a residual current operated switch that cannot perform overload and/or short-circuit protection functions, that is, a leakage switch;
RCD (Residual Current Devices) refers to residual current operated protection devices whose detection, judgment and breaking functions are independent of the power supply voltage, such as residual current operated accessories.
3. What do the parameters 10/350 and 8/20 of the surge protector mean?
These two parameters describe the lightning current curve waveform. The two waveforms represent the curve of time and current. 10/350us is a typical lightning current curve when lightning penetrates the earth. It is a lightning current curve when lightning strikes power lines and lightning rods directly. It is generally called a direct lightning waveform.
8/20us is the electromagnetic pulse induced overvoltage caused by the lightning breakdown of the earth. The current curve when the induced overvoltage breaks down and burns the equipment is generally called the induced lightning waveform.
And the current value (how much kA) of the surge protector we often say is also based on the corresponding waveform.
4. What are the protection levels of high-voltage switchgear?
Do you know what the IP1X, IP2X, IP3X, IP4X, IP5X, IP6X protection levels mean? What is the main protection for each level?
The degree of protection refers to the degree of protection of the housing, partitions and other parts to prevent the human body from approaching live parts and touching moving parts, as well as preventing external objects from entering the internal equipment.
IP1X protects objects with a diameter greater than 50mm, and mainly protects solid bodies and large parts of the human body with a diameter greater than 50mm from touching live parts in the cabinet.
IP2X protects objects with a diameter greater than 12.5mm, and mainly protects solid objects with a diameter greater than 12.5mm and hand-touched live parts in the cabinet.
IP3X protects objects with a diameter greater than 2.5mm, and mainly protects solid and metal wire cabinets with a diameter greater than 2.5mm.
IP4X protects objects with a diameter greater than 1mm, and mainly protects solid and metal wire cabinets with a diameter greater than 1mm.
IP5X dust-proof, mainly to prevent dust from entering the shell, and fully protect the live parts in the cabinet.
IP6X is the highest dust-tight protection level, completely preventing dust and complete protection from touching the live parts in the cabinet.
Knowing the knowledge of high-voltage switchgear protection cold will let you know more clearly what level of high-voltage switchgear you need. Prevent being fooled into buying high-voltage switchgear that is not needed at all.
5. What is the cause of the “buzzing” noise during operation of the transformer?
Although it is noise, if it is not resolved for a long time, it will surely fail over time.
It is mainly produced by the hysteresis of the iron core piece in the iron core (the iron core with air gap and electromagnetic force). In addition, the electromagnetic force of the winding and the transmission of transformer related accessories (including resonance) can also cause noise.
To deal with the problem of excessive noise in the transformer on site, you must first carefully analyze the source of the sound. Generally, dry-type transformers often generate noise due to the resonance of the body and shell. In a few cases, the noise is caused by abnormal loosening of fasteners;
For these two situations, the fasteners of the transformer (screws, spacers, foot bolts, connecting bolts of the housing, foreign objects falling into the fan, centrifugal swing of the fan rotor, bolts on the bottom net of the housing, or loose bolts, etc.) Carry out a comprehensive inspection and re-tighten it in place, tighten the resonance-generated parts or install a vibration reduction device (pad rubber) to reduce and eliminate noise.
